anywidget in vscode: snapshot stays pending when canvas isn't visible #218

I am on my laptop at the moment, So my screen is only 1080 pixels tall. When I tried the example notebook I noticed something odd:

if the canvas is not visible, the screenshot remains pending. So if you never let a cell output the canvas, screenshot remains pending. But also if you scroll the screenshot out of the view. I tried to read the code a bit or even debug step it. I saw there was even logic for this exact case.

But it seems like we never get there in the first place. _maybe_draw never gets reached, because _shedule_maybe_draw never gets reached but _rc_request_draw seems to only get reached when the canvas is running... so I looked into the self.request_draw() situation and that said it sets a flag that only works in "ondemand" mode.

so I tried that update mode and now the snapshots is response, even without a canvas in view. But not if you never let the canvas display in the first case (while a closed canvas is okay...).

So something in the timeline is not working out. Perhaps it would be okay to but a _shedule_maybe_draw at the end of .snapshot?