Bug 283631 [CSS] ETabFolder in CTabFolder mode top/bottom keylines differ
bundles/org.eclipse.e4.ui.widgets/src/org/eclipse/e4/ui/widgets/ETabItem.java
shape[index++] = y + height;
	return shape;
}
void drawUnselectedBorder(GC gc, int shape[]) {
	Color borderColor = getETabParent().interiorKeyLineColor;
	gc.setForeground(borderColor);
	gc.drawPolyline(shape);
}
int preferredHeight(GC gc) {
	
	if(! getETabParent().webbyStyle || this.parent.onBottom || parent.single) {
		return super.preferredHeight(gc);
	}
	Image image = getImage();
	int h = (image == null) ? 0 : image.getBounds().height;
	String text = getText();
	if (font == null) {
		h = Math.max(h, gc.textExtent(text, FLAGS).y);
	} else {
		Font gcFont = gc.getFont();
		gc.setFont(font);
		h = Math.max(h, gc.textExtent(text, FLAGS).y);
		gc.setFont(gcFont);
	}
	int prefHeight = h
		+ getETabParent().tabTopMargin
		+ getETabParent().topMargin
		+ getETabParent().selectionMargin
		+ getETabParent().tabBottomMargin;