Bug 283631 [CSS] ETabFolder in CTabFolder mode top/bottom keylines differ
bundles/org.eclipse.e4.ui.widgets/src/org/eclipse/e4/ui/widgets/ETabFolder.java
if (selectedIndex != -1 && selectionGradientColors != null && selectionGradientColors.length > 1 && !selectionGradientVertical) {
				drawBackground(gc, shape, true);
			} else if (selectedIndex == -1 && gradientColors != null && gradientColors.length > 1 && !gradientVertical) {
				drawBackground(gc, shape, false);
			} else {
				gc.setBackground(selectedIndex == -1 ? getBackground() : selectionBackground);
				gc.fillPolygon(shape);
			}
		}
		
		if ((getStyle() & SWT.NO_BACKGROUND) != 0) {
			gc.setBackground(getBackground());
			gc.fillRectangle(xClient - marginWidth, yClient - marginHeight, width, height);
		}
	} else {
		if ((getStyle() & SWT.NO_BACKGROUND) != 0) {
			int height = borderTop + tabHeight + highlight_header + borderBottom;
			if (size.y > height) {
				gc.setBackground(getParent().getBackground());
				gc.fillRectangle(0, height, size.x, size.y - height);
			}
		}
	}
	
	
	if (borderLeft > 0) {
		gc.setForeground(exteriorKeyLineColor);
		int x1 = borderLeft - 1;
		int x2 = size.x - borderRight;
		int y1 = onBottom ? borderTop - 1 : borderTop + tabHeight;