Canvas with fractional margin has wrong size
Categories
(Core :: Graphics: WebRender, defect, P3)
Tracking
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| Tracking | Status | |
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| firefox73 | --- | fixed |
People
(Reporter: aosmond, Assigned: aosmond)
References
(Blocks 1 open bug)
Details
Attachments
(1 file)
Before bug 1574493, I believe we passed layout/reftests/bugs/602200-3.html by fluke, rather than actually doing something correct:
The snapping code makes the primitive slightly oversized, in a way that is correct and consistent with all other primitives, but for some reason doesn't produce the expected result. This requires further investigation.
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Assignee | |
Comment 1•4 years ago
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Bug 602200 comment 36 describes this test case in more detail. The test case was created because there was a gap between the border and the canvas element. This was an accident of how the different layers would snap, not taking into account the full transform at all layers. As such, there was a bit of a hack added to snap the transforms, to position the border and the canvas flush against one another.
WebRender on the other hand, does what was described as the ideal case. It draws both the border and the canvas flush against one another, taking into account the full transform/margin information. It doesn't need to do the fudging of the transforms, but this means it is effectively shifted to the right by 1 pixel.
I think this may be a case of the test out-living its usefulness, unless we have a good explanation for why we should replicate this exact behaviour.
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Assignee | |
Comment 2•4 years ago
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Historically there were kludges in how we chose to snap layers and
transforms, nominally for performance reasons (see bug 602200 comment
36). WebRender appears to render what was considered at the time the
ideal outcome, which also makes the most sense as a content author.
Given we are otherwise lacking a reason to continue with the old
behaviour, this patch adds a new test case to confirm WebRender snaps in
the ideal fashion, and non-WebRender does not.
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Updated•4 years ago
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Assignee | |
Comment 3•4 years ago
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Pushed by aosmond@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/26d9ba863abc Add new test case to confirm WebRender snaps in the ideal fashion. r=jrmuizel
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Comment 5•4 years ago
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| bugherder | ||
Description
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