private void paintGapSelection(Graphics g, LayoutBackgroundColorManager colorManager,
			Rectangle rect, int gapIndex) {
		Color gapColor = colorManager.getPaddingColor(gapIndex);
		if (gapColor == null) {
			return;
		}
		if (gapIndex == -1) {
			gapIndex = fields.length;
		}
		int startX =
			gapIndex == 0 ? rect.x
					: fields[gapIndex - 1].getStartX() +
						fields[gapIndex - 1].getWidth();
		int endX = gapIndex >= fields.length ? rect.x + rect.width : fields[gapIndex].getStartX();

		if (startX < endX) {
			g.setColor(gapColor);
			g.fillRect(startX, -heightAbove, endX - startX, heightAbove + heightBelow);
		}
	}
Returns the row number of this layout with respect to its containing layout.
@return the row number of this layout with respect to its containing layout.
Ghidra/Framework/Docking/src/main/java/docking/widgets/fieldpanel/support/RowLayout.java