The darkness value to use for grayed images. The gray image used when button is down. When the mouse is clicked, reverse the 3D border and draw a dark-gray version of the image. If you move the mouse off the button while the mouse is down, abort and do not trigger the action. Draws the image with the border around it.
Light grays look best.
Draws the image with the border around it. When the mouse is clicked, reverse the 3D border and draw a dark-gray version of the image. The action is not triggered until mouseUp. Otherwise ignore this. Override this in subclasses to give behavior to the button.