1534566 - Canvase throw an exception while set font

Status: NEW

(Core :: Graphics: Canvas2D, defect, P3)

Description

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Attachment: canvas.zip

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0

Steps to reproduce:

1, create index.html with the followings
<div style="display:none;">
<iframe src="./iframe.html"></iframe>
</div>
2, create iframe.html with the followings:
<canvas id="tutorial" width="0" height="0"></canvas>
<script src="./index.js">
</script>

Actual results:

"ctx.font = xxx" will throw an exception.
NS_ERROR_FAILURE:

Expected results:

no exception and font changed

Comment 1

[Andrew Osmond [:aosmond] (he/him)]

I did not see an error thrown in Chrome. We throw because:

https://searchfox.org/mozilla-central/rev/2c912888e3b7ae4baf161d98d7a01434f31830aa/dom/canvas/CanvasRenderingContext2D.h#395

mCanvasElement's mPresShell is null, so we bail with an error. I'm guessing this is because the iframe didn't trigger a reflow to create the shell since it has no contents to display.