1201937 - 1143303-1.svg renders incorrectly in reftests with DrawTargetTiled enabled

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[James Willcox (:snorp) ([e-mail]) (he/him)]

I don't know why. It looks fine if I simply view it with Fennec.

Comment 1

[Lee Salzman [:lsalzman]]

Attachment: push transform onto cairo context when evaluating path bounds

The problem arises in DrawTargetTiled::Fill(), with respect to this reftest. The reftest draws a really small circle, small enough that it will not fit in cairo's fixed-point coordinate type without rounding down to 0.

So 0 bounds are what cairo_path_extents() returns to us, before we apply the transform that would scale it up to be large enough to span multiple tiles. But since the bounds are "empty", the transform can no longer help.

So when DrawTargetTiled is trying to get the path bounds, then determine which tiles intersect the path bounds, it sees the empty rectangle and decides the circle intersects no titles.

The only way around this is to push the transform onto the cairo context before we set the path on it, so that it is scaled up properly before it ever gets transformed to fixed point, which is what this patch to PathCairo does.

Comment 2

[Lee Salzman [:lsalzman]]

This bug might also be the cause of the issue noted in bug 1204076, so we should investigate if that is a dup...

Comment 3

[Lee Salzman [:lsalzman]]

Attachment: push transform onto cairo context when evaluating path bounds

Revised version of the patch to properly handle stroke line widths.

Line widths are effectively interpreted in the space of the transform when we do bounds or contains queries, so the transform must still be active on the context at the time we do this. Thus, resetting the transform to identity was breaking stroke queries.

So, this version of the patch just keeps the parts of the original patch that set the transform, but removes the other parts that were resetting to identity space.

Comment 4

[Lee Salzman [:lsalzman]]

Try results: https://treeherder.mozilla.org/#/jobs?repo=try&revision=b5a92e89c35e

Comment 5

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/cd3176041896

Comment 6

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/cd3176041896