FormLayout

Instances of this class control the position and size of the children of a composite control by using <code>FormAttachments</code> to optionally configure the left, top, right and bottom edges of each child. The following example code creates a <code>FormLayout</code> and then sets it into a <code>Shell</code>: <pre> Display display = new Display (); Shell shell = new Shell(display); FormLayout layout = new FormLayout(); layout.marginWidth = 3; layout.marginHeight = 3; shell.setLayout(layout); </pre> To use a <code>FormLayout</code>, create a <code>FormData</code> with <code>FormAttachment</code> for each child of <code>Composite</code>. The following example code attaches <code>button1</code> to the top and left edge of the composite and <code>button2</code> to the right edge of <code>button1</code> and the top and right edges of the composite: <pre> FormData data1 = new FormData(); data1.left = new FormAttachment(0, 0); data1.top = new FormAttachment(0, 0); button1.setLayoutData(data1); FormData data2 = new FormData(); data2.left = new FormAttachment(button1); data2.top = new FormAttachment(0, 0); data2.right = new FormAttachment(100, 0); button2.setLayoutData(data2); </pre> Each side of a child control can be attached to a position in the parent composite, or to other controls within the <code>Composite</code> by creating instances of <code>FormAttachment</code> and setting them into the top, bottom, left, and right fields of the child's <code>FormData</code>. If a side is not given an attachment, it is defined as not being attached to anything, causing the child to remain at its preferred size. If a child is given no attachment on either the left or the right or top or bottom, it is automatically attached to the left and top of the composite respectively. The following code positions <code>button1</code> and <code>button2</code> but relies on default attachments: <pre> FormData data2 = new FormData(); data2.left = new FormAttachment(button1); data2.right = new FormAttachment(100, 0); button2.setLayoutData(data2); </pre> IMPORTANT: Do not define circular attachments. For example, do not attach the right edge of <code>button1</code> to the left edge of <code>button2</code> and then attach the left edge of <code>button2</code> to the right edge of <code>button1</code>. This will over constrain the layout, causing undefined behavior. The algorithm will terminate, but the results are undefined.

@see FormData @see FormAttachment @see <a href="http://www.eclipse.org/swt/snippets/#formlayout">FormLayout snippets</a> @see <a href="http://www.eclipse.org/swt/examples.php">SWT Example: LayoutExample</a> @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>

@since 2.0

final

class FormLayout : Layout {

this();

String toString();

}

Constructors

this this(): Constructs a new instance of this class.

Members

Functions

toString String toString(): Returns a string containing a concise, human-readable description of the receiver.

Variables

marginBottom int marginBottom;: marginBottom specifies the number of pixels of vertical margin that will be placed along the bottom edge of the layout.
marginHeight int marginHeight;: marginHeight specifies the number of pixels of vertical margin that will be placed along the top and bottom edges of the layout.
marginLeft int marginLeft;: marginLeft specifies the number of pixels of horizontal margin that will be placed along the left edge of the layout.
marginRight int marginRight;: marginRight specifies the number of pixels of horizontal margin that will be placed along the right edge of the layout.
marginTop int marginTop;: marginTop specifies the number of pixels of vertical margin that will be placed along the top edge of the layout.
marginWidth int marginWidth;: marginWidth specifies the number of pixels of horizontal margin that will be placed along the left and right edges of the layout.
spacing int spacing;: spacing specifies the number of pixels between the edge of one control and the edge of its neighbouring control.

Inherited Members

From Layout

computeSize Point computeSize(Composite composite, int wHint, int hHint, bool flushCache): Computes and returns the size of the specified composite's client area according to this layout. This method computes the size that the client area of the composite must be in order to position all children at their preferred size inside the composite according to the layout algorithm encoded by this layout. When a width or height hint is supplied, it is used to constrain the result. For example, if a width hint is provided that is less than the width of the client area, the layout may choose to wrap and increase height, clip, overlap, or otherwise constrain the children.
flushCache bool flushCache(Control control): Instruct the layout to flush any cached values associated with the control specified in the argument <code>control</code>.
layout void layout(Composite composite, bool flushCache): Lays out the children of the specified composite according to this layout. This method positions and sizes the children of a composite using the layout algorithm encoded by this layout. Children of the composite are positioned in the client area of the composite. The position of the composite is not altered by this method. When the flush cache hint is true, the layout is instructed to flush any cached values associated with the children. Typically, a layout will cache the preferred sizes of the children to avoid the expense of computing these values each time the widget is laid out. When layout is triggered explicitly by the programmer the flush cache hint is true. When layout is triggered by a resize, either caused by the programmer or by the user, the hint is false.