There seems to be some glitch concerning the Canvas object that I think involves using "Grab Layout Before Drawing". I can choose to have the game fullscreen through the Application properties and it works just fine, but when I have a key (in this case Enter) to SWITCH to fullscreen the image just becomes garbled. If an event is added to clear the canvas to transparent upon pressing Enter I don't get a garbled image, but it is instead frozen. If I always have it clear to transparent I can't use the Canvas Object as an all-covering effect (in lack of Layer Effect changing during runtime, I am using a canvas).
In the attached file the canvas is making the screen greyscale. Pressing Enter will switch to fullscreen.
Fullscreen glitch concerning Canvas
For some ungodly reason the CAP doesn't want to open in Construct and no matter how I try to downsize the CAP it always ends up a broken file.
It might work for you though, my computer is being weird with that one CAP-file.