Bug 317180 Screen cheese when starting fresh workspace
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/CTabRendering.java
points[index++] = circY - radius;
		int[] tempPoints = new int[index];
		System.arraycopy(points, 0, tempPoints, 0, index);
		shape = tempPoints;
		gc.fillPolygon(shape);
		
		Region r = new Region();
		r.add(bounds);
		r.subtract(shape);
		gc.setBackground(parent.getParent().getBackground());
		Display display = parent.getDisplay();
		Region clipping = new Region();
		gc.getClipping(clipping);
		r.intersect(clipping);
		gc.setClipping(r);
		Rectangle mappedBounds = display
				.map(parent, parent.getParent(), bounds);
		parent.getParent().drawBackground(gc, bounds.x, bounds.y, bounds.width,
				bounds.height, mappedBounds.x, mappedBounds.y);
		
		if (shadowEnabled)
			drawShadow(display, bounds, gc);
		gc.setClipping(clipping);
		clipping.dispose();
		r.dispose();
	}
	void drawSelectedTab(int itemIndex, GC gc, Rectangle bounds, int state) {
		int width = bounds.width;
		int[] points = new int[1024];
		int index = 0;