1460023 - Add a complex-area bit on CompositorHitTestInfo

Status: NEW

(Core :: Web Painting, enhancement, P5)

Description

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

For hit-testing SVGs in webrender without excessive dispatch-to-content, it would be useful to have a bit on the CompositorHitTestInfo that says "the hit area of this thing is not the same as the bounding rect". This would be set on things like SVG circle elements.

Comment 1

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

Also, we can probably use this bit instead of the NS_FRAME_SVG_LAYOUT at [1] so that not rectangular SVG frames don't end up as dispatch-to-content unnecessarily in the non-webrender codepath.

[1] https://searchfox.org/mozilla-central/rev/f30847c12e5fb13791401ed4330ced3e1b9c8d81/layout/painting/FrameLayerBuilder.cpp#3871

Comment 2

[Aria Beingessner [:Gankra]]

Attachment: Bug 1460023 - Add Complex Region flag to HitTestInfo.

Review commit: https://reviewboard.mozilla.org/r/242442/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/242442/

Comment 3

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

Comment on attachment 8974164 [details]
Bug 1460023 - Add Complex Region flag to HitTestInfo.

https://reviewboard.mozilla.org/r/242442/#review248374

LGTM, but do a try push before landing. Added miko as well since I'm not sure if this impacts retained display list building or other code paths.

Comment 4

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

Comment on attachment 8974164 [details]
Bug 1460023 - Add Complex Region flag to HitTestInfo.

Looks like we might not need this after all, it doesn't help as much as we thought it might because the enclosing SVG background item won't be part of the WR blob, and if the first thing we encounter inside the SVG is a complex region then we have to fall back to dispatch-to-content anyway. This will make the resulting stuff ordering-dependent to some extent and hard to reason about. I'll revisit this later, maybe.