1149260 - PresShell::PaintRangePaintInfo can request a zero-height surface from gfx

Status: RESOLVED FIXED

(Core :: Layout, defect)

Description

[Kartikaya Gupta (email:[e-mail])]

Attachment: lldb backtrace

While attempting to run the browser/base/content/test/newtab/browser_newtab_drag_drop.js mochitest locally on OS X I keep hitting a gfxCriticalError being logged from the gfx code. Stack attached. I do have some local changes but they shouldn't affect this code path. When the PresShell::PaintRangePaintInfo function is called with aArea = nsRect(0, 47640, 64800, 60) and maxSize is computed as nsRect(0, 1320, 86400, 52440) then the pixelArea needs resizing because it's too wide. The scale factor computed is 0.666 and so the pixelArea gets scaled down to have a height of 0. Seems like the PaintRangePaintInfo should detect this and guard against it?

Comment 1

[Kartikaya Gupta (email:[e-mail])]

Attachment: Workaround

Comment 2

[Kartikaya Gupta (email:[e-mail])]

I don't know who owns/knows this code, looks like it's been largely untouched since it was added by Neil 8 years ago except for large refactoring-type changes.

Applying the workaround in comment 1 fixes the gfxCriticalError I was seeing, but that test is still causing issues for me and I'm not sure if it's because the workaround is bad or if there are other differences between my local setup and tryserver (or both). If somebody who knows this code can validate/review my workaround it would help.

Comment 3

[Neil Deakin]

The code you are citing is used to draw the drag feedback image. Your example suggests that the test is trying to drag something that is 1080 x 1 pixels in size, which can't really be scaled down. The options here would be to crop instead, or just return null to have no feedback. On Mac, this will default to a small rectangle if I remember correctly.
So I think your patch here should be ok.

You probably also want to adjust the similar code in nsBaseDragService::DrawDragForImage though, which is used specifically when dragging image elements.

Comment 4

[Kartikaya Gupta (email:[e-mail])]

Attachment: Patch

Thanks for the info!

Comment 5

[Kartikaya Gupta (email:[e-mail])]

Try https://treeherder.mozilla.org/#/jobs?repo=try&revision=d244b7c68be6 includes this change and looks green.

Landed: https://hg.mozilla.org/integration/mozilla-inbound/rev/c236d0f0e428

Comment 6

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/c236d0f0e428