/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 * Port to the D programming language:
 *     Frank Benoit <benoit@tionex.de>
 *******************************************************************************/
module org.eclipse.swt.widgets.Tree;



import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTException;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.events.TreeListener;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.Font;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.internal.gtk.OS;
import org.eclipse.swt.widgets.TreeItem;
import org.eclipse.swt.widgets.TreeColumn;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.ImageList;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Decorations;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.ScrollBar;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.TypedListener;
import java.lang.all;

/**
 * Instances of this class provide a selectable user interface object
 * that displays a hierarchy of items and issues notification when an
 * item in the hierarchy is selected.
 * <p>
 * The item children that may be added to instances of this class
 * must be of type <code>TreeItem</code>.
 * </p><p>
 * Style <code>VIRTUAL</code> is used to create a <code>Tree</code> whose
 * <code>TreeItem</code>s are to be populated by the client on an on-demand basis
 * instead of up-front.  This can provide significant performance improvements for
 * trees that are very large or for which <code>TreeItem</code> population is
 * expensive (for example, retrieving values from an external source).
 * </p><p>
 * Here is an example of using a <code>Tree</code> with style <code>VIRTUAL</code>:
 * <code><pre>
 *  final Tree tree = new Tree(parent, SWT.VIRTUAL | SWT.BORDER);
 *  tree.setItemCount(20);
 *  tree.addListener(SWT.SetData, new Listener() {
 *      public void handleEvent(Event event) {
 *          TreeItem item = (TreeItem)event.item;
 *          TreeItem parentItem = item.getParentItem();
 *          String text = null;
 *          if (parentItem is null) {
 *              text = "node " + tree.indexOf(item);
 *          } else {
 *              text = parentItem.getText() + " - " + parentItem.indexOf(item);
 *          }
 *          item.setText(text);
 *          System.out.println(text);
 *          item.setItemCount(10);
 *      }
 *  });
 * </pre></code>
 * </p><p>
 * Note that although this class is a subclass of <code>Composite</code>,
 * it does not normally make sense to add <code>Control</code> children to
 * it, or set a layout on it, unless implementing something like a cell
 * editor.
 * </p><p>
 * <dl>
 * <dt><b>Styles:</b></dt>
 * <dd>SINGLE, MULTI, CHECK, FULL_SELECTION, VIRTUAL, NO_SCROLL</dd>
 * <dt><b>Events:</b></dt>
 * <dd>Selection, DefaultSelection, Collapse, Expand, SetData, MeasureItem, EraseItem, PaintItem</dd>
 * </dl>
 * </p><p>
 * Note: Only one of the styles SINGLE and MULTI may be specified.
 * </p><p>
 * IMPORTANT: This class is <em>not</em> intended to be subclassed.
 * </p>
 *
 * @see <a href="http://www.eclipse.org/swt/snippets/#tree">Tree, TreeItem, TreeColumn snippets</a>
 * @see <a href="http://www.eclipse.org/swt/examples.php">SWT Example: ControlExample</a>
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 */
public class Tree : Composite {

    alias Composite.computeSize computeSize;
    alias Composite.createHandle createHandle;
    alias Composite.dragDetect dragDetect;
    alias Composite.mnemonicHit mnemonicHit;
    alias Composite.mnemonicMatch mnemonicMatch;
    alias Composite.setBackgroundColor setBackgroundColor;
    alias Composite.setBounds setBounds;

    CallbackData treeSelectionCallbackData;
    GtkTreeStore* modelHandle;
    GtkCellRenderer* checkRenderer;
    int columnCount, sortDirection;
    GtkWidget* ignoreCell;
    TreeItem[] items;
    TreeColumn [] columns;
    TreeColumn sortColumn;
    TreeItem currentItem;
    ImageList imageList, headerImageList;
    bool firstCustomDraw;
    bool modelChanged;
    bool expandAll;
    int drawState, drawFlags;
    GdkColor* drawForeground;
    bool ownerDraw, ignoreSize;

    static const int ID_COLUMN = 0;
    static const int CHECKED_COLUMN = 1;
    static const int GRAYED_COLUMN = 2;
    static const int FOREGROUND_COLUMN = 3;
    static const int BACKGROUND_COLUMN = 4;
    static const int FONT_COLUMN = 5;
    static const int FIRST_COLUMN = FONT_COLUMN + 1;
    static const int CELL_PIXBUF = 0;
    static const int CELL_TEXT = 1;
    static const int CELL_FOREGROUND = 2;
    static const int CELL_BACKGROUND = 3;
    static const int CELL_FONT = 4;
    static const int CELL_TYPES = CELL_FONT + 1;

/**
 * Constructs a new instance of this class given its parent
 * and a style value describing its behavior and appearance.
 * <p>
 * The style value is either one of the style constants defined in
 * class <code>SWT</code> which is applicable to instances of this
 * class, or must be built by <em>bitwise OR</em>'ing together
 * (that is, using the <code>int</code> "|" operator) two or more
 * of those <code>SWT</code> style constants. The class description
 * lists the style constants that are applicable to the class.
 * Style bits are also inherited from superclasses.
 * </p>
 *
 * @param parent a composite control which will be the parent of the new instance (cannot be null)
 * @param style the style of control to construct
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
 *    <li>ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass</li>
 * </ul>
 *
 * @see SWT#SINGLE
 * @see SWT#MULTI
 * @see SWT#CHECK
 * @see SWT#FULL_SELECTION
 * @see SWT#VIRTUAL
 * @see SWT#NO_SCROLL
 * @see Widget#checkSubclass
 * @see Widget#getStyle
 */
public this (Composite parent, int style) {
    super (parent, checkStyle (style));
}

override void _addListener (int eventType, Listener listener) {
    super._addListener (eventType, listener);
    if (!ownerDraw) {
        switch (eventType) {
            case SWT.MeasureItem:
            case SWT.EraseItem:
            case SWT.PaintItem:
                ownerDraw = true;
                recreateRenderers ();
                break;
            default:
        }
    }
}

TreeItem _getItem (GtkTreeIter* iter) {
    int id = getId (iter, true);
    if (items [id] !is null) return items [id];
    auto path = OS.gtk_tree_model_get_path (modelHandle, iter);
    int depth = OS.gtk_tree_path_get_depth (path);
    int [] indices = new int [depth];
    indices[] = OS.gtk_tree_path_get_indices (path)[ 0 .. depth ];
    GtkTreeIter* parentIter;
    GtkTreeIter parentIterInst;
    if (depth > 1) {
        OS.gtk_tree_path_up (path);
        parentIter = &parentIterInst;
        OS.gtk_tree_model_get_iter (modelHandle, parentIter, path);
    }
    items [id] = new TreeItem (this, parentIter, SWT.NONE, indices [indices.length -1], false);
    OS.gtk_tree_path_free (path);
    return items [id];
}

TreeItem _getItem (GtkTreeIter* parentIter, int index) {
    GtkTreeIter iter;
    OS.gtk_tree_model_iter_nth_child(modelHandle, &iter, parentIter, index);
    int id = getId (&iter, true);
    if (items [id] !is null) return items [id];
    return items [id] = new TreeItem (this, parentIter, SWT.NONE, index, false);
}

int getId (GtkTreeIter* iter, bool queryModel) {
    if (queryModel) {
        int value;
        OS.gtk_tree_model_get1 (modelHandle, iter, ID_COLUMN, cast(void**)&value);
        if (value  !is -1) return value ;
    }
    // find next available id
    int id = 0;
    while (id < items.length && items [id] !is null) id++;
    if (id is items.length) {
        TreeItem [] newItems = new TreeItem [items.length + 4];
        System.arraycopy (items, 0, newItems, 0, items.length);
        items = newItems;
    }
    OS.gtk_tree_store_set1 (modelHandle, iter, ID_COLUMN, cast(void*)id );
    return id;
}

static int checkStyle (int style) {
    /*
    * Feature in Windows.  Even when WS_HSCROLL or
    * WS_VSCROLL is not specified, Windows creates
    * trees and tables with scroll bars.  The fix
    * is to set H_SCROLL and V_SCROLL.
    *
    * NOTE: This code appears on all platforms so that
    * applications have consistent scroll bar behavior.
    */
    if ((style & SWT.NO_SCROLL) is 0) {
        style |= SWT.H_SCROLL | SWT.V_SCROLL;
    }
    /* GTK is always FULL_SELECTION */
    style |= SWT.FULL_SELECTION;
    return checkBits (style, SWT.SINGLE, SWT.MULTI, 0, 0, 0, 0);
}

override void cellDataProc (
    GtkTreeViewColumn *tree_column,
    GtkCellRenderer *cell,
    GtkTreeModel *tree_model,
    GtkTreeIter *iter,
    void* data)
{
    if (cell is cast(GtkCellRenderer*)ignoreCell) return;
    TreeItem item = _getItem (iter);
    if (item !is null) OS.g_object_set_qdata (cast(GObject*)cell, Display.SWT_OBJECT_INDEX2, item.handle);
    bool isPixbuf = OS.GTK_IS_CELL_RENDERER_PIXBUF (cell);
    if (!(isPixbuf || OS.GTK_IS_CELL_RENDERER_TEXT (cell))) return;
    int modelIndex = -1;
    bool customDraw = false;
    if (columnCount is 0) {
        modelIndex = Tree.FIRST_COLUMN;
        customDraw = firstCustomDraw;
    } else {
        TreeColumn column = cast(TreeColumn) display.getWidget (cast(GtkWidget*)tree_column);
        if (column !is null) {
            modelIndex = column.modelIndex;
            customDraw = column.customDraw;
        }
    }
    if (modelIndex is -1) return;
    bool setData = false;
    if ((style & SWT.VIRTUAL) !is 0) {
        /*
        * Feature in GTK.  On GTK before 2.4, fixed_height_mode is not
        * supported, and the tree asks for the data of all items.  The
        * fix is to only provide the data if the row is visible.
        */
        if (OS.GTK_VERSION < OS.buildVERSION (2, 3, 2)) {
            auto path = OS.gtk_tree_model_get_path (tree_model, iter);
            OS.gtk_widget_realize (handle);
            GdkRectangle visible;
            OS.gtk_tree_view_get_visible_rect (handle, &visible);
            GdkRectangle area;
            OS.gtk_tree_view_get_cell_area (handle, path, tree_column, &area);
            OS.gtk_tree_path_free (path);
            if (area.y + area.height < 0 || area.y + visible.y > visible.y + visible.height ) {
                /* Give an image from the image list to make sure the row has
                * the correct height.
                */
                if (imageList !is null && imageList.pixbufs.length > 0) {
                    if (isPixbuf) OS.g_object_set1 (cell, OS.pixbuf.ptr, cast(ptrdiff_t)imageList.pixbufs [0]);
                }
                return;
            }
        }
        if (!item.cached) {
            //lastIndexOf = index [0];
            setData = checkData (item);
        }
    }
    void* ptr;
    if (setData) {
        if (isPixbuf) {
            ptr = null;
            OS.gtk_tree_model_get1 (tree_model, iter, modelIndex + CELL_PIXBUF, &ptr);
            OS.g_object_set1 (cell, OS.pixbuf.ptr, cast(ptrdiff_t)ptr);
        } else {
            ptr = null;
            OS.gtk_tree_model_get1 (tree_model, iter, modelIndex + CELL_TEXT, &ptr);
            if (ptr !is null) {
                OS.g_object_set1 (cell, OS.text.ptr, cast(ptrdiff_t)ptr);
                OS.g_free (ptr);
            }
        }
    }
    if (customDraw) {
        /*
         * Bug on GTK. Gtk renders the background on top of the checkbox and pixbuf.
         * This only happens in version 2.2.1 and earlier. The fix is not to set the background.
         */
        if (OS.GTK_VERSION > OS.buildVERSION (2, 2, 1)) {
            if (!ownerDraw) {
                ptr = null;
                OS.gtk_tree_model_get1 (tree_model, iter, modelIndex + CELL_BACKGROUND, &ptr);
                if (ptr !is null) {
                    OS.g_object_set1 (cell, OS.cell_background_gdk.ptr, cast(ptrdiff_t)ptr);
                }
            }
        }
        if (!isPixbuf) {
            ptr = null;
            OS.gtk_tree_model_get1 (tree_model, iter, modelIndex + CELL_FOREGROUND, &ptr);
            if (ptr !is null) {
                OS.g_object_set1 (cell, OS.foreground_gdk.ptr, cast(ptrdiff_t)ptr);
            }
            ptr = null;
            OS.gtk_tree_model_get1 (tree_model, iter, modelIndex + CELL_FONT, &ptr);
            if (ptr !is null) {
                OS.g_object_set1 (cell, OS.font_desc.ptr, cast(ptrdiff_t)ptr);
            }
        }
    }
    if (setData) {
        ignoreCell = cast(GtkWidget*)cell;
        setScrollWidth (tree_column, item);
        ignoreCell = null;
    }
}

bool checkData (TreeItem item) {
    if (item.cached) return true;
    if ((style & SWT.VIRTUAL) !is 0) {
        item.cached = true;
        TreeItem parentItem = item.getParentItem ();
        Event event = new Event ();
        event.item = item;
        event.index = parentItem is null ? indexOf (item) : parentItem.indexOf (item);
        int mask = OS.G_SIGNAL_MATCH_DATA | OS.G_SIGNAL_MATCH_ID;
        int signal_id = OS.g_signal_lookup (OS.row_changed.ptr, OS.gtk_tree_model_get_type ());
        OS.g_signal_handlers_block_matched (modelHandle, mask, signal_id, 0, null, null, handle);
        currentItem = item;
        sendEvent (SWT.SetData, event);
        currentItem = null;
        //widget could be disposed at this point
        if (isDisposed ()) return false;
        OS.g_signal_handlers_unblock_matched (modelHandle, mask, signal_id, 0, null, null, handle);
        if (item.isDisposed ()) return false;
    }
    return true;
}

protected override void checkSubclass () {
    if (!isValidSubclass ()) error (SWT.ERROR_INVALID_SUBCLASS);
}

/**
 * Adds the listener to the collection of listeners who will
 * be notified when the user changes the receiver's selection, by sending
 * it one of the messages defined in the <code>SelectionListener</code>
 * interface.
 * <p>
 * When <code>widgetSelected</code> is called, the item field of the event object is valid.
 * If the receiver has the <code>SWT.CHECK</code> style and the check selection changes,
 * the event object detail field contains the value <code>SWT.CHECK</code>.
 * <code>widgetDefaultSelected</code> is typically called when an item is double-clicked.
 * The item field of the event object is valid for default selection, but the detail field is not used.
 * </p>
 *
 * @param listener the listener which should be notified when the user changes the receiver's selection
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see SelectionListener
 * @see #removeSelectionListener
 * @see SelectionEvent
 */
public void addSelectionListener (SelectionListener listener) {
    checkWidget ();
    if (listener is null) error (SWT.ERROR_NULL_ARGUMENT);
    TypedListener typedListener = new TypedListener (listener);
    addListener (SWT.Selection, typedListener);
    addListener (SWT.DefaultSelection, typedListener);
}

/**
 * Adds the listener to the collection of listeners who will
 * be notified when an item in the receiver is expanded or collapsed
 * by sending it one of the messages defined in the <code>TreeListener</code>
 * interface.
 *
 * @param listener the listener which should be notified
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see TreeListener
 * @see #removeTreeListener
 */
public void addTreeListener(TreeListener listener) {
    checkWidget ();
    if (listener is null) error (SWT.ERROR_NULL_ARGUMENT);
    TypedListener typedListener = new TypedListener (listener);
    addListener (SWT.Expand, typedListener);
    addListener (SWT.Collapse, typedListener);
}

int calculateWidth (GtkTreeViewColumn *column, GtkTreeIter* iter, bool recurse) {
    OS.gtk_tree_view_column_cell_set_cell_data (column, modelHandle, iter, false, false);
    /*
    * Bug in GTK.  The width calculated by gtk_tree_view_column_cell_get_size()
    * always grows in size regardless of the text or images in the table.
    * The fix is to determine the column width from the cell renderers.
    */
    // Code intentionally commented
    //int [] width = new int [1];
    //OS.gtk_tree_view_column_cell_get_size (column, null, null, null, width, null);
    //return width [0];

    int width = 0;
    int w;
    GtkTreePath* path = null;

    if (OS.gtk_tree_view_get_expander_column (handle) is column) {
        /* indent */
        GdkRectangle rect;
        OS.gtk_widget_realize (handle);
        path = OS.gtk_tree_model_get_path (modelHandle, iter);
        OS.gtk_tree_view_get_cell_area (handle, path, column, &rect);
        width += rect.x;
        /* expander */
        OS.gtk_widget_style_get1 (handle, OS.expander_size.ptr, &w);
        width += w  + TreeItem.EXPANDER_EXTRA_PADDING;
    }
    OS.gtk_widget_style_get1(handle, OS.focus_line_width.ptr, &w);
    width += 2 * w ;
    auto list = OS.gtk_tree_view_column_get_cell_renderers (column);
    if (list is null) return 0;
    auto temp = list;
    while (temp !is null) {
        auto renderer = OS.g_list_data (temp);
        if (renderer !is null) {
            OS.gtk_cell_renderer_get_size (renderer, handle, null, null, null, &w, null);
            width += w ;
        }
        temp = OS.g_list_next (temp);
    }
    OS.g_list_free (list);

    if (recurse) {
        if (path is null) path = OS.gtk_tree_model_get_path (modelHandle, iter);
        bool expanded = OS.gtk_tree_view_row_expanded (handle, path) !is 0;
        if (expanded) {
            GtkTreeIter childIter;
            bool valid = OS.gtk_tree_model_iter_children (modelHandle, &childIter, iter) !is 0;
            while (valid) {
                width = Math.max (width, calculateWidth (column, &childIter, true));
                valid = OS.gtk_tree_model_iter_next (modelHandle, &childIter) !is 0;
            }
        }
    }

    if (path !is null) OS.gtk_tree_path_free (path);
    return width;
}

/**
 * Clears the item at the given zero-relative index in the receiver.
 * The text, icon and other attributes of the item are set to the default
 * value.  If the tree was created with the <code>SWT.VIRTUAL</code> style,
 * these attributes are requested again as needed.
 *
 * @param index the index of the item to clear
 * @param all <code>true</code> if all child items of the indexed item should be
 * cleared recursively, and <code>false</code> otherwise
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_INVALID_RANGE - if the index is not between 0 and the number of elements in the list minus 1 (inclusive)</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see SWT#VIRTUAL
 * @see SWT#SetData
 *
 * @since 3.2
 */
public void clear(int index, bool all) {
    checkWidget ();
    clear (null, index, all);
}

void clear (GtkTreeIter* parentIter, int index, bool all) {
    GtkTreeIter iter;
    OS.gtk_tree_model_iter_nth_child(modelHandle, &iter, parentIter, index);
    int value;
    OS.gtk_tree_model_get1 (modelHandle, &iter, ID_COLUMN, cast(void**)&value);
    if (value  !is -1) {
        TreeItem item = items [value ];
        item.clear ();
    }
    if (all) clearAll (all, &iter);
}

/**
 * Clears all the items in the receiver. The text, icon and other
 * attributes of the items are set to their default values. If the
 * tree was created with the <code>SWT.VIRTUAL</code> style, these
 * attributes are requested again as needed.
 *
 * @param all <code>true</code> if all child items should be cleared
 * recursively, and <code>false</code> otherwise
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see SWT#VIRTUAL
 * @see SWT#SetData
 *
 * @since 3.2
 */
public void clearAll (bool all) {
    checkWidget ();
    clearAll (all, null);
}
void clearAll (bool all, GtkTreeIter* parentIter) {
    int length = OS.gtk_tree_model_iter_n_children (modelHandle, parentIter);
    if (length is 0) return;
    GtkTreeIter iter;
    bool valid = cast(bool)OS.gtk_tree_model_iter_children (modelHandle, &iter, parentIter);
    int value;
    while (valid) {
        OS.gtk_tree_model_get1 (modelHandle, &iter, ID_COLUMN, cast(void**)&value);
        if (value  !is -1) {
            TreeItem item = items [value ];
            item.clear ();
        }
        if (all) clearAll (all, &iter);
        valid = cast(bool)OS.gtk_tree_model_iter_next (modelHandle, &iter);
    }
}

public override Point computeSize (int wHint, int hHint, bool changed) {
    checkWidget ();
    if (wHint !is SWT.DEFAULT && wHint < 0) wHint = 0;
    if (hHint !is SWT.DEFAULT && hHint < 0) hHint = 0;
    Point size = computeNativeSize (handle, wHint, hHint, changed);
    Rectangle trim = computeTrim (0, 0, size.x, size.y);
    size.x = trim.width;
    size.y = trim.height;
    return size;
}

void copyModel (void* oldModel, int oldStart, void* newModel, int newStart, size_t [] types, void* oldParent, void* newParent, int modelLength) {
    GtkTreeIter iter;
    if (OS.gtk_tree_model_iter_children (oldModel, &iter, oldParent))  {
        GtkTreeIter*[] oldItems = new GtkTreeIter*[]( OS.gtk_tree_model_iter_n_children (oldModel, oldParent));
        int oldIndex = 0;
        do {
            GtkTreeIter* newItem = cast(GtkTreeIter*)OS.g_malloc (GtkTreeIter.sizeof);
            if (newItem is null) error (SWT.ERROR_NO_HANDLES);
            OS.gtk_tree_store_append (newModel, newItem, newParent);
            int index;
            OS.gtk_tree_model_get1 (oldModel, &iter, ID_COLUMN, cast(void**)&index);
            TreeItem item = null;
            if (index  !is -1) {
                item = items [index ];
                if (item !is null) {
                    auto oldItem = cast(GtkTreeIter*)item.handle;
                    oldItems[oldIndex++] = oldItem;
                    void* ptr;
                    for (int j = 0; j < FIRST_COLUMN; j++) {
                        OS.gtk_tree_model_get1 (oldModel, oldItem, j, &ptr);
                        OS.gtk_tree_store_set1 (newModel, newItem, j, ptr );
                        if (types [j] is OS.G_TYPE_STRING ()) OS.g_free ((ptr ));
                    }
                    for (int j= 0; j<modelLength - FIRST_COLUMN; j++) {
                        OS.gtk_tree_model_get1 (oldModel, oldItem, oldStart + j, &ptr);
                        OS.gtk_tree_store_set1 (newModel, newItem, newStart + j, ptr );
                        if (types [j] is OS.G_TYPE_STRING ()) OS.g_free ((ptr ));
                    }
                }
            } else {
                OS.gtk_tree_store_set1 (newModel, newItem, ID_COLUMN, cast(void*)-1 );
            }
            // recurse through children
            copyModel(oldModel, oldStart, newModel, newStart, types, &iter, newItem, modelLength);

            if (item!is null) {
                item.handle = cast(GtkWidget*)newItem;
            } else {
                OS.g_free (newItem);
            }
        } while (OS.gtk_tree_model_iter_next(oldModel, &iter));
        for (int i = 0; i < oldItems.length; i++) {
            auto oldItem = oldItems [i];
            if (oldItem !is null) {
                OS.gtk_tree_store_remove (oldModel, oldItem);
                OS.g_free (oldItem);
            }
        }
    }
}

void createColumn (TreeColumn column, int index) {
/*
* Bug in ATK. For some reason, ATK segments fault if
* the GtkTreeView has a column and does not have items.
* The fix is to insert the column only when an item is
* created.
*/

    int modelIndex = FIRST_COLUMN;
    if (columnCount !is 0) {
        int modelLength = OS.gtk_tree_model_get_n_columns (modelHandle);
        bool [] usedColumns = new bool [modelLength];
        for (int i=0; i<columnCount; i++) {
            int columnIndex = columns [i].modelIndex;
            for (int j = 0; j < CELL_TYPES; j++) {
                usedColumns [columnIndex + j] = true;
            }
        }
        while (modelIndex < modelLength) {
            if (!usedColumns [modelIndex]) break;
            modelIndex++;
        }
        if (modelIndex is modelLength) {
            auto oldModel = modelHandle;
            size_t[] types = getColumnTypes (columnCount + 4); // grow by 4 rows at a time
            auto newModel = OS.gtk_tree_store_newv (cast(int)/*64bit*/types.length, types.ptr);
            if (newModel is null) error (SWT.ERROR_NO_HANDLES);
            copyModel (oldModel, FIRST_COLUMN, newModel, FIRST_COLUMN, types, null, null, modelLength);
            OS.gtk_tree_view_set_model (handle, newModel);
            OS.g_object_unref (oldModel);
            modelHandle = newModel;
        }
    }
    auto columnHandle = OS.gtk_tree_view_column_new ();
    if (columnHandle is null) error (SWT.ERROR_NO_HANDLES);
    if (index is 0 && columnCount > 0) {
        TreeColumn checkColumn = columns [0];
        createRenderers (cast(GtkTreeViewColumn *)checkColumn.handle, checkColumn.modelIndex, false, checkColumn.style);
    }
    createRenderers (columnHandle, modelIndex, index is 0, column is null ? 0 : column.style);
    /*
    * Use GTK_TREE_VIEW_COLUMN_GROW_ONLY on GTK versions < 2.3.2
    * because fixed_height_mode is not supported.
    */
    bool useVirtual = (style & SWT.VIRTUAL) !is 0 && OS.GTK_VERSION >= OS.buildVERSION (2, 3, 2);
    if (!useVirtual && columnCount is 0) {
        OS.gtk_tree_view_column_set_sizing (columnHandle, OS.GTK_TREE_VIEW_COLUMN_GROW_ONLY);
    } else {
        OS.gtk_tree_view_column_set_sizing (columnHandle, OS.GTK_TREE_VIEW_COLUMN_FIXED);
        if (columnCount !is 0) OS.gtk_tree_view_column_set_visible (columnHandle, false);
    }
    OS.gtk_tree_view_column_set_resizable (columnHandle, true);
    OS.gtk_tree_view_column_set_clickable (columnHandle, true);
    OS.gtk_tree_view_column_set_min_width (columnHandle, 0);
    OS.gtk_tree_view_insert_column (handle, columnHandle, index);
    if (column !is null) {
        column.handle = cast(GtkWidget*)columnHandle;
        column.modelIndex = modelIndex;
    }
    /* Disable searching when using VIRTUAL */
    if ((style & SWT.VIRTUAL) !is 0) {
        /*
        * Bug in GTK. Until GTK 2.6.5, calling gtk_tree_view_set_enable_search(FALSE)
        * would prevent the user from being able to type in text to search the tree.
        * After 2.6.5, GTK introduced Ctrl+F as being the key binding for interactive
        * search. This meant that even if FALSE was passed to enable_search, the user
        * can still bring up the search pop up using the keybinding. GTK also introduced
        * the notion of passing a -1 to gtk_set_search_column to disable searching
        * (including the search key binding).  The fix is to use the right calls
        * for the right version.
        */
        if (OS.GTK_VERSION >= OS.buildVERSION (2, 6, 5)) {
            OS.gtk_tree_view_set_search_column (handle, -1);
        } else {
            OS.gtk_tree_view_set_enable_search (handle, false);
        }
    } else {
        /* Set the search column whenever the model changes */
        int firstColumn = columnCount is 0 ? FIRST_COLUMN : columns [0].modelIndex;
        OS.gtk_tree_view_set_search_column (handle, firstColumn + CELL_TEXT);
    }
}

override void createHandle (int index) {
    state |= HANDLE;
    fixedHandle = cast(GtkWidget*)OS.g_object_new (display.gtk_fixed_get_type (), null);
    if (fixedHandle is null) error (SWT.ERROR_NO_HANDLES);
    OS.gtk_fixed_set_has_window (fixedHandle, true);
    scrolledHandle = cast(GtkWidget*)OS.gtk_scrolled_window_new (null, null);
    if (scrolledHandle is null) error (SWT.ERROR_NO_HANDLES);
    size_t[] types = getColumnTypes (1);
    modelHandle = cast(GtkTreeStore*)OS.gtk_tree_store_newv (cast(int)/*64bit*/types.length, types.ptr);
    if (modelHandle is null) error (SWT.ERROR_NO_HANDLES);
    handle = cast(GtkWidget*)OS.gtk_tree_view_new_with_model (modelHandle);
    if (handle is null) error (SWT.ERROR_NO_HANDLES);
    if ((style & SWT.CHECK) !is 0) {
        checkRenderer = cast(GtkCellRenderer*)OS.gtk_cell_renderer_toggle_new ();
        if (checkRenderer is null) error (SWT.ERROR_NO_HANDLES);
        OS.g_object_ref (checkRenderer);
    }
    createColumn (null, 0);
    OS.gtk_container_add (fixedHandle, scrolledHandle);
    OS.gtk_container_add (scrolledHandle, handle);

    int mode = (style & SWT.MULTI) !is 0 ? OS.GTK_SELECTION_MULTIPLE : OS.GTK_SELECTION_BROWSE;
    auto selectionHandle = OS.gtk_tree_view_get_selection (handle);
    OS.gtk_tree_selection_set_mode (selectionHandle, mode);
    OS.gtk_tree_view_set_headers_visible (handle, false);
    int hsp = (style & SWT.H_SCROLL) !is 0 ? OS.GTK_POLICY_AUTOMATIC : OS.GTK_POLICY_NEVER;
    int vsp = (style & SWT.V_SCROLL) !is 0 ? OS.GTK_POLICY_AUTOMATIC : OS.GTK_POLICY_NEVER;
    OS.gtk_scrolled_window_set_policy (scrolledHandle, hsp, vsp);
    if ((style & SWT.BORDER) !is 0) OS.gtk_scrolled_window_set_shadow_type (scrolledHandle, OS.GTK_SHADOW_ETCHED_IN);
    /* Disable searching when using VIRTUAL */
    if ((style & SWT.VIRTUAL) !is 0) {
        /* The fixed_height_mode property only exists in GTK 2.3.2 and greater */
        if (OS.GTK_VERSION >= OS.buildVERSION (2, 3, 2)) {
            OS.g_object_set1 (handle, OS.fixed_height_mode.ptr, true);
        }
        /*
        * Bug in GTK. Until GTK 2.6.5, calling gtk_tree_view_set_enable_search(FALSE)
        * would prevent the user from being able to type in text to search the tree.
        * After 2.6.5, GTK introduced Ctrl+F as being the key binding for interactive
        * search. This meant that even if FALSE was passed to enable_search, the user
        * can still bring up the search pop up using the keybinding. GTK also introduced
        * the notion of passing a -1 to gtk_set_search_column to disable searching
        * (including the search key binding).  The fix is to use the right calls
        * for the right version.
        */
        if (OS.GTK_VERSION >= OS.buildVERSION (2, 6, 5)) {
            OS.gtk_tree_view_set_search_column (handle, -1);
        } else {
            OS.gtk_tree_view_set_enable_search (handle, false);
        }
    }
}

void createItem (TreeColumn column, int index) {
    if (!(0 <= index && index <= columnCount)) error (SWT.ERROR_INVALID_RANGE);
    if (index is 0) {
        // first column must be left aligned
        column.style &= ~(SWT.LEFT | SWT.RIGHT | SWT.CENTER);
        column.style |= SWT.LEFT;
    }
    if (columnCount is 0) {
        column.handle = cast(GtkWidget*)OS.gtk_tree_view_get_column (handle, 0);
        OS.gtk_tree_view_column_set_sizing (column.handle, OS.GTK_TREE_VIEW_COLUMN_FIXED);
        OS.gtk_tree_view_column_set_visible (column.handle, false);
        column.modelIndex = FIRST_COLUMN;
        createRenderers (cast(GtkTreeViewColumn *)column.handle, column.modelIndex, true, column.style);
        column.customDraw = firstCustomDraw;
        firstCustomDraw = false;
    } else {
        createColumn (column, index);
    }
    auto boxHandle = OS.gtk_hbox_new (false, 3);
    if (boxHandle is null) error (SWT.ERROR_NO_HANDLES);
    auto labelHandle = OS.gtk_label_new_with_mnemonic (null);
    if (labelHandle is null) error (SWT.ERROR_NO_HANDLES);
    auto imageHandle = OS.gtk_image_new ();
    if (imageHandle is null) error (SWT.ERROR_NO_HANDLES);
    OS.gtk_container_add (boxHandle, imageHandle);
    OS.gtk_container_add (boxHandle, labelHandle);
    OS.gtk_widget_show (boxHandle);
    OS.gtk_widget_show (labelHandle);
    column.labelHandle = labelHandle;
    column.imageHandle = imageHandle;
    OS.gtk_tree_view_column_set_widget (column.handle, boxHandle);
    auto widget = OS.gtk_widget_get_parent (boxHandle);
    while (widget !is handle) {
        if (OS.GTK_IS_BUTTON (widget)) {
            column.buttonHandle = widget;
            break;
        }
        widget = OS.gtk_widget_get_parent (widget);
    }
    if (columnCount is columns.length) {
        TreeColumn [] newColumns = new TreeColumn [columns.length + 4];
        System.arraycopy (columns, 0, newColumns, 0, columns.length);
        columns = newColumns;
    }
    System.arraycopy (columns, index, columns, index + 1, columnCount++ - index);
    columns [index] = column;
    if ((state & FONT) !is 0) {
        column.setFontDescription (getFontDescription ());
    }
    if (columnCount >= 1) {
        for (int i=0; i<items.length; i++) {
            TreeItem item = items [i];
            if (item !is null) {
                Font [] cellFont = item.cellFont;
                if (cellFont !is null) {
                    Font [] temp = new Font [columnCount];
                    System.arraycopy (cellFont, 0, temp, 0, index);
                    System.arraycopy (cellFont, index, temp, index+1, columnCount-index-1);
                    item.cellFont = temp;
                }
            }
        }
    }
}

void createItem (TreeItem item, GtkTreeIter* parentIter, int index) {
    int count = OS.gtk_tree_model_iter_n_children (modelHandle, parentIter);
    if (index is -1) index = count;
    if (!(0 <= index && index <= count)) error (SWT.ERROR_INVALID_RANGE);
    item.handle = cast(GtkWidget*)OS.g_malloc (GtkTreeIter.sizeof);
    if (item.handle is null) error(SWT.ERROR_NO_HANDLES);
    /*
    * Feature in GTK.  It is much faster to append to a tree store
    * than to insert at the end using gtk_tree_store_insert().
    */
    if (index is count) {
        OS.gtk_tree_store_append (modelHandle, item.handle, parentIter);
    } else {
        OS.gtk_tree_store_insert (modelHandle, item.handle, parentIter, index);
    }
    int id = getId (cast(GtkTreeIter*) item.handle, false);
    items [id] = item;
    modelChanged = true;
}

void createRenderers (GtkTreeViewColumn* columnHandle, int modelIndex, bool check, int columnStyle) {
    OS.gtk_tree_view_column_clear (columnHandle);
    if ((style & SWT.CHECK) !is 0 && check) {
        OS.gtk_tree_view_column_pack_start (columnHandle, checkRenderer, false);
        OS.gtk_tree_view_column_add_attribute (columnHandle, checkRenderer, OS.active.ptr, CHECKED_COLUMN);
        /*
        * Feature in GTK. The inconsistent property only exists in GTK 2.2.x.
        */
        if (OS.GTK_VERSION >= OS.buildVERSION (2, 2, 0)) {
            OS.gtk_tree_view_column_add_attribute (columnHandle, checkRenderer, OS.inconsistent.ptr, GRAYED_COLUMN);
        }
        /*
        * Bug in GTK. GTK renders the background on top of the checkbox.
        * This only happens in version 2.2.1 and earlier. The fix is not to set the background.
        */
        if (OS.GTK_VERSION > OS.buildVERSION (2, 2, 1)) {
            if (!ownerDraw) OS.gtk_tree_view_column_add_attribute (columnHandle, checkRenderer, OS.cell_background_gdk.ptr, BACKGROUND_COLUMN);
        }
        if (ownerDraw) {
            display.doCellDataProc( handle, cast(GtkTreeViewColumn*)columnHandle, cast(GtkCellRenderer*)checkRenderer );
            OS.g_object_set_qdata (cast(GObject*)checkRenderer, Display.SWT_OBJECT_INDEX1, columnHandle);
        }
    }
    auto pixbufRenderer = ownerDraw ? cast(GtkCellRenderer*)OS.g_object_new (display.gtk_cell_renderer_pixbuf_get_type (), null) : OS.gtk_cell_renderer_pixbuf_new ();
    if (pixbufRenderer is null) error (SWT.ERROR_NO_HANDLES);
    auto textRenderer = ownerDraw ? cast(GtkCellRenderer*)OS.g_object_new (display.gtk_cell_renderer_text_get_type (), null) : OS.gtk_cell_renderer_text_new ();
    if (textRenderer is null) error (SWT.ERROR_NO_HANDLES);

    if (ownerDraw) {
        OS.g_object_set_qdata (cast(GObject*)pixbufRenderer, Display.SWT_OBJECT_INDEX1, columnHandle);
        OS.g_object_set_qdata (cast(GObject*)textRenderer, Display.SWT_OBJECT_INDEX1, columnHandle);
    }

    /*
    * Feature in GTK.  When a tree view column contains only one activatable
    * cell renderer such as a toggle renderer, mouse clicks anywhere in a cell
    * activate that renderer. The workaround is to set a second  cell renderer
    * to be activatable.
    */
    if ((style & SWT.CHECK) !is 0 && check) {
        OS.g_object_set1 (pixbufRenderer, OS.mode.ptr, OS.GTK_CELL_RENDERER_MODE_ACTIVATABLE);
    }

    /* Set alignment */
    if ((columnStyle & SWT.RIGHT) !is 0) {
        OS.g_object_set1_float(textRenderer, OS.xalign.ptr, 1.0f);
        OS.gtk_tree_view_column_pack_end (columnHandle, textRenderer, true);
        OS.gtk_tree_view_column_pack_end (columnHandle, pixbufRenderer, false);
        OS.gtk_tree_view_column_set_alignment (columnHandle, 1f);
    } else if ((columnStyle & SWT.CENTER) !is 0) {
        OS.g_object_set1_float(textRenderer, OS.xalign.ptr, 0.5f);
        OS.gtk_tree_view_column_pack_start (columnHandle, pixbufRenderer, false);
        OS.gtk_tree_view_column_pack_end (columnHandle, textRenderer, true);
        OS.gtk_tree_view_column_set_alignment (columnHandle, 0.5f);
    } else {
        OS.gtk_tree_view_column_pack_start (columnHandle, pixbufRenderer, false);
        OS.gtk_tree_view_column_pack_start (columnHandle, textRenderer, true);
        OS.gtk_tree_view_column_set_alignment (columnHandle, 0f);
    }

    /* Add attributes */
    OS.gtk_tree_view_column_add_attribute (columnHandle, pixbufRenderer, OS.pixbuf.ptr, modelIndex + CELL_PIXBUF);
    /*
     * Bug on GTK. Gtk renders the background on top of the pixbuf.
     * This only happens in version 2.2.1 and earlier. The fix is not to set the background.
     */
    if (OS.GTK_VERSION > OS.buildVERSION (2, 2, 1)) {
        if (!ownerDraw) {
            OS.gtk_tree_view_column_add_attribute (columnHandle, pixbufRenderer, OS.cell_background_gdk.ptr, BACKGROUND_COLUMN);
            OS.gtk_tree_view_column_add_attribute (columnHandle, textRenderer, OS.cell_background_gdk.ptr, BACKGROUND_COLUMN);
        }
    }
    OS.gtk_tree_view_column_add_attribute (columnHandle, textRenderer, OS.text.ptr, modelIndex + CELL_TEXT);
    OS.gtk_tree_view_column_add_attribute (columnHandle, textRenderer, OS.foreground_gdk.ptr, FOREGROUND_COLUMN);
    OS.gtk_tree_view_column_add_attribute (columnHandle, textRenderer, OS.font_desc.ptr, FONT_COLUMN);

    bool customDraw = firstCustomDraw;
    if (columnCount !is 0) {
        for (int i=0; i<columnCount; i++) {
            if (columns [i].handle is cast(GtkWidget*)columnHandle) {
                customDraw = columns [i].customDraw;
                break;
            }
        }
    }
    if ((style & SWT.VIRTUAL) !is 0 || customDraw || ownerDraw) {
        display.doCellDataProc( handle, cast(GtkTreeViewColumn*)columnHandle, cast(GtkCellRenderer*)textRenderer );
        display.doCellDataProc( handle, cast(GtkTreeViewColumn*)columnHandle, cast(GtkCellRenderer*)pixbufRenderer );
    }
}

override
void createWidget (int index) {
    super.createWidget (index);
    items = new TreeItem [4];
    columns = new TreeColumn [4];
    columnCount = 0;
}

GdkColor* defaultBackground () {
    return display.COLOR_LIST_BACKGROUND;
}

GdkColor* defaultForeground () {
    return display.COLOR_LIST_FOREGROUND;
}

override void deregister () {
    super.deregister ();
    display.removeWidget (cast(GtkWidget*)OS.gtk_tree_view_get_selection (handle));
    if (checkRenderer !is null) display.removeWidget (cast(GtkWidget*)checkRenderer);
}

/**
 * Deselects an item in the receiver.  If the item was already
 * deselected, it remains deselected.
 *
 * @param item the item to be deselected
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the item is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the item has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.4
 */
public void deselect (TreeItem item) {
    checkWidget ();
    if (item is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (item.isDisposed ()) error (SWT.ERROR_INVALID_ARGUMENT);
    bool fixColumn = showFirstColumn ();
    auto selection = OS.gtk_tree_view_get_selection (handle);
    OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    OS.gtk_tree_selection_unselect_iter (selection, item.handle);
    OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    if (fixColumn) hideFirstColumn ();
}

/**
 * Deselects all selected items in the receiver.
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void deselectAll() {
    checkWidget();
    bool fixColumn = showFirstColumn ();
    auto selection = OS.gtk_tree_view_get_selection (handle);
    OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    OS.gtk_tree_selection_unselect_all (selection);
    OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    if (fixColumn) hideFirstColumn ();
}

void destroyItem (TreeColumn column) {
    int index = 0;
    while (index < columnCount) {
        if (columns [index] is column) break;
        index++;
    }
    if (index is columnCount) return;
    auto columnHandle = column.handle;
    if (columnCount is 1) {
        firstCustomDraw = column.customDraw;
    }
    System.arraycopy (columns, index + 1, columns, index, --columnCount - index);
    columns [columnCount] = null;
    OS.gtk_tree_view_remove_column (handle, columnHandle);
    if (columnCount is 0) {
        auto oldModel = modelHandle;
        size_t[] types = getColumnTypes (1);
        auto newModel = OS.gtk_tree_store_newv (cast(int)/*64bit*/types.length, types.ptr);
        if (newModel is null) error (SWT.ERROR_NO_HANDLES);
        copyModel(oldModel, column.modelIndex, newModel, FIRST_COLUMN, types, null, null, FIRST_COLUMN + CELL_TYPES);
        OS.gtk_tree_view_set_model (handle, newModel);
        OS.g_object_unref (oldModel);
        modelHandle = newModel;
        createColumn (null, 0);

    } else {
        for (int i=0; i<items.length; i++) {
            TreeItem item = items [i];
            if (item !is null) {
                auto iter = cast(GtkTreeIter*)item.handle;
                int modelIndex = column.modelIndex;
                OS.gtk_tree_store_set1 (modelHandle, iter, modelIndex + CELL_PIXBUF, null);
                OS.gtk_tree_store_set1 (modelHandle, iter, modelIndex + CELL_TEXT, null);
                OS.gtk_tree_store_set1 (modelHandle, iter, modelIndex + CELL_FOREGROUND, null);
                OS.gtk_tree_store_set1 (modelHandle, iter, modelIndex + CELL_BACKGROUND, null);
                OS.gtk_tree_store_set1 (modelHandle, iter, modelIndex + CELL_FONT, null);

                Font [] cellFont = item.cellFont;
                if (cellFont !is null) {
                    if (columnCount is 0) {
                        item.cellFont = null;
                    } else {
                        Font [] temp = new Font [columnCount];
                        System.arraycopy (cellFont, 0, temp, 0, index);
                        System.arraycopy (cellFont, index + 1, temp, index, columnCount - index);
                        item.cellFont = temp;
                    }
                }
            }
        }
        if (index is 0) {
            // first column must be left aligned and must show check box
            TreeColumn firstColumn = columns [0];
            firstColumn.style &= ~(SWT.LEFT | SWT.RIGHT | SWT.CENTER);
            firstColumn.style |= SWT.LEFT;
            createRenderers (cast(GtkTreeViewColumn*)firstColumn.handle, firstColumn.modelIndex, true, firstColumn.style);
        }
    }
    /* Disable searching when using VIRTUAL */
    if ((style & SWT.VIRTUAL) !is 0) {
        /*
        * Bug in GTK. Until GTK 2.6.5, calling gtk_tree_view_set_enable_search(FALSE)
        * would prevent the user from being able to type in text to search the tree.
        * After 2.6.5, GTK introduced Ctrl+F as being the key binding for interactive
        * search. This meant that even if FALSE was passed to enable_search, the user
        * can still bring up the search pop up using the keybinding. GTK also introduced
        * the notion of passing a -1 to gtk_set_search_column to disable searching
        * (including the search key binding).  The fix is to use the right calls
        * for the right version.
        */
        if (OS.GTK_VERSION >= OS.buildVERSION (2, 6, 5)) {
            OS.gtk_tree_view_set_search_column (handle, -1);
        } else {
            OS.gtk_tree_view_set_enable_search (handle, false);
        }
    } else {
        /* Set the search column whenever the model changes */
        int firstColumn = columnCount is 0 ? FIRST_COLUMN : columns [0].modelIndex;
        OS.gtk_tree_view_set_search_column (handle, firstColumn + CELL_TEXT);
    }
}


void destroyItem (TreeItem item) {
    /*
    * Bug in GTK.  GTK segment faults when a root tree item
    * is destroyed when the tree is expanded and the last leaf of
    * the root is selected.  This only happens in versions earlier
    * than 2.0.6.  The fix is to collapse the tree item being destroyed
    * when it is a root, before it is destroyed.
    */
    if (OS.GTK_VERSION < OS.buildVERSION (2, 0, 6)) {
        int length = OS.gtk_tree_model_iter_n_children (modelHandle, null);
        if (length > 0) {
            GtkTreeIter iter;
            bool valid = cast(bool)OS.gtk_tree_model_iter_children (modelHandle, &iter, null);
            while (valid) {
                //PORTING_TODO: is this condition reasonable?
                if (item.handle is cast(GtkWidget*)&iter) {
                    item.setExpanded (false);
                    break;
                }
                valid = cast(bool)OS.gtk_tree_model_iter_next (modelHandle, &iter);
            }
        }
    }
    auto selection = OS.gtk_tree_view_get_selection (handle);
    OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    OS.gtk_tree_store_remove (modelHandle, item.handle);
    OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    modelChanged = true;
}

override bool dragDetect (int x, int y, bool filter, bool * consume) {
    bool selected = false;
    if (filter) {
        void* path;
        if (OS.gtk_tree_view_get_path_at_pos (handle, x, y, &path, null, null, null)) {
            if (path  !is null) {
                auto selection = OS.gtk_tree_view_get_selection (handle);
                if (OS.gtk_tree_selection_path_is_selected (selection, path )) selected = true;
                OS.gtk_tree_path_free (path );
            }
        } else {
            return false;
        }
    }
    bool dragDetect = super.dragDetect (x, y, filter, consume);
    if (dragDetect && selected && consume !is null) consume [0] = true;
    return dragDetect;
}

override GdkDrawable* eventWindow () {
    return paintWindow ();
}

override void fixChildren (Shell newShell, Shell oldShell, Decorations newDecorations, Decorations oldDecorations, Menu [] menus) {
    super.fixChildren (newShell, oldShell, newDecorations, oldDecorations, menus);
    for (int i=0; i<columnCount; i++) {
        TreeColumn column = columns [i];
        if (column.toolTipText !is null) {
            column.setToolTipText(oldShell, null);
            column.setToolTipText(newShell, column.toolTipText);
        }
    }
}

override GdkColor* getBackgroundColor () {
    return getBaseColor ();
}

public override Rectangle getClientArea () {
    checkWidget ();
    forceResize ();
    OS.gtk_widget_realize (handle);
    auto fixedWindow = OS.GTK_WIDGET_WINDOW (fixedHandle);
    auto binWindow = OS.gtk_tree_view_get_bin_window (handle);
    int binX, binY;
    OS.gdk_window_get_origin (binWindow, &binX, &binY);
    int fixedX, fixedY;
    OS.gdk_window_get_origin (fixedWindow, &fixedX, &fixedY);
    auto clientHandle = clientHandle ();
    int width = (state & ZERO_WIDTH) !is 0 ? 0 : OS.GTK_WIDGET_WIDTH (clientHandle);
    int height = (state & ZERO_HEIGHT) !is 0 ? 0 : OS.GTK_WIDGET_HEIGHT (clientHandle);
    return new Rectangle (fixedX  - binX , fixedY  - binY , width, height);
}

override
int getClientWidth () {
    int w, h;
    OS.gtk_widget_realize (handle);
    OS.gdk_drawable_get_size(OS.gtk_tree_view_get_bin_window(handle), &w, &h);
    return w;
}

/**
 * Returns the column at the given, zero-relative index in the
 * receiver. Throws an exception if the index is out of range.
 * Columns are returned in the order that they were created.
 * If no <code>TreeColumn</code>s were created by the programmer,
 * this method will throw <code>ERROR_INVALID_RANGE</code> despite
 * the fact that a single column of data may be visible in the tree.
 * This occurs when the programmer uses the tree like a list, adding
 * items but never creating a column.
 *
 * @param index the index of the column to return
 * @return the column at the given index
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_INVALID_RANGE - if the index is not between 0 and the number of elements in the list minus 1 (inclusive)</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see Tree#getColumnOrder()
 * @see Tree#setColumnOrder(int[])
 * @see TreeColumn#getMoveable()
 * @see TreeColumn#setMoveable(bool)
 * @see SWT#Move
 *
 * @since 3.1
 */
public TreeColumn getColumn (int index) {
    checkWidget();
    if (!(0 <= index && index < columnCount)) error (SWT.ERROR_INVALID_RANGE);
    return columns [index];
}

/**
 * Returns the number of columns contained in the receiver.
 * If no <code>TreeColumn</code>s were created by the programmer,
 * this value is zero, despite the fact that visually, one column
 * of items may be visible. This occurs when the programmer uses
 * the tree like a list, adding items but never creating a column.
 *
 * @return the number of columns
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public int getColumnCount () {
    checkWidget();
    return columnCount;
}

/**
 * Returns an array of zero-relative integers that map
 * the creation order of the receiver's items to the
 * order in which they are currently being displayed.
 * <p>
 * Specifically, the indices of the returned array represent
 * the current visual order of the items, and the contents
 * of the array represent the creation order of the items.
 * </p><p>
 * Note: This is not the actual structure used by the receiver
 * to maintain its list of items, so modifying the array will
 * not affect the receiver.
 * </p>
 *
 * @return the current visual order of the receiver's items
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see Tree#setColumnOrder(int[])
 * @see TreeColumn#getMoveable()
 * @see TreeColumn#setMoveable(bool)
 * @see SWT#Move
 *
 * @since 3.2
 */
public int [] getColumnOrder () {
    checkWidget ();
    if (columnCount is 0) return null;
    auto list = OS.gtk_tree_view_get_columns (handle);
    if (list is null) return null;
    int  i = 0, count = OS.g_list_length (list);
    int [] order = new int [count];
    auto temp = list;
    while (temp !is null) {
        auto column = OS.g_list_data (temp);
        if (column !is null) {
            for (int j=0; j<columnCount; j++) {
                if (columns [j].handle is column) {
                    order [i++] = j;
                    break;
                }
            }
        }
        temp = OS.g_list_next (temp);
    }
    OS.g_list_free (list);
    return order;
}

size_t[] getColumnTypes (int columnCount) {
    size_t[] types = new size_t [FIRST_COLUMN + (columnCount * CELL_TYPES)];
    // per row data
    types [ID_COLUMN] = OS.G_TYPE_INT ();
    types [CHECKED_COLUMN] = OS.G_TYPE_BOOLEAN ();
    types [GRAYED_COLUMN] = OS.G_TYPE_BOOLEAN ();
    types [FOREGROUND_COLUMN] = OS.GDK_TYPE_COLOR ();
    types [BACKGROUND_COLUMN] = OS.GDK_TYPE_COLOR ();
    types [FONT_COLUMN] = OS.PANGO_TYPE_FONT_DESCRIPTION ();
    // per cell data
    for (int i=FIRST_COLUMN; i<types.length; i+=CELL_TYPES) {
        types [i + CELL_PIXBUF] = OS.GDK_TYPE_PIXBUF ();
        types [i + CELL_TEXT] = OS.G_TYPE_STRING ();
        types [i + CELL_FOREGROUND] = OS.GDK_TYPE_COLOR ();
        types [i + CELL_BACKGROUND] = OS.GDK_TYPE_COLOR ();
        types [i + CELL_FONT] = OS.PANGO_TYPE_FONT_DESCRIPTION ();
    }
    return types;
}

/**
 * Returns an array of <code>TreeColumn</code>s which are the
 * columns in the receiver. Columns are returned in the order
 * that they were created.  If no <code>TreeColumn</code>s were
 * created by the programmer, the array is empty, despite the fact
 * that visually, one column of items may be visible. This occurs
 * when the programmer uses the tree like a list, adding items but
 * never creating a column.
 * <p>
 * Note: This is not the actual structure used by the receiver
 * to maintain its list of items, so modifying the array will
 * not affect the receiver.
 * </p>
 *
 * @return the items in the receiver
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see Tree#getColumnOrder()
 * @see Tree#setColumnOrder(int[])
 * @see TreeColumn#getMoveable()
 * @see TreeColumn#setMoveable(bool)
 * @see SWT#Move
 *
 * @since 3.1
 */
public TreeColumn [] getColumns () {
    checkWidget();
    TreeColumn [] result = new TreeColumn [columnCount];
    System.arraycopy (columns, 0, result, 0, columnCount);
    return result;
}

TreeItem getFocusItem () {
    GtkTreePath* path;
    OS.gtk_tree_view_get_cursor (handle, &path, null);
    if (path  is null) return null;
    TreeItem item = null;
    GtkTreeIter iter;
    if (OS.gtk_tree_model_get_iter (modelHandle, &iter, path)) {
        int index;
        OS.gtk_tree_model_get1 (modelHandle, &iter, ID_COLUMN, cast(void**)&index);
        if (index  !is -1) item = items [index ]; //TODO should we be creating this item when index is -1?
    }
    OS.gtk_tree_path_free (path );
    return item;
}

override GdkColor* getForegroundColor () {
    return getTextColor ();
}

/**
 * Returns the width in pixels of a grid line.
 *
 * @return the width of a grid line in pixels
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public int getGridLineWidth () {
    checkWidget();
    return 0;
}

/**
 * Returns the height of the receiver's header
 *
 * @return the height of the header or zero if the header is not visible
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public int getHeaderHeight () {
    checkWidget ();
    if (!OS.gtk_tree_view_get_headers_visible (handle)) return 0;
    if (columnCount > 0) {
        GtkRequisition requisition;
        int height = 0;
        for (int i=0; i<columnCount; i++) {
            auto buttonHandle = columns [i].buttonHandle;
            if (buttonHandle !is null) {
                OS.gtk_widget_size_request (buttonHandle, &requisition);
                height = Math.max (height, requisition.height);
            }
        }
        return height;
    }
    OS.gtk_widget_realize (handle);
    auto fixedWindow = OS.GTK_WIDGET_WINDOW (fixedHandle);
    auto binWindow = OS.gtk_tree_view_get_bin_window (handle);
    int binY ;
    OS.gdk_window_get_origin (binWindow, null, &binY);
    int fixedY;
    OS.gdk_window_get_origin (fixedWindow, null, &fixedY);
    return binY  - fixedY;
}

/**
 * Returns <code>true</code> if the receiver's header is visible,
 * and <code>false</code> otherwise.
 * <p>
 * If one of the receiver's ancestors is not visible or some
 * other condition makes the receiver not visible, this method
 * may still indicate that it is considered visible even though
 * it may not actually be showing.
 * </p>
 *
 * @return the receiver's header's visibility state
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public bool getHeaderVisible () {
    checkWidget();
    return cast(bool)OS.gtk_tree_view_get_headers_visible (handle);
}

/**
 * Returns the item at the given, zero-relative index in the
 * receiver. Throws an exception if the index is out of range.
 *
 * @param index the index of the item to return
 * @return the item at the given index
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_INVALID_RANGE - if the index is not between 0 and the number of elements in the list minus 1 (inclusive)</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public TreeItem getItem (int index) {
    checkWidget();
    if (!(0 <= index && index < OS.gtk_tree_model_iter_n_children (modelHandle, null)))  {
        error (SWT.ERROR_INVALID_RANGE);
    }
    return _getItem (null, index);
}

/**
 * Returns the item at the given point in the receiver
 * or null if no such item exists. The point is in the
 * coordinate system of the receiver.
 * <p>
 * The item that is returned represents an item that could be selected by the user.
 * For example, if selection only occurs in items in the first column, then null is
 * returned if the point is outside of the item.
 * Note that the SWT.FULL_SELECTION style hint, which specifies the selection policy,
 * determines the extent of the selection.
 * </p>
 *
 * @param point the point used to locate the item
 * @return the item at the given point, or null if the point is not in a selectable item
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the point is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public TreeItem getItem (Point point) {
    checkWidget ();
    if (point is null) error (SWT.ERROR_NULL_ARGUMENT);
    void* path;
    OS.gtk_widget_realize (handle);
    GtkTreeViewColumn* columnHandle;
    if (!OS.gtk_tree_view_get_path_at_pos (handle, point.x, point.y, &path, &columnHandle, null, null)) return null;
    if (path  is null) return null;
    TreeItem item = null;
    GtkTreeIter iter;
    if (OS.gtk_tree_model_get_iter (modelHandle, &iter, path )) {
        bool overExpander = false;
        if (OS.gtk_tree_view_get_expander_column (handle) is columnHandle ) {
            int buffer;
            GdkRectangle rect;
            OS.gtk_tree_view_get_cell_area (handle, path, columnHandle, &rect);
            if (OS.GTK_VERSION < OS.buildVERSION (2, 8, 18)) {
                OS.gtk_widget_style_get1 (handle, OS.expander_size.ptr, &buffer);
                int expanderSize = buffer  + TreeItem.EXPANDER_EXTRA_PADDING;
                overExpander = point.x < rect.x + expanderSize;
            } else {
                overExpander = point.x < rect.x;
            }
        }
        if (!overExpander) {
            item = _getItem (&iter);
        }
    }
    OS.gtk_tree_path_free (path );
    return item;
}

/**
 * Returns the number of items contained in the receiver
 * that are direct item children of the receiver.  The
 * number that is returned is the number of roots in the
 * tree.
 *
 * @return the number of items
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public int getItemCount () {
    checkWidget ();
    return OS.gtk_tree_model_iter_n_children (modelHandle, null);
}

/**
 * Returns the height of the area which would be used to
 * display <em>one</em> of the items in the tree.
 *
 * @return the height of one item
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public int getItemHeight () {
    checkWidget ();
    int itemCount = OS.gtk_tree_model_iter_n_children (modelHandle, null);
    if (itemCount is 0) {
        auto column = OS.gtk_tree_view_get_column (handle, 0);
        int w, h;
        ignoreSize = true;
        OS.gtk_tree_view_column_cell_get_size (column, null, null, null, &w, &h);
        ignoreSize = false;
        return h ;
    } else {
        int height = 0;
        GtkTreeIter iter;
        OS.gtk_tree_model_get_iter_first (modelHandle, &iter);
        int columnCount = Math.max (1, this.columnCount);
        for (int i=0; i<columnCount; i++) {
            auto column = OS.gtk_tree_view_get_column (handle, i);
            OS.gtk_tree_view_column_cell_set_cell_data (column, modelHandle, &iter, false, false);
            int w, h;
            OS.gtk_tree_view_column_cell_get_size (column, null, null, null, &w, &h);
            height = Math.max (height, h );
        }
        return height;
    }
}

/**
 * Returns a (possibly empty) array of items contained in the
 * receiver that are direct item children of the receiver.  These
 * are the roots of the tree.
 * <p>
 * Note: This is not the actual structure used by the receiver
 * to maintain its list of items, so modifying the array will
 * not affect the receiver.
 * </p>
 *
 * @return the items
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public TreeItem [] getItems () {
    checkWidget();
    return getItems (null);
}

TreeItem [] getItems (GtkTreeIter* parent) {
    int length = OS.gtk_tree_model_iter_n_children (modelHandle, parent);
    TreeItem[] result = new TreeItem [length];
    if (length is 0) return result;
    if ((style & SWT.VIRTUAL) !is 0) {
        for (int i=0; i<length; i++) {
            result [i] = _getItem (parent, i);
        }
    } else {
        int i = 0;
        int index;
        GtkTreeIter iter;
        bool valid = cast(bool)OS.gtk_tree_model_iter_children (modelHandle, &iter, parent);
        while (valid) {
            OS.gtk_tree_model_get1 (modelHandle, &iter, ID_COLUMN, cast(void**)&index);
            result [i++] = items [index ];
            valid = cast(bool)OS.gtk_tree_model_iter_next (modelHandle, &iter);
        }
    }
    return result;
}

/**
 * Returns <code>true</code> if the receiver's lines are visible,
 * and <code>false</code> otherwise.
 * <p>
 * If one of the receiver's ancestors is not visible or some
 * other condition makes the receiver not visible, this method
 * may still indicate that it is considered visible even though
 * it may not actually be showing.
 * </p>
 *
 * @return the visibility state of the lines
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public bool getLinesVisible() {
    checkWidget();
    return cast(bool)OS.gtk_tree_view_get_rules_hint (handle);
}

/**
 * Returns the receiver's parent item, which must be a
 * <code>TreeItem</code> or null when the receiver is a
 * root.
 *
 * @return the receiver's parent item
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public TreeItem getParentItem () {
    checkWidget ();
    return null;
}

GtkCellRendererPixbuf* getPixbufRenderer (GtkTreeViewColumn* column) {
    auto list = OS.gtk_tree_view_column_get_cell_renderers (column);
    if (list is null) return null;
    int count = OS.g_list_length (list);
    GtkCellRendererPixbuf* pixbufRenderer;
    int i = 0;
    while (i < count) {
        auto renderer = OS.g_list_nth_data (list, i);
        if (OS.GTK_IS_CELL_RENDERER_PIXBUF (renderer)) {
            pixbufRenderer = cast(GtkCellRendererPixbuf*)renderer;
            break;
        }
        i++;
    }
    OS.g_list_free (list);
    return pixbufRenderer;
}

/**
 * Returns an array of <code>TreeItem</code>s that are currently
 * selected in the receiver. The order of the items is unspecified.
 * An empty array indicates that no items are selected.
 * <p>
 * Note: This is not the actual structure used by the receiver
 * to maintain its selection, so modifying the array will
 * not affect the receiver.
 * </p>
 * @return an array representing the selection
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public TreeItem[] getSelection () {
    checkWidget();
    auto selection = OS.gtk_tree_view_get_selection (handle);
    if (OS.GTK_VERSION < OS.buildVERSION (2, 2, 0)) {
        display.treeSelectionLength  = 0;
        display.treeSelection = new int [items.length];
        display.doTreeSelectionProcConnect( &treeSelectionCallbackData, handle, selection );
        TreeItem [] result = new TreeItem [display.treeSelectionLength];
        for (int i=0; i<result.length; i++) result [i] = items [display.treeSelection [i]];
        return result;
    }
    /*
    * Bug in GTK.  gtk_tree_selection_get_selected_rows() segmentation faults
    * in versions smaller than 2.2.4 if the model is NULL.  The fix is
    * to give a valid pointer instead.
    */
    int dummy;
    void* model = OS.GTK_VERSION < OS.buildVERSION (2, 2, 4) ? &dummy : null;
    auto list = OS.gtk_tree_selection_get_selected_rows (selection, &model);
    if (list !is null) {
        int count = OS.g_list_length (list);
        TreeItem [] treeSelection = new TreeItem [count];
        int length_ = 0;
        for (int i=0; i<count; i++) {
            auto data = OS.g_list_nth_data (list, i);
            GtkTreeIter iter;
            if (OS.gtk_tree_model_get_iter (modelHandle, &iter, data)) {
                treeSelection [length_] = _getItem (&iter);
                length_++;
            }
        }
        OS.g_list_free (list);
        if (length_ < count) {
            TreeItem [] temp = new TreeItem [length_];
            System.arraycopy(treeSelection, 0, temp, 0, length_);
            treeSelection = temp;
        }
        return treeSelection;
    }
    return null;
}

/**
 * Returns the number of selected items contained in the receiver.
 *
 * @return the number of selected items
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public int getSelectionCount () {
    checkWidget();
    auto selection = OS.gtk_tree_view_get_selection (handle);
    if (OS.GTK_VERSION < OS.buildVERSION (2, 2, 0)) {
        display.treeSelectionLength = 0;
        display.treeSelection = null;
        display.doTreeSelectionProcConnect( &treeSelectionCallbackData, handle, selection );
        return display.treeSelectionLength;
    }
    return OS.gtk_tree_selection_count_selected_rows (selection);
}

/**
 * Returns the column which shows the sort indicator for
 * the receiver. The value may be null if no column shows
 * the sort indicator.
 *
 * @return the sort indicator
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see #setSortColumn(TreeColumn)
 *
 * @since 3.2
 */
public TreeColumn getSortColumn () {
    checkWidget ();
    return sortColumn;
}

/**
 * Returns the direction of the sort indicator for the receiver.
 * The value will be one of <code>UP</code>, <code>DOWN</code>
 * or <code>NONE</code>.
 *
 * @return the sort direction
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see #setSortDirection(int)
 *
 * @since 3.2
 */
public int getSortDirection () {
    checkWidget ();
    return sortDirection;
}

GtkCellRendererText* getTextRenderer (GtkTreeViewColumn* column) {
    auto list = OS.gtk_tree_view_column_get_cell_renderers (column);
    if (list is null) return null;
    int count = OS.g_list_length (list);
    GtkCellRendererText* textRenderer;
    int i = 0;
    while (i < count) {
        auto renderer = OS.g_list_nth_data (list, i);
         if (OS.GTK_IS_CELL_RENDERER_TEXT (renderer)) {
            textRenderer = cast(GtkCellRendererText*)renderer;
            break;
        }
        i++;
    }
    OS.g_list_free (list);
    return textRenderer;
}

/**
 * Returns the item which is currently at the top of the receiver.
 * This item can change when items are expanded, collapsed, scrolled
 * or new items are added or removed.
 *
 * @return the item at the top of the receiver
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 2.1
 */
public TreeItem getTopItem () {
    checkWidget ();
    void* path;
    OS.gtk_widget_realize (handle);
    if (!OS.gtk_tree_view_get_path_at_pos (handle, 1, 1, &path, null, null, null)) return null;
    if (path  is null) return null;
    TreeItem item = null;
    GtkTreeIter iter;
    if (OS.gtk_tree_model_get_iter (modelHandle, &iter, path )) {
        item = _getItem (&iter);
    }
    OS.gtk_tree_path_free (path );
    return item;
}

override int gtk_button_press_event (GtkWidget* widget, GdkEventButton* gdkEvent) {
    if (gdkEvent.window !is OS.gtk_tree_view_get_bin_window (handle)) return 0;
    auto result = super.gtk_button_press_event (widget, gdkEvent);
    if (result !is 0) return result;
    /*
    * Feature in GTK.  In a multi-select tree view, when multiple items are already
    * selected, the selection state of the item is toggled and the previous selection
    * is cleared. This is not the desired behaviour when bringing up a popup menu.
    * Also, when an item is reselected with the right button, the tree view issues
    * an unwanted selection event. The workaround is to detect that case and not
    * run the default handler when the item is already part of the current selection.
    */
    int button = gdkEvent.button;
    if (button is 3 && gdkEvent.type is OS.GDK_BUTTON_PRESS) {
        void* path;
        if (OS.gtk_tree_view_get_path_at_pos (handle, cast(int)/*64bit*/gdkEvent.x, cast(int)/*64bit*/gdkEvent.y, &path, null, null, null)) {
            if (path !is null) {
                auto selection = OS.gtk_tree_view_get_selection (handle);
                if (OS.gtk_tree_selection_path_is_selected (selection, path )) result = 1;
                OS.gtk_tree_path_free (path );
            }
        }
    }

    /*
    * Feature in GTK.  When the user clicks in a single selection GtkTreeView
    * and there are no selected items, the first item is selected automatically
    * before the click is processed, causing two selection events.  The is fix
    * is the set the cursor item to be same as the clicked item to stop the
    * widget from automatically selecting the first item.
    */
    if ((style & SWT.SINGLE) !is 0 && getSelectionCount () is 0) {
        void* path;
        if (OS.gtk_tree_view_get_path_at_pos (handle, cast(int)/*64bit*/gdkEvent.x, cast(int)/*64bit*/gdkEvent.y, &path, null, null, null)) {
            if (path  !is null) {
                auto selection = OS.gtk_tree_view_get_selection (handle);
                OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
                OS.gtk_tree_view_set_cursor (handle, path , null, false);
                OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
                OS.gtk_tree_path_free (path );
            }
        }
    }
    /*
    * Bug in GTK. GTK segments fault, if the GtkTreeView widget is
    * not in focus and all items in the widget are disposed before
    * it finishes processing a button press.  The fix is to give
    * focus to the widget before it starts processing the event.
    */
    if (!OS.GTK_WIDGET_HAS_FOCUS (handle)) {
        OS.gtk_widget_grab_focus (handle);
    }
    return result;
}

override int gtk_button_release_event (GtkWidget* widget, GdkEventButton* event) {
    auto window = OS.GDK_EVENT_WINDOW (event);
    if (window !is OS.gtk_tree_view_get_bin_window (handle)) return 0;
    return super.gtk_button_release_event (widget, event);
}

override int gtk_changed (GtkWidget* widget) {
    TreeItem item = getFocusItem ();
    if (item !is null) {
        Event event = new Event ();
        event.item = item;
        postEvent (SWT.Selection, event);
    }
    return 0;
}

override int gtk_expand_collapse_cursor_row (GtkWidget* widget, ptrdiff_t logical, ptrdiff_t expand, ptrdiff_t open_all) {
    // FIXME - this flag is never cleared.  It should be cleared when the expand all operation completes.
    if (expand !is 0 && open_all !is 0) expandAll = true;
    return 0;
}

override int gtk_key_press_event (GtkWidget* widget, GdkEventKey* keyEvent) {
    auto result = super.gtk_key_press_event (widget, keyEvent);
    if (result !is 0) return result;
    if (OS.GTK_VERSION < OS.buildVERSION (2, 2 ,0)) {
        /*
        * Feature in GTK 2.0.x.  When an item is default selected using
        * the return key, GTK does not issue notification. The fix is
        * to issue this notification when the return key is pressed.
        */
        int key = keyEvent.keyval;
        switch (key) {
            case OS.GDK_Return:
            case OS.GDK_KP_Enter: {
                Event event = new Event ();
                event.item = getFocusItem ();
                postEvent (SWT.DefaultSelection, event);
                break;
            }
            default:
        }
    }
    return result;
}

override int gtk_motion_notify_event (GtkWidget* widget, GdkEventMotion* event) {
    auto window = OS.GDK_EVENT_WINDOW (event);
    if (window !is OS.gtk_tree_view_get_bin_window (handle)) return 0;
    return super.gtk_motion_notify_event (widget, event);
}

override int gtk_popup_menu (GtkWidget* widget) {
    auto result = super.gtk_popup_menu (widget);
    /*
    * Bug in GTK.  The context menu for the typeahead in GtkTreeViewer
    * opens in the bottom right corner of the screen when Shift+F10
    * is pressed and the typeahead window was not visible.  The fix is
    * to prevent the context menu from opening by stopping the default
    * handler.
    *
    * NOTE: The bug only happens in GTK 2.6.5 and lower.
    */
    return OS.GTK_VERSION < OS.buildVERSION (2, 6, 5) ? 1 : result;
}

override void gtk_row_activated (GtkTreeView* tree, GtkTreePath* path, GtkTreeViewColumn* column) {
    if (path is null) return;
    TreeItem item = null;
    GtkTreeIter iter;
    if (OS.gtk_tree_model_get_iter (modelHandle, &iter, path)) {
        int index;
        OS.gtk_tree_model_get1 (modelHandle, &iter, ID_COLUMN, cast(void**)&index);
        item = items [index ];
    }
    Event event = new Event ();
    event.item = item;
    postEvent (SWT.DefaultSelection, event);
    return;
}

override int gtk_test_collapse_row (
    GtkTreeView *tree,
    GtkTreeIter *iter,
    GtkTreePath *path)
{
    int index ;
    OS.gtk_tree_model_get1 (modelHandle, iter, ID_COLUMN, cast(void**)&index);
    TreeItem item = items [index ];
    Event event = new Event ();
    event.item = item;
    bool oldModelChanged = modelChanged;
    modelChanged = false;
    sendEvent (SWT.Collapse, event);
    /*
    * Bug in GTK.  Collapsing the target row during the test_collapse_row
    * handler will cause a segmentation fault if the animation code is allowed
    * to run.  The fix is to block the animation if the row is already
    * collapsed.
    */
    bool changed = modelChanged || !OS.gtk_tree_view_row_expanded (handle, path);
    modelChanged = oldModelChanged;
    if (isDisposed () || item.isDisposed ()) return 1;
    /*
    * Bug in GTK.  Expanding or collapsing a row which has no more
    * children causes the model state to become invalid, causing
    * GTK to give warnings and behave strangely.  Other changes to
    * the model can cause expansion to fail when using the multiple
    * expansion keys (such as *).  The fix is to stop the expansion
    * if there are model changes.
    *
    * Note: This callback must return 0 for the collapsing
    * animation to occur.
    */
    if (changed) {
        OS.g_signal_handlers_block_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udTEST_COLLAPSE_ROW);
        OS.gtk_tree_view_collapse_row (handle, path);
        OS.g_signal_handlers_unblock_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udTEST_COLLAPSE_ROW);
        return 1;
    }
    return 0;
}

override int gtk_test_expand_row (
    GtkTreeView *tree,
    GtkTreeIter *iter,
    GtkTreePath *path)
{
    int index ;
    OS.gtk_tree_model_get1 (modelHandle, iter, ID_COLUMN, cast(void**)&index);
    TreeItem item = items [index ];
    Event event = new Event ();
    event.item = item;
    bool oldModelChanged = modelChanged;
    modelChanged = false;
    sendEvent (SWT.Expand, event);
    /*
    * Bug in GTK.  Expanding the target row during the test_expand_row
    * handler will cause a segmentation fault if the animation code is allowed
    * to run.  The fix is to block the animation if the row is already
    * expanded.
    */
    bool changed = modelChanged || OS.gtk_tree_view_row_expanded (handle, path);
    modelChanged = oldModelChanged;
    if (isDisposed () || item.isDisposed ()) return 1;
    /*
    * Bug in GTK.  Expanding or collapsing a row which has no more
    * children causes the model state to become invalid, causing
    * GTK to give warnings and behave strangely.  Other changes to
    * the model can cause expansion to fail when using the multiple
    * expansion keys (such as *).  The fix is to stop the expansion
    * if there are model changes.
    *
    * Bug in GTK.  test-expand-row does not get called for each row
    * in an expand all operation.  The fix is to block the initial
    * expansion and only expand a single level.
    *
    * Note: This callback must return 0 for the collapsing
    * animation to occur.
    */
    if (changed || expandAll) {
        OS.g_signal_handlers_block_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udTEST_EXPAND_ROW);
        OS.gtk_tree_view_expand_row (handle, path, false);
        OS.g_signal_handlers_unblock_matched (handle, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udTEST_EXPAND_ROW);
        return 1;
    }
    return 0;
}

override int gtk_toggled (int renderer, char* pathStr) {
    auto path = OS.gtk_tree_path_new_from_string (pathStr);
    if (path is null) return 0;
    TreeItem item = null;
    GtkTreeIter iter;
    if (OS.gtk_tree_model_get_iter (modelHandle, &iter, path)) {
        item = _getItem (&iter);
    }
    OS.gtk_tree_path_free (path);
    if (item !is null) {
        item.setChecked (!item.getChecked ());
        Event event = new Event ();
        event.detail = SWT.CHECK;
        event.item = item;
        postEvent (SWT.Selection, event);
    }
    return 0;
}

override void gtk_widget_size_request (GtkWidget* widget, GtkRequisition* requisition) {
    /*
     * Bug in GTK.  For some reason, gtk_widget_size_request() fails
     * to include the height of the tree view items when there are
     * no columns visible.  The fix is to temporarily make one column
     * visible.
     */
    if (columnCount is 0) {
        super.gtk_widget_size_request (widget, requisition);
        return;
    }
    auto columns = OS.gtk_tree_view_get_columns (handle), list = columns;
    bool fixVisible = columns !is null;
    while (list !is null) {
        auto column = OS.g_list_data (list);
        if (OS.gtk_tree_view_column_get_visible (column)) {
            fixVisible = false;
            break;
        }
        list = OS.g_list_next (list);
    }
    GtkTreeViewColumn* columnHandle;
    if (fixVisible) {
        columnHandle = cast(GtkTreeViewColumn*)OS.g_list_data (columns);
        OS.gtk_tree_view_column_set_visible (columnHandle, true);
    }
    super.gtk_widget_size_request (widget, requisition);
    if (fixVisible) {
        OS.gtk_tree_view_column_set_visible (columnHandle, false);
    }
    if (columns !is null) OS.g_list_free (columns);
}

void hideFirstColumn () {
    auto firstColumn = OS.gtk_tree_view_get_column (handle, 0);
    OS.gtk_tree_view_column_set_visible (firstColumn, false);
}

override void hookEvents () {
    super.hookEvents ();
    auto selection = OS.gtk_tree_view_get_selection(handle);
    OS.g_signal_connect_closure (selection, OS.changed.ptr, display.closures [CHANGED], false);
    OS.g_signal_connect_closure (handle, OS.row_activated.ptr, display.closures [ROW_ACTIVATED], false);
    OS.g_signal_connect_closure (handle, OS.test_expand_row.ptr, display.closures [TEST_EXPAND_ROW], false);
    OS.g_signal_connect_closure (handle, OS.test_collapse_row.ptr, display.closures [TEST_COLLAPSE_ROW], false);
    OS.g_signal_connect_closure (handle, OS.expand_collapse_cursor_row.ptr, display.closures [EXPAND_COLLAPSE_CURSOR_ROW], false);
    if (checkRenderer !is null) {
        OS.g_signal_connect_closure (checkRenderer, OS.toggled.ptr, display.closures [TOGGLED], false);
    }
}

/**
 * Searches the receiver's list starting at the first column
 * (index 0) until a column is found that is equal to the
 * argument, and returns the index of that column. If no column
 * is found, returns -1.
 *
 * @param column the search column
 * @return the index of the column
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the column is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public int indexOf (TreeColumn column) {
    checkWidget();
    if (column is null) error (SWT.ERROR_NULL_ARGUMENT);
    for (int i=0; i<columnCount; i++) {
        if (columns [i] is column) return i;
    }
    return -1;
}

/**
 * Searches the receiver's list starting at the first item
 * (index 0) until an item is found that is equal to the
 * argument, and returns the index of that item. If no item
 * is found, returns -1.
 *
 * @param item the search item
 * @return the index of the item
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the item is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the item has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public int indexOf (TreeItem item) {
    checkWidget();
    if (item is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (item.isDisposed()) error (SWT.ERROR_INVALID_ARGUMENT);
    int index = -1;
    auto path = OS.gtk_tree_model_get_path (modelHandle, item.handle);
    int depth = OS.gtk_tree_path_get_depth (path);
    if (depth is 1) {
        auto indices = OS.gtk_tree_path_get_indices (path);
        if (indices !is null) {
            index = indices[0];
        }
    }
    OS.gtk_tree_path_free (path);
    return index;
}

override bool mnemonicHit (wchar key) {
    for (int i=0; i<columnCount; i++) {
        auto labelHandle = columns [i].labelHandle;
        if (labelHandle !is null && mnemonicHit (labelHandle, key)) return true;
    }
    return false;
}

override bool mnemonicMatch (wchar key) {
    for (int i=0; i<columnCount; i++) {
        auto labelHandle = columns [i].labelHandle;
        if (labelHandle !is null && mnemonicMatch (labelHandle, key)) return true;
    }
    return false;
}

override GdkDrawable* paintWindow () {
    OS.gtk_widget_realize (handle);
    return OS.gtk_tree_view_get_bin_window (handle);
}

void recreateRenderers () {
    if (checkRenderer !is null) {
        display.removeWidget (cast(GtkWidget*)checkRenderer);
        OS.g_object_unref (checkRenderer);
        checkRenderer = ownerDraw ? cast(GtkCellRenderer*)OS.g_object_new (display.gtk_cell_renderer_toggle_get_type(), null) : OS.gtk_cell_renderer_toggle_new ();
        if (checkRenderer is null) error (SWT.ERROR_NO_HANDLES);
        OS.g_object_ref (checkRenderer);
        display.addWidget (cast(GtkWidget*)checkRenderer, this);
        OS.g_signal_connect_closure (checkRenderer, OS.toggled.ptr, display.closures [TOGGLED], false);
    }
    if (columnCount is 0) {
        createRenderers (OS.gtk_tree_view_get_column (handle, 0), Tree.FIRST_COLUMN, true, 0);
    } else {
        for (int i = 0; i < columnCount; i++) {
            TreeColumn column = columns [i];
            createRenderers (cast(GtkTreeViewColumn*)column.handle, column.modelIndex, i is 0, column.style);
        }
    }
}

override void redrawBackgroundImage () {
    Control control = findBackgroundControl ();
    if (control !is null && control.backgroundImage !is null) {
        redrawWidget (0, 0, 0, 0, true, false, false);
    }
}

override void register () {
    super.register ();
    display.addWidget (cast(GtkWidget*)OS.gtk_tree_view_get_selection (handle), this);
    if (checkRenderer !is null) display.addWidget (cast(GtkWidget*)checkRenderer, this);
}

void releaseItem (TreeItem item, bool release) {
    int index;
    OS.gtk_tree_model_get1 (modelHandle, item.handle, ID_COLUMN, cast(void**)&index);
    if (index is -1) return;
    if (release) item.release (false);
    items [index ] = null;
}

void releaseItems (GtkTreeIter* parentIter) {
    int index;
    GtkTreeIter iter;
    bool valid = cast(bool)OS.gtk_tree_model_iter_children (modelHandle, &iter, parentIter);
    while (valid) {
        releaseItems (&iter);
        if (!isDisposed ()) {
            OS.gtk_tree_model_get1 (modelHandle, &iter, ID_COLUMN, cast(void**)&index);
            if (index  !is -1) {
                TreeItem item = items [index ];
                if (item !is null) releaseItem (item, true);
            }
        }
        valid = cast(bool)OS.gtk_tree_model_iter_next (modelHandle, &iter);
    }
}

override void releaseChildren (bool destroy) {
    if (items !is null) {
        for (int i=0; i<items.length; i++) {
            TreeItem item = items [i];
            if (item !is null && !item.isDisposed ()) {
                item.release (false);
            }
        }
        items = null;
    }
    if (columns !is null) {
        for (int i=0; i<columnCount; i++) {
            TreeColumn column = columns [i];
            if (column !is null && !column.isDisposed ()) {
                column.release (false);
            }
        }
        columns = null;
    }
    super.releaseChildren (destroy);
}

override void releaseWidget () {
    super.releaseWidget ();
    if (modelHandle !is null) OS.g_object_unref (modelHandle);
    modelHandle = null;
    if (checkRenderer !is null) OS.g_object_unref (checkRenderer);
    checkRenderer = null;
    if (imageList !is null) imageList.dispose ();
    if (headerImageList !is null) headerImageList.dispose ();
    imageList = headerImageList = null;
    currentItem = null;
}

void remove (GtkTreeIter* parentIter, int start, int end) {
    if (start > end) return;
    int itemCount = OS.gtk_tree_model_iter_n_children (modelHandle, parentIter);
    if (!(0 <= start && start <= end && end < itemCount)) {
        error (SWT.ERROR_INVALID_RANGE);
    }
    auto selection = OS.gtk_tree_view_get_selection (handle);
    GtkTreeIter iter;
    int index = start;
    for (int i = start; i <= end; i++) {
        OS.gtk_tree_model_iter_nth_child (modelHandle, &iter, parentIter, index);
        int value;
        OS.gtk_tree_model_get1 (modelHandle, &iter, ID_COLUMN, cast(void**)&value);
        TreeItem item = value  !is -1 ? items [value ] : null;
        if (item !is null && !item.isDisposed ()) {
            item.dispose ();
        } else {
            OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
            OS.gtk_tree_store_remove (modelHandle, &iter);
            OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
        }
    }
}

/**
 * Removes all of the items from the receiver.
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void removeAll () {
    checkWidget ();
    for (int i=0; i<items.length; i++) {
        TreeItem item = items [i];
        if (item !is null && !item.isDisposed ()) item.release (false);
    }
    items = new TreeItem[4];
    auto selection = OS.gtk_tree_view_get_selection (handle);
    OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    OS.gtk_tree_store_clear (modelHandle);
    OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);

    /* Disable searching when using VIRTUAL */
    if ((style & SWT.VIRTUAL) !is 0) {
        /*
        * Bug in GTK. Until GTK 2.6.5, calling gtk_tree_view_set_enable_search(FALSE)
        * would prevent the user from being able to type in text to search the tree.
        * After 2.6.5, GTK introduced Ctrl+F as being the key binding for interactive
        * search. This meant that even if FALSE was passed to enable_search, the user
        * can still bring up the search pop up using the keybinding. GTK also introduced
        * the notion of passing a -1 to gtk_set_search_column to disable searching
        * (including the search key binding).  The fix is to use the right calls
        * for the right version.
        */
        if (OS.GTK_VERSION >= OS.buildVERSION (2, 6, 5)) {
            OS.gtk_tree_view_set_search_column (handle, -1);
        } else {
            OS.gtk_tree_view_set_enable_search (handle, false);
        }
    } else {
        /* Set the search column whenever the model changes */
        int firstColumn = columnCount is 0 ? FIRST_COLUMN : columns [0].modelIndex;
        OS.gtk_tree_view_set_search_column (handle, firstColumn + CELL_TEXT);
    }
}

/**
 * Removes the listener from the collection of listeners who will
 * be notified when the user changes the receiver's selection.
 *
 * @param listener the listener which should no longer be notified
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see SelectionListener
 * @see #addSelectionListener
 */
public void removeSelectionListener (SelectionListener listener) {
    checkWidget ();
    if (listener is null) error (SWT.ERROR_NULL_ARGUMENT);
    eventTable.unhook (SWT.Selection, listener);
    eventTable.unhook (SWT.DefaultSelection, listener);
}

/**
 * Removes the listener from the collection of listeners who will
 * be notified when items in the receiver are expanded or collapsed.
 *
 * @param listener the listener which should no longer be notified
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see TreeListener
 * @see #addTreeListener
 */
public void removeTreeListener(TreeListener listener) {
    checkWidget ();
    if (listener is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (eventTable is null) return;
    eventTable.unhook (SWT.Expand, listener);
    eventTable.unhook (SWT.Collapse, listener);
}

override void rendererGetSizeProc (
    GtkCellRenderer      *cell,
    GtkWidget            *widget,
    GdkRectangle         *cell_area,
    int                  *x_offset,
    int                  *y_offset,
    int                  *width,
    int                  *height)
{
    auto g_class = OS.g_type_class_peek_parent (OS.G_OBJECT_GET_CLASS (cell));
    GtkCellRendererClass* klass = cast(GtkCellRendererClass*)g_class;
    klass.get_size( cell, handle, cell_area, x_offset, y_offset, width, height);
    if (!ignoreSize && OS.GTK_IS_CELL_RENDERER_TEXT (cell)) {
        auto iter = cast(GtkTreeIter*)OS.g_object_get_qdata (cast(GObject*)cell, Display.SWT_OBJECT_INDEX2);
        TreeItem item = null;
        if (iter !is null) item = _getItem (iter);
        if (item !is null) {
            int columnIndex = 0;
            if (columnCount > 0) {
                auto columnHandle = cast(GtkTreeViewColumn*)OS.g_object_get_qdata (cast(GObject*)cell, Display.SWT_OBJECT_INDEX1);
                for (int i = 0; i < columnCount; i++) {
                    if (columns [i].handle is cast(GtkWidget*)columnHandle) {
                        columnIndex = i;
                        break;
                    }
                }
            }
            if (hooks (SWT.MeasureItem)) {
                int contentWidth, contentHeight;
                if (width !is null) contentWidth = *width;
                if (height !is null) contentHeight = *height;
                Image image = item.getImage (columnIndex);
                int imageWidth = 0;
                if (image !is null) {
                    Rectangle bounds = image.getBounds ();
                    imageWidth = bounds.width;
                }
                contentWidth += imageWidth;
                GC gc = new GC (this);
                gc.setFont (item.getFont (columnIndex));
                Event event = new Event ();
                event.item = item;
                event.index = columnIndex;
                event.gc = gc;
                event.width = contentWidth ;
                event.height = contentHeight ;
                sendEvent (SWT.MeasureItem, event);
                gc.dispose ();
                contentWidth  = event.width - imageWidth;
                if (contentHeight < event.height) contentHeight = event.height;
                if (width !is null) *width = contentWidth;
                if (height !is null) *height = contentHeight;
            }
        }
    }
}

override void rendererRenderProc (
    GtkCellRenderer * cell,
    GdkDrawable * window,
    GtkWidget * widget,
    GdkRectangle *background_area,
    GdkRectangle *cell_area,
    GdkRectangle *expose_area,
    int flags)
{
    TreeItem item = null;
    auto iter = cast(GtkTreeIter*)OS.g_object_get_qdata (cast(GObject*)cell, Display.SWT_OBJECT_INDEX2);
    if (iter !is null) item = _getItem (iter);
    auto columnHandle = cast(GtkTreeViewColumn*)OS.g_object_get_qdata (cast(GObject*)cell, Display.SWT_OBJECT_INDEX1);
    int columnIndex = 0;
    if (columnCount > 0) {
        for (int i = 0; i < columnCount; i++) {
            if (columns [i].handle is cast(GtkWidget*)columnHandle) {
                columnIndex = i;
                break;
            }
        }
    }
    if (item !is null) {
        if (OS.GTK_IS_CELL_RENDERER_TOGGLE (cell) || (OS.GTK_IS_CELL_RENDERER_PIXBUF (cell) && (columnIndex !is 0 || (style & SWT.CHECK) is 0))) {
            drawFlags = flags;
            drawState = SWT.FOREGROUND;
            void* ptr;
            OS.gtk_tree_model_get1 (modelHandle, item.handle, Tree.BACKGROUND_COLUMN, &ptr);
            if (ptr is null) {
                int modelIndex = columnCount is 0 ? Tree.FIRST_COLUMN : columns [columnIndex].modelIndex;
                OS.gtk_tree_model_get1 (modelHandle, item.handle, modelIndex + Tree.CELL_BACKGROUND, &ptr);
            }
            if (ptr !is null) drawState |= SWT.BACKGROUND;
            if ((flags & OS.GTK_CELL_RENDERER_SELECTED) !is 0) drawState |= SWT.SELECTED;
            if ((flags & OS.GTK_CELL_RENDERER_FOCUSED) !is 0) drawState |= SWT.FOCUSED;

            GdkRectangle rect;
            auto path = OS.gtk_tree_model_get_path (modelHandle, iter);
            OS.gtk_tree_view_get_background_area (handle, path, columnHandle, &rect);
            OS.gtk_tree_path_free (path);

            if ((drawState & SWT.SELECTED) is 0) {
                Control control = findBackgroundControl ();
                if (control !is null && control.backgroundImage !is null) {
                    OS.gdk_window_clear_area (window, rect.x, rect.y, rect.width, rect.height);
                }
            }

            if (hooks (SWT.EraseItem)) {
                bool wasSelected = false;
                if ((drawState & SWT.SELECTED) !is 0) {
                    wasSelected = true;
                    OS.gdk_window_clear_area (window, rect.x, rect.y, rect.width, rect.height);
                }
                GC gc = new GC (this);
                if ((drawState & SWT.SELECTED) !is 0) {
                    gc.setBackground (display.getSystemColor (SWT.COLOR_LIST_SELECTION));
                    gc.setForeground (display.getSystemColor (SWT.COLOR_LIST_SELECTION_TEXT));
                } else {
                    gc.setBackground (item.getBackground (columnIndex));
                    gc.setForeground (item.getForeground (columnIndex));
                }
                gc.setFont (item.getFont (columnIndex));
                if ((style & SWT.MIRRORED) !is 0) rect.x = getClientWidth () - rect.width - rect.x;
                gc.setClipping (rect.x, rect.y, rect.width, rect.height);
                Event event = new Event ();
                event.item = item;
                event.index = columnIndex;
                event.gc = gc;
                event.x = rect.x;
                event.y = rect.y;
                event.width = rect.width;
                event.height = rect.height;
                event.detail = drawState;
                sendEvent (SWT.EraseItem, event);
                drawForeground = null;
                drawState = event.doit ? event.detail : 0;
                drawFlags &= ~(OS.GTK_CELL_RENDERER_FOCUSED | OS.GTK_CELL_RENDERER_SELECTED);
                if ((drawState & SWT.SELECTED) !is 0) drawFlags |= OS.GTK_CELL_RENDERER_SELECTED;
                if ((drawState & SWT.FOCUSED) !is 0) drawFlags |= OS.GTK_CELL_RENDERER_FOCUSED;
                if ((drawState & SWT.SELECTED) !is 0) {
                    auto style = OS.gtk_widget_get_style (widget);
                    //TODO - parity and sorted
                    OS.gtk_paint_flat_box (style, window, OS.GTK_STATE_SELECTED, OS.GTK_SHADOW_NONE, &rect, widget, "cell_odd".ptr, rect.x, rect.y, rect.width, rect.height);
                } else {
                    if (wasSelected) drawForeground = gc.getForeground ().handle;
                }
                gc.dispose();
            }
        }
    }
    int result = 0;
    if ((drawState & SWT.BACKGROUND) !is 0 && (drawState & SWT.SELECTED) is 0) {
        GC gc = new GC (this);
        gc.setBackground (item.getBackground (columnIndex));
        gc.fillRectangle (background_area.x, background_area.y, background_area.width, background_area.height);
        gc.dispose ();
    }
    if ((drawState & SWT.FOREGROUND) !is 0 || OS.GTK_IS_CELL_RENDERER_TOGGLE (cell)) {
        auto g_class = OS.g_type_class_peek_parent (OS.G_OBJECT_GET_CLASS (cell));
        GtkCellRendererClass* klass = cast(GtkCellRendererClass*)g_class;
        if (drawForeground !is null && OS.GTK_IS_CELL_RENDERER_TEXT (cell)) {
            OS.g_object_set1 (cell, OS.foreground_gdk.ptr, cast(ptrdiff_t)drawForeground);
        }
        klass.render( cell, window, handle, background_area, cell_area, expose_area, drawFlags);
    }
    if (item !is null) {
        if (OS.GTK_IS_CELL_RENDERER_TEXT (cell)) {
            if (hooks (SWT.PaintItem)) {
                GdkRectangle rect;
                auto path = OS.gtk_tree_model_get_path (modelHandle, iter);
                OS.gtk_tree_view_get_cell_area (handle, path, columnHandle, &rect);
                OS.gtk_tree_path_free (path);
                if (OS.GTK_VERSION < OS.buildVERSION (2, 8, 18) && OS.gtk_tree_view_get_expander_column (handle) is columnHandle) {
                    int buffer;
                    OS.gtk_widget_style_get1 (handle, OS.expander_size.ptr, &buffer);
                    rect.x += buffer + TreeItem.EXPANDER_EXTRA_PADDING;
                    rect.width -= buffer + TreeItem.EXPANDER_EXTRA_PADDING;
                    //OS.gtk_widget_style_get (handle, OS.horizontal_separator, buffer, 0);
                    //rect.x += buffer[0];
                    //rect.width -= buffer [0]; // TODO Is this required for some versions?
                }
                ignoreSize = true;
                int contentX, contentWidth;
                OS.gtk_cell_renderer_get_size (cell, handle, null, null, null, &contentWidth, null);
                OS.gtk_tree_view_column_cell_get_position (columnHandle, cell, &contentX, null);
                ignoreSize = false;
                Image image = item.getImage (columnIndex);
                int imageWidth = 0;
                if (image !is null) {
                    Rectangle bounds = image.getBounds ();
                    imageWidth = bounds.width;
                }
                contentX -= imageWidth;
                contentWidth += imageWidth;
                GC gc = new GC (this);
                if ((drawState & SWT.SELECTED) !is 0) {
                    gc.setBackground (display.getSystemColor (SWT.COLOR_LIST_SELECTION));
                    gc.setForeground (display.getSystemColor (SWT.COLOR_LIST_SELECTION_TEXT));
                } else {
                    gc.setBackground (item.getBackground (columnIndex));
                    Color foreground = drawForeground !is null ? Color.gtk_new (display, drawForeground) : item.getForeground (columnIndex);
                    gc.setForeground (foreground);
                }
                gc.setFont (item.getFont (columnIndex));
                if ((style & SWT.MIRRORED) !is 0) rect.x = getClientWidth () - rect.width - rect.x;
                gc.setClipping (rect.x, rect.y, rect.width, rect.height);
                Event event = new Event ();
                event.item = item;
                event.index = columnIndex;
                event.gc = gc;
                event.x = rect.x + contentX;
                event.y = rect.y;
                event.width = contentWidth;
                event.height = rect.height;
                event.detail = drawState;
                sendEvent (SWT.PaintItem, event);
                gc.dispose();
            }
        }
    }
    //return result;
}

void resetCustomDraw () {
    if ((style & SWT.VIRTUAL) !is 0 || ownerDraw) return;
    int end = Math.max (1, columnCount);
    for (int i=0; i<end; i++) {
        bool customDraw = columnCount !is 0 ? columns [i].customDraw : firstCustomDraw;
        if (customDraw) {
            auto column = OS.gtk_tree_view_get_column (handle, i);
            auto textRenderer = getTextRenderer (column);
            OS.gtk_tree_view_column_set_cell_data_func (column, textRenderer, null, null, null);
            if (columnCount !is 0) columns [i].customDraw = false;
        }
    }
    firstCustomDraw = false;
}

/**
 * Display a mark indicating the point at which an item will be inserted.
 * The drop insert item has a visual hint to show where a dragged item
 * will be inserted when dropped on the tree.
 *
 * @param item the insert item.  Null will clear the insertion mark.
 * @param before true places the insert mark above 'item'. false places
 *  the insert mark below 'item'.
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_INVALID_ARGUMENT - if the item has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void setInsertMark (TreeItem item, bool before) {
    checkWidget ();
    if (item is null) {
        OS.gtk_tree_view_set_drag_dest_row(handle, null, OS.GTK_TREE_VIEW_DROP_BEFORE);
        return;
    }
    if (item.isDisposed()) error (SWT.ERROR_INVALID_ARGUMENT);
    if (item.parent !is this) return;
    Rectangle rect = item.getBounds();
    void* path;
    OS.gtk_widget_realize (handle);
    if (!OS.gtk_tree_view_get_path_at_pos(handle, rect.x, rect.y, &path, null, null, null)) return;
    if (path is null) return;
    int position = before ? OS.GTK_TREE_VIEW_DROP_BEFORE : OS.GTK_TREE_VIEW_DROP_AFTER;
    OS.gtk_tree_view_set_drag_dest_row(handle, path, position);
    OS.gtk_tree_path_free (path );
}

void setItemCount (GtkTreeIter* parentIter, int count) {
    int itemCount = OS.gtk_tree_model_iter_n_children (modelHandle, parentIter);
    if (count is itemCount) return;
    bool isVirtual = (style & SWT.VIRTUAL) !is 0;
    if (!isVirtual) setRedraw (false);
    remove (parentIter, count, itemCount - 1);
    if (isVirtual) {
        for (int i=itemCount; i<count; i++) {
            GtkTreeIter iter;
            OS.gtk_tree_store_append (modelHandle, &iter, parentIter);
            OS.gtk_tree_store_set1 (modelHandle, &iter, ID_COLUMN, cast(void*)-1);
        }
    } else {
        for (int i=itemCount; i<count; i++) {
            new TreeItem (this, parentIter, SWT.NONE, i, true);
        }
    }
    if (!isVirtual) setRedraw (true);
    modelChanged = true;
}

/**
 * Sets the number of root-level items contained in the receiver.
 *
 * @param count the number of items
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.2
 */
public void setItemCount (int count) {
    checkWidget ();
    count = Math.max (0, count);
    setItemCount (null, count);
}

/**
 * Selects an item in the receiver.  If the item was already
 * selected, it remains selected.
 *
 * @param item the item to be selected
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the item is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the item has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.4
 */
public void select (TreeItem item) {
    checkWidget ();
    if (item is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (item.isDisposed ()) error (SWT.ERROR_INVALID_ARGUMENT);
    bool fixColumn = showFirstColumn ();
    auto selection = OS.gtk_tree_view_get_selection (handle);
    OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    OS.gtk_tree_selection_select_iter (selection, item.handle);
    OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    if (fixColumn) hideFirstColumn ();
}

/**
 * Selects all of the items in the receiver.
 * <p>
 * If the receiver is single-select, do nothing.
 * </p>
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void selectAll () {
    checkWidget();
    if ((style & SWT.SINGLE) !is 0) return;
    bool fixColumn = showFirstColumn ();
    auto selection = OS.gtk_tree_view_get_selection (handle);
    OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    OS.gtk_tree_selection_select_all (selection);
    OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    if (fixColumn) hideFirstColumn ();
}

override void setBackgroundColor (GdkColor* color) {
    super.setBackgroundColor (color);
    OS.gtk_widget_modify_base (handle, 0, color);
}

override void setBackgroundPixmap (GdkPixmap* pixmap) {
    super.setBackgroundPixmap (pixmap);
    auto window = paintWindow ();
    if (window !is null) OS.gdk_window_set_back_pixmap (window, null, true);
}

override int setBounds (int x, int y, int width, int height, bool move, bool resize) {
    int result = super.setBounds (x, y, width, height, move, resize);
    /*
    * Bug on GTK.  The tree view sometimes does not get a paint
    * event or resizes to a one pixel square when resized in a new
    * shell that is not visible after any event loop has been run.  The
    * problem is intermittent. It doesn't seem to happen the first time
    * a new shell is created. The fix is to ensure the tree view is realized
    * after it has been resized.
    */
    OS.gtk_widget_realize (handle);
    /*
    * Bug in GTK.  An empty GtkTreeView fails to repaint the focus rectangle
    * correctly when resized on versions before 2.6.0.  The fix is to force
    * the widget to redraw.
    */
    if (OS.GTK_VERSION < OS.buildVERSION (2, 6, 0) && OS.gtk_tree_model_iter_n_children (modelHandle, null) is 0) {
        redraw (false);
    }
    return result;
}

/**
 * Sets the order that the items in the receiver should
 * be displayed in to the given argument which is described
 * in terms of the zero-relative ordering of when the items
 * were added.
 *
 * @param order the new order to display the items
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_INVALID_ARGUMENT - if the item order is not the same length as the number of items</li>
 * </ul>
 *
 * @see Tree#getColumnOrder()
 * @see TreeColumn#getMoveable()
 * @see TreeColumn#setMoveable(bool)
 * @see SWT#Move
 *
 * @since 3.2
 */
public void setColumnOrder (int [] order) {
    checkWidget ();
    // SWT extension: allow null for zero length string
    //if (order is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (columnCount is 0) {
        if (order.length > 0) error (SWT.ERROR_INVALID_ARGUMENT);
        return;
    }
    if (order.length !is columnCount) error (SWT.ERROR_INVALID_ARGUMENT);
    bool [] seen = new bool [columnCount];
    for (int i = 0; i<order.length; i++) {
        int index = order [i];
        if (index < 0 || index >= columnCount) error (SWT.ERROR_INVALID_RANGE);
        if (seen [index]) error (SWT.ERROR_INVALID_ARGUMENT);
        seen [index] = true;
    }
    void* baseColumn;
    for (int i=0; i<order.length; i++) {
        auto column = columns [order [i]].handle;
        OS.gtk_tree_view_move_column_after (handle, column, baseColumn);
        baseColumn = column;
    }
}

override void setFontDescription (PangoFontDescription* font) {
    super.setFontDescription (font);
    TreeColumn[] columns = getColumns ();
    for (int i = 0; i < columns.length; i++) {
        if (columns[i] !is null) {
            columns[i].setFontDescription (font);
        }
    }
}

/**
 * Marks the receiver's header as visible if the argument is <code>true</code>,
 * and marks it invisible otherwise.
 * <p>
 * If one of the receiver's ancestors is not visible or some
 * other condition makes the receiver not visible, marking
 * it visible may not actually cause it to be displayed.
 * </p>
 *
 * @param show the new visibility state
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public void setHeaderVisible (bool show) {
    checkWidget ();
    OS.gtk_tree_view_set_headers_visible (handle, show);
}

/**
 * Marks the receiver's lines as visible if the argument is <code>true</code>,
 * and marks it invisible otherwise.
 * <p>
 * If one of the receiver's ancestors is not visible or some
 * other condition makes the receiver not visible, marking
 * it visible may not actually cause it to be displayed.
 * </p>
 *
 * @param show the new visibility state
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public void setLinesVisible (bool show) {
    checkWidget();
    OS.gtk_tree_view_set_rules_hint (handle, show);
}

override void setParentBackground () {
    super.setParentBackground ();
    auto window = paintWindow ();
    if (window !is null) OS.gdk_window_set_back_pixmap (window, null, true);
}

override void setParentWindow (GtkWidget* widget) {
    auto window = eventWindow ();
    OS.gtk_widget_set_parent_window (widget, window);
}

void setScrollWidth (GtkTreeViewColumn* column, TreeItem item) {
    if (columnCount !is 0 || currentItem is item) return;
    /*
    * Use GTK_TREE_VIEW_COLUMN_GROW_ONLY on GTK versions < 2.3.2
    * because fixed_height_mode is not supported.
    */
    if (((style & SWT.VIRTUAL) !is 0) && OS.GTK_VERSION < OS.buildVERSION (2, 3, 2)) return;
    int width = OS.gtk_tree_view_column_get_fixed_width (column);
    int itemWidth = calculateWidth (column, cast(GtkTreeIter*)item.handle, true);
    if (width < itemWidth) {
        OS.gtk_tree_view_column_set_fixed_width (column, itemWidth);
    }
}

/**
 * Sets the receiver's selection to the given item.
 * The current selection is cleared before the new item is selected.
 * <p>
 * If the item is not in the receiver, then it is ignored.
 * </p>
 *
 * @param item the item to select
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the item is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the item has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.2
 */
public void setSelection (TreeItem item) {
    checkWidget ();
    if (item is null) error (SWT.ERROR_NULL_ARGUMENT);
    setSelection ([item]);
}

/**
 * Sets the receiver's selection to be the given array of items.
 * The current selection is cleared before the new items are selected.
 * <p>
 * Items that are not in the receiver are ignored.
 * If the receiver is single-select and multiple items are specified,
 * then all items are ignored.
 * </p>
 *
 * @param items the array of items
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_INVALID_ARGUMENT - if one of the items has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see Tree#deselectAll()
 */
public void setSelection (TreeItem [] items) {
    checkWidget ();
    // SWT extension: allow null for zero length string
    //if (items is null) error (SWT.ERROR_NULL_ARGUMENT);
    deselectAll ();
    ptrdiff_t length = items.length;
    if (length is 0 || ((style & SWT.SINGLE) !is 0 && length > 1)) return;
    bool fixColumn = showFirstColumn ();
    auto selection = OS.gtk_tree_view_get_selection (handle);
    OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    bool first = true;
    for (int i = 0; i < length; i++) {
        TreeItem item = items [i];
        if (item is null) continue;
        if (item.isDisposed ()) break;
        if (item.parent !is this) continue;
        auto path = OS.gtk_tree_model_get_path (modelHandle, item.handle);
        showItem (path, false);
        if (first) {
            OS.gtk_tree_view_set_cursor (handle, path, null, false);
        }
        OS.gtk_tree_selection_select_iter (selection, item.handle);
        OS.gtk_tree_path_free (path);
        first = false;
    }
    OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, null, null, udCHANGED);
    if (fixColumn) hideFirstColumn ();
}

/**
 * Sets the column used by the sort indicator for the receiver. A null
 * value will clear the sort indicator.  The current sort column is cleared
 * before the new column is set.
 *
 * @param column the column used by the sort indicator or <code>null</code>
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_INVALID_ARGUMENT - if the column is disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.2
 */
public void setSortColumn (TreeColumn column) {
    checkWidget ();
    if (column !is null && column.isDisposed ()) error (SWT.ERROR_INVALID_ARGUMENT);
    if (sortColumn !is null && !sortColumn.isDisposed()) {
        OS.gtk_tree_view_column_set_sort_indicator (sortColumn.handle, false);
    }
    sortColumn = column;
    if (sortColumn !is null && sortDirection !is SWT.NONE) {
        OS.gtk_tree_view_column_set_sort_indicator (sortColumn.handle, true);
        OS.gtk_tree_view_column_set_sort_order (sortColumn.handle, sortDirection is SWT.DOWN ? 0 : 1);
    }
}

/**
 * Sets the direction of the sort indicator for the receiver. The value
 * can be one of <code>UP</code>, <code>DOWN</code> or <code>NONE</code>.
 *
 * @param direction the direction of the sort indicator
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.2
 */
public void setSortDirection  (int direction) {
    checkWidget ();
    if (direction !is SWT.UP && direction !is SWT.DOWN && direction !is SWT.NONE) return;
    sortDirection = direction;
    if (sortColumn is null || sortColumn.isDisposed ()) return;
    if (sortDirection is SWT.NONE) {
        OS.gtk_tree_view_column_set_sort_indicator (sortColumn.handle, false);
    } else {
        OS.gtk_tree_view_column_set_sort_indicator (sortColumn.handle, true);
        OS.gtk_tree_view_column_set_sort_order (sortColumn.handle, sortDirection is SWT.DOWN ? 0 : 1);
    }
}

/**
 * Sets the item which is currently at the top of the receiver.
 * This item can change when items are expanded, collapsed, scrolled
 * or new items are added or removed.
 *
 * @param item the item to be shown
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the item is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the item has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see Tree#getTopItem()
 *
 * @since 2.1
 */
public void setTopItem (TreeItem item) {
    if (item is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (item.isDisposed ()) error(SWT.ERROR_INVALID_ARGUMENT);
    if (item.parent !is this) return;
    auto path = OS.gtk_tree_model_get_path (modelHandle, item.handle);
    showItem (path, false);
    OS.gtk_tree_view_scroll_to_cell (handle, path, null, true, 0f, 0f);
    if (OS.GTK_VERSION < OS.buildVERSION (2, 8, 0)) {
        /*
        * Bug in GTK.  According to the documentation, gtk_tree_view_scroll_to_cell
        * should vertically scroll the cell to the top if use_align is true and row_align is 0.
        * However, prior to version 2.8 it does not scroll at all.  The fix is to determine
        * the new location and use gtk_tree_view_scroll_to_point.
        * If the widget is a pinhead, calling gtk_tree_view_scroll_to_point
        * will have no effect. Therefore, it is still neccessary to call
        * gtk_tree_view_scroll_to_cell.
        */
        OS.gtk_widget_realize (handle);
        GdkRectangle cellRect;
        OS.gtk_tree_view_get_cell_area (handle, path, null, &cellRect);
        int tx, ty;
        OS.gtk_tree_view_widget_to_tree_coords(handle, cellRect.x, cellRect.y, &tx, &ty);
        OS.gtk_tree_view_scroll_to_point (handle, -1, ty);
    }
    OS.gtk_tree_path_free (path);
}

/**
 * Shows the column.  If the column is already showing in the receiver,
 * this method simply returns.  Otherwise, the columns are scrolled until
 * the column is visible.
 *
 * @param column the column to be shown
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the item is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the item has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @since 3.1
 */
public void showColumn (TreeColumn column) {
    checkWidget ();
    if (column is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (column.isDisposed()) error(SWT.ERROR_INVALID_ARGUMENT);
    if (column.parent !is this) return;
    /*
    * This code is intentionally commented. According to the
    * documentation, gtk_tree_view_scroll_to_cell should scroll the
    * minimum amount to show the column but instead it scrolls strangely.
    */
    //OS.gtk_tree_view_scroll_to_cell (handle, 0, column.handle, false, 0, 0);
    OS.gtk_widget_realize (handle);
    GdkRectangle cellRect;
    OS.gtk_tree_view_get_cell_area (handle, null, column.handle, &cellRect);
    GdkRectangle visibleRect;
    OS.gtk_tree_view_get_visible_rect (handle, &visibleRect);
    if (cellRect.x < visibleRect.x) {
        OS.gtk_tree_view_scroll_to_point (handle, cellRect.x, -1);
    } else {
        int width = Math.min (visibleRect.width, cellRect.width);
        if (cellRect.x + width > visibleRect.x + visibleRect.width) {
            int tree_x = cellRect.x + width - visibleRect.width;
            OS.gtk_tree_view_scroll_to_point (handle, tree_x, -1);
        }
    }
}

bool showFirstColumn () {
    /*
    * Bug in GTK.  If no columns are visible, changing the selection
    * will fail.  The fix is to temporarily make a column visible.
    */
    int columnCount = Math.max (1, this.columnCount);
    for (int i=0; i<columnCount; i++) {
        auto column = OS.gtk_tree_view_get_column (handle, i);
        if (OS.gtk_tree_view_column_get_visible (column)) return false;
    }
    auto firstColumn = OS.gtk_tree_view_get_column (handle, 0);
    OS.gtk_tree_view_column_set_visible (firstColumn, true);
    return true;
}

/**
 * Shows the selection.  If the selection is already showing in the receiver,
 * this method simply returns.  Otherwise, the items are scrolled until
 * the selection is visible.
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see Tree#showItem(TreeItem)
 */
public void showSelection () {
    checkWidget();
    TreeItem [] items = getSelection ();
    if (items.length !is 0 && items [0] !is null) showItem (items [0]);
}

void showItem (GtkTreePath* path, bool scroll) {
    int depth = OS.gtk_tree_path_get_depth (path);
    if (depth > 1) {
        auto indicesPtr = OS.gtk_tree_path_get_indices (path);
        int [] indices = indicesPtr[ 0 .. depth - 1];
        auto tempPath = OS.gtk_tree_path_new ();
        for (int i=0; i<indices.length; i++) {
            OS.gtk_tree_path_append_index (tempPath, indices [i]);
            OS.gtk_tree_view_expand_row (handle, tempPath, false);
        }
        OS.gtk_tree_path_free (tempPath);
    }
    if (scroll) {
        OS.gtk_widget_realize (handle);
        GdkRectangle cellRect;
        OS.gtk_tree_view_get_cell_area (handle, path, null, &cellRect);
        bool isHidden = cellRect.y is 0 && cellRect.height is 0;
        int tx, ty;
        OS.gtk_tree_view_widget_to_tree_coords (handle, cellRect.x, cellRect.y, &tx, &ty);
        GdkRectangle visibleRect;
        OS.gtk_tree_view_get_visible_rect (handle, &visibleRect);
        if (!isHidden) {
            if (ty < visibleRect.y || ty + cellRect.height > visibleRect.y + visibleRect.height) {
                isHidden = true;
            }
        }
        if (isHidden) {
            /*
            * This code intentionally commented.
            * Bug in GTK.  According to the documentation, gtk_tree_view_scroll_to_cell
            * should scroll the minimum amount to show the cell if use_align is false.
            * However, what actually happens is the cell is scrolled to the top.
            * The fix is to determine the new location and use gtk_tree_view_scroll_to_point.
            * If the widget is a pinhead, calling gtk_tree_view_scroll_to_point
            * will have no effect. Therefore, it is still neccessary to
            * call gtk_tree_view_scroll_to_cell.
            */
            //  OS.gtk_tree_view_scroll_to_cell (handle, path, 0, depth !is 1, 0.5f, 0.0f);
            if (depth !is 1) {
                OS.gtk_tree_view_scroll_to_cell (handle, path, null, true, 0.5f, 0.0f);
            } else {
                if (ty < visibleRect.y ) {
                    OS.gtk_tree_view_scroll_to_point (handle, -1, ty);
                } else {
                    int height = Math.min (visibleRect.height, cellRect.height);
                    if (ty + height > visibleRect.y + visibleRect.height) {
                        OS.gtk_tree_view_scroll_to_point (handle, -1, ty + cellRect.height - visibleRect.height);
                    }
                }
            }
        }
    }
}

/**
 * Shows the item.  If the item is already showing in the receiver,
 * this method simply returns.  Otherwise, the items are scrolled
 * and expanded until the item is visible.
 *
 * @param item the item to be shown
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the item is null</li>
 *    <li>ERROR_INVALID_ARGUMENT - if the item has been disposed</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see Tree#showSelection()
 */
public void showItem (TreeItem item) {
    checkWidget ();
    if (item is null) error (SWT.ERROR_NULL_ARGUMENT);
    if (item.isDisposed ()) error(SWT.ERROR_INVALID_ARGUMENT);
    if (item.parent !is this) return;
    auto path = OS.gtk_tree_model_get_path (modelHandle, item.handle);
    showItem (path, true);
    OS.gtk_tree_path_free (path);
}

override void treeSelectionProc (
    GtkTreeModel *model,
    GtkTreePath *path,
    GtkTreeIter *iter,
    int[] selection,
    int length_)
{
    if (selection !is null) {
        int index;
        OS.gtk_tree_model_get1 (modelHandle, iter, ID_COLUMN, cast(void**)&index);
        selection [length_] = index;
    }
}

override void updateScrollBarValue (ScrollBar bar) {
    super.updateScrollBarValue (bar);
    /*
    * Bug in GTK. Scrolling changes the XWindow position
    * and makes the child widgets appear to scroll even
    * though when queried their position is unchanged.
    * The fix is to queue a resize event for each child to
    * force the position to be corrected.
    */
    auto parentHandle = parentingHandle ();
    auto list = OS.gtk_container_get_children (parentHandle);
    if (list is null) return;
    auto temp = list;
    while (temp !is null) {
        auto widget = OS.g_list_data (temp);
        if (widget !is null) OS.gtk_widget_queue_resize  (widget);
        temp = OS.g_list_next (temp);
    }
    OS.g_list_free (list);
}

}