Returns the receiver's line style, which will be one
of the constants <code>SWT.LINE_SOLID</code>, <code>SWT.LINE_DASH</code>,
<code>SWT.LINE_DOT</code>, <code>SWT.LINE_DASHDOT</code> or
<code>SWT.LINE_DASHDOTDOT</code>.
@return the style used for drawing lines
@exception SWTException <ul>
<li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
</ul>
Returns the receiver's line style, which will be one of the constants <code>SWT.LINE_SOLID</code>, <code>SWT.LINE_DASH</code>, <code>SWT.LINE_DOT</code>, <code>SWT.LINE_DASHDOT</code> or <code>SWT.LINE_DASHDOTDOT</code>.
@return the style used for drawing lines
@exception SWTException <ul> <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> </ul>