void drawMouseOverCorners (Graphics& g, int w, int h)
{
    RectangleList r (Rectangle<int> (0, 0, w, h));
    r.subtract (Rectangle<int> (1, 1, w - 2, h - 2));

    const int size = jmin (w / 3, h / 3, 12);
    r.subtract (Rectangle<int> (size, 0, w - size - size, h));
    r.subtract (Rectangle<int> (0, size, w, h - size - size));

    g.setColour (Colours::darkgrey);

    for (int i = r.getNumRectangles(); --i >= 0;)
        g.fillRect (r.getRectangle (i));
}