It is cross plattform.
It is just not supported at the moment to use OS gadgets within Canvas.
For event handling reasons I wouldn't do it as well because the events a canvas throws will be "blocked" by the button if it is in front of the canvas.
What do you actually try to achieve?
Because depending on what you want to achieve, I would suggest using HighGUI for fullscreen graphics (UI can't go fullscreen with graphic context, only maximized window)
It is just not supported at the moment to use OS gadgets within Canvas.
For event handling reasons I wouldn't do it as well because the events a canvas throws will be "blocked" by the button if it is in front of the canvas.
What do you actually try to achieve?
Because depending on what you want to achieve, I would suggest using HighGUI for fullscreen graphics (UI can't go fullscreen with graphic context, only maximized window)