Bug 63420 [R21PRES] Flash on tab switch
bundles/org.eclipse.ui.presentations.r21/src/org/eclipse/ui/internal/presentations/R21EditorStackPresentation.java
bgPercents = R21Colors.getDeactivatedEditorGradientPercents();
			}
		} else if (activeState == AS_ACTIVE_NOFOCUS) {
			fgColor = R21Colors.getSystemColor(SWT.COLOR_LIST_FOREGROUND);
			bgColors = R21Colors.getActiveNoFocusEditorGradient();
			bgPercents = R21Colors.getActiveNoFocusEditorGradientPercents();
		} else {
			fgColor = null;
			bgColors = null;
			bgPercents = null;
		}
		drawGradient(fgColor, bgColors, bgPercents, vertical);
	}
	/**
	 * Sets the gradient for the selected tab
	 * 
	 * @param fgColor
	 * @param bgColors
	 * @param percentages
	 * @param vertical
	 */
	protected void drawGradient(Color fgColor, Color[] bgColors,
			int[] percentages, boolean vertical) {
		tabFolder.setSelectionForeground(fgColor);
		tabFolder.setSelectionBackground(bgColors, percentages);
		tabFolder.update();
	}
	/**
	 * Return whether the window's shell is activated
	 */