CanvasView and clear_rect

[JeremiasE]

Clearing a rectangle is not visible in previous views of the widget. To be more precise construct a canvas widget and show it:

from ipycanvas import Canvas  
canvas = Canvas(size=(200, 200))  
canvas.fill_rect(0,0,100,100)  
canvas  

Now clear a rectangle:

canvas.clear_rect(0,0,20,20)

This does not result in a change of the visible canvas widget.
Showing another instance of the widget by putting

canvas

in a new cell shows the cleared rectangle however.

Is this intentional?

It seems to be due to the fact that the views are updated by drawing the model canvas on them, but clearing a rectangle makes it transparent. Putting this.clear() before
the call to drawImage in updateCanvas fixes this for me.

[martinRenou]

I am surprised I did not see this! Thanks a lot :)

Indeed calling this.clear before updating the view with drawImage should fix this. Do you want to open a PR so you get credits for your fix?

[JeremiasE]

I opened #60. I was afraid that clearing the canvas would result in flickering animations but at least in the game of life example I didn't notice anything.

[martinRenou]

Thanks a lot! I was also afraid of the flickering at first but I suppose it will be fine.

[martinRenou]

Fixed by #60

[martinRenou]

0.4.1 with your fix released on PyPi :) Coming soon on conda