set-canvas-background in canvas<%>

Sets the color used to ``erase'' the canvas content before on-paint is called. (This color is typically associated with the canvas at a low level, so that it is used even when a complete refresh of the canvas is delayed by other activity.)

If the canvas was created with the 'transparent style, an exn:fail:contract exception is raised.

• (send a-canvas set-canvas-background color) -> void
     color : color% object

  Sets the canvas's background.