Bug 249915 [Dialogs] TitleAreaDialog does not short circuit if message is null
M20080911-1700 When profiling use of a custom WizardDialog on Linux/GTK, a lot of time was spent in WizardPage.setMessage(...). It turns out that this was because we were setting a message of null after each keypress, and the page's description (DialogPage.getDescription()) was also null. In this case the short-circuit in TitleAreaDialog.setMessage(String, int) fails to notice that the message has not changed, and does a layout every time. For our dialog this takes about 40ms each time, which is noticeable when compounded with other work.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/TitleAreaDialog.java
}
	/**
	 * Make the label used for displaying error images visible depending on
	 * boolean.
	 * 
	 * @param visible
	 *            If <code>true</code> make the image visible, if not then
	 *            make it not visible.
	 */
	private void setImageLabelVisible(boolean visible) {
		messageImageLabel.setVisible(visible);
		bottomFillerLabel.setVisible(visible);
		leftFillerLabel.setVisible(visible);
	}
	/**
	 * Reset the attachment of the workArea to now attach to top as the top
	 * control.
	 * 
	 * @param top
	 */
	private void resetWorkAreaAttachments(Control top) {
		FormData childData = new FormData();
		childData.top = new FormAttachment(top);
		childData.right = new FormAttachment(100, 0);
		childData.left = new FormAttachment(0, 0);
		childData.bottom = new FormAttachment(100, 0);
		workArea.setLayoutData(childData);
	}
}