Bug 63420 [R21PRES] Flash on tab switch
bundles/org.eclipse.ui.presentations.r21/src/org/eclipse/ui/internal/presentations/R21EditorStackPresentation.java
Point localPos = tabFolder.toControl(location);
		final CTabItem tabUnderPointer = tabFolder.getItem(localPos);
		
		
		if (tabUnderPointer == null)
			return null;
		
		int dragOverIndex = tabFolder.indexOf(tabUnderPointer);
		return new StackDropResult(Geometry.toDisplay(tabFolder,
				tabUnderPointer.getBounds()), new Integer(dragOverIndex));
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.presentations.StackPresentation#showSystemMenu()
	 */
	public void showSystemMenu() {
		if (null != current) {
			
			CTabItem item = getTab(current);
			getSite().selectPart(getCurrentPart());
			Rectangle bounds = item.getBounds();
			int y = bounds.height;
			if (getTabFolder().getTabPosition() == SWT.BOTTOM)
				y += bounds.y;
			showSystemMenu(getTabFolder().toDisplay(bounds.x, y));
		}
	}
	/*