Create a canvas or returns the one that already exists for a given element.
It first checks if the element has a canvas, if not it creates one and returns it.
The canvas is updated for:
width/height in screen pixels to completely cover the div element
CSS width/height in CSS pixels to be the size of the physical screen pixels
width and height (from #1)
This allows drawing to the canvas and having pixel perfect/exact drawing to
the physical screen pixels.
Create a canvas or returns the one that already exists for a given element. It first checks if the element has a canvas, if not it creates one and returns it. The canvas is updated for: