As thisisnotmikey said, you can check the size of the data and see if its 42 bytes, however this also doesn't work because anytime you use the eraser, it adds to the data size. So even if you have a blank canvas and only use the erase, the data size will ballon.
canvasView.drawing.strokes.isEmpty seems to work well. So does canvasView == CGRect(origin: CGPoint(x: CGFloat.infinity, y: CGFloat.infinity), size: .zero).
Topic:
App & System Services
SubTopic:
General
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