Bug 65276 [Preferences] Preference dialog should disable OK when okPressed
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/PreferenceDialog.java
/**
	 * Create the layout data for the message area.
	 * 
	 * @return FormData for the message area.
	 */
	private FormData createMessageAreaData() {
		FormData messageData = new FormData();
		messageData.top = new FormAttachment(0);
		messageData.bottom = new FormAttachment(titleImage, 0, SWT.BOTTOM);
		messageData.right = new FormAttachment(titleImage, 0);
		messageData.left = new FormAttachment(0);
		return messageData;
	}
	/**
	 * @param parent
	 *            the SWT parent for the tree area controls.
	 * @return the new <code>Control</code>.
	 * @since 3.0
	 */
	protected Control createTreeAreaContents(Composite parent) {
		
		treeViewer = createTreeViewer(parent);
		treeViewer.setInput(getPreferenceManager());
		updateTreeFont(JFaceResources.getDialogFont());
		layoutTreeAreaControl(treeViewer.getControl());
		return treeViewer.getControl();
	}
	/**
	 * Create a new <code>TreeViewer</code>.
	 *