Bug 56637 [Preferences] DialogMessageArea image is too large
Is the background color of the error shown by DialogMessageArea to be changed? Or do you intend to leave it as it is right now? The error message looks a little out of place in the current implementation (being surrounded by white space).
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/PreferenceDialog.java
* sets the window's return code to <code>CANCEL</code>
	 * and closes the window using <code>close</code>.
	 * Subclasses may extend or reimplement.
	 * </p>
	 */
	protected void handleShellCloseEvent() {
		
		cancelPressed();
	}
	/**
	 * Notifies of the pressing of the Help button.
	 * <p>
	 * The default implementation of this framework method
	 * calls <code>performHelp</code> on the currently active page.
	 * </p>
	 */
	protected void helpPressed() {
		if (currentPage != null) {
			currentPage.performHelp();
		}
	}
	/**
	 * Returns whether the current page is valid.
	 *
	 * @return <code>false</code> if the current page is not valid, or
	 *  or <code>true</code> if the current page is valid or there is
	 *  no current page
	*/
	protected boolean isCurrentPageValid() {
		if (currentPage == null)