1391841 - Clip fallback display items using WebRender clips instead of doing the clip internally

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, enhancement)

Description

[Jeff Muizelaar [:jrmuizel]]

https://bugzilla.mozilla.org/show_bug.cgi?id=1377571#c15

"It would be nice if we could always paint the entire item into the blob (and have the blob image's bounds be the whole, unclipped item), and then apply the clip on the outside."

Comment 1

[Jeff Muizelaar [:jrmuizel]]

Attachment: Do fallback display item clipping with webrender. r=ethlin

This gives a huge performance improvement when scrolling mozilla.org
However, it can cause us to make very big display items. This should
be resolved with the tiling support from bug 1387550.

Comment 2

[Ethan Lin[:ethlin]]

Comment on attachment 8899137 [details] [diff] [review]
Do fallback display item clipping with webrender. r=ethlin

Review of attachment 8899137 [details] [diff] [review]:
-----------------------------------------------------------------

The reason of using clippedBounds was because some large display items could cause crash. Some of the display items are really too large. I'm not sure how the tiled blob image works, but we probably should skip painting the tiles those are out of screen. 
I'm also worried that the change may cause some try server failures in layers-free mode while the blob image is off by default and I'm trying to turn on layers-free. How about just doing the clipping for non-blobimage? e.g.:

  if (!gfxPrefs::WebRenderBlobImages() && clip.HasClip()) {
    clippedBounds = itemBounds.Intersect(clip.GetClipRect());
  }

::: gfx/layers/wr/WebRenderLayerManager.cpp
@@ +434,2 @@
>    aOffset = ViewAs<LayerPixel>(
> +      LayoutDevicePoint::FromAppUnits(aItem->ToReferenceFrame(), appUnitsPerDevPixel),

I fixed a position problem. So the latest code is "LayoutDevicePoint::FromAppUnits(clippedBounds.TopLeft(), appUnitsPerDevPixel)". I think for this patch we should use itemBounds.TopLeft() here.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/dfade36563b4
Clip fallback display items using WebRender clips instead of doing the clip internally. r=ethlin

Comment 4

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/dfade36563b4