public Insets getDockingPanelInsets() {
		// recalculate the location and size of the mouse grabber
		Insets i = new Insets(0, 0, 0, 0);
		if (topBorderPane != null && topBorderPane.isVisible()) {
			i.top += topBorderPane.getHeight();
		}
		if (leftBorderPane != null && leftBorderPane.isVisible()) {
			i.left += leftBorderPane.getWidth();
		}
		if (bottomBorderPane != null && bottomBorderPane.isVisible()) {
			i.bottom += bottomBorderPane.getHeight();
		}

		if (rightBorderPane != null && rightBorderPane.isVisible()) {
			i.right += rightBorderPane.getWidth();
		}
		return i;
	}