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Issue 645957 link

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Issue metadata

Status: Available
Owner: ----
Cc:
Components:
EstimatedDays: ----
NextAction: ----
OS: All
Pri: 3
Type: Bug



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Composited scrolling contents do not correctly handle CSS clips.

Project Member Reported by flackr@chromium.org, Sep 12 2016

Issue description

Version: 54.0.2816.0 (Official Build) beta (64-bit)
OS: All

What steps will reproduce the problem?
(1) Load the attached file.

What is the expected output?
Expect to see a partially clipped scroller.

What do you see instead?
See the scrolling contents paint with the clip in the current location, which is then visually incorrect when you scroll. If you select text it then paints what is now currently in the viewport.

For this reason we also cannot automatically paint backgrounds into the scrolling contents layer if clipped.

Please use labels and text to provide additional information.

 
test.html
824 bytes View Download
Summary: Composited scrolling contents do not correctly handle CSS clips. (was: Composited scrolling contents do not correctly handle clips.)
This is CSS clip that's broken, not overflow clip.
🚼😘

2016-09-12 16:47 GMT+00:00 chris… via monorail <
monorail+v2.4187517203@chromium.org>:
Project Member

Comment 3 by bugdroid1@chromium.org, Sep 13 2016

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fce29704ddbdbe670aee7a4f0a2a472930b0801b

commit fce29704ddbdbe670aee7a4f0a2a472930b0801b
Author: flackr <flackr@chromium.org>
Date: Tue Sep 13 21:45:43 2016

Don't automatically paint clipped backgrounds into scrolling contents layer.

A composited scrolling contents layer currently does not correctly handle css
clip so we only paint into the layer if you explicitly request it with local
attachment.

BUG=645957
TEST=PaintLayerScrollableAreaTest.ShouldPaintBackgroundOntoScrollingContentsLayer
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2337503002
Cr-Commit-Position: refs/heads/master@{#418379}

[modify] https://crrev.com/fce29704ddbdbe670aee7a4f0a2a472930b0801b/third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp
[modify] https://crrev.com/fce29704ddbdbe670aee7a4f0a2a472930b0801b/third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp

Comment 4 by flackr@chromium.org, Sep 14 2016

Owner: flackr@chromium.org
Status: Assigned (was: Untriaged)

Comment 5 by flackr@chromium.org, Nov 22 2016

Labels: Hotlist-Threaded-Rendering
Owner: yigu@chromium.org
Seems like we need to repaint when a composited scroller with a css clip scrolls.
Project Member

Comment 7 by bugdroid1@chromium.org, Dec 29 2016

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/141c10c87f8f4bba2d4036e1613e1d9455256c45

commit 141c10c87f8f4bba2d4036e1613e1d9455256c45
Author: yigu <yigu@chromium.org>
Date: Thu Dec 29 02:14:51 2016

Fix CSS clips cannot be correctly handled by composited scroller

BUG=645957
TEST=PaintLayerScrollableAreaTest.OnlyAutoClippedScrollingContentsLayerPromoted
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2595593002
Cr-Commit-Position: refs/heads/master@{#440925}

[modify] https://crrev.com/141c10c87f8f4bba2d4036e1613e1d9455256c45/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
[modify] https://crrev.com/141c10c87f8f4bba2d4036e1613e1d9455256c45/third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp

Comment 8 by yigu@chromium.org, Jan 4 2017

Status: Fixed (was: Assigned)

Comment 9 by flackr@chromium.org, Jan 11 2017

Cc: chrishtr@chromium.org
Status: Assigned (was: Fixed)
Looks like #7 disables composited scrolling when we have a clip but we should keep this bug open for fixing clips on composited scrolling contents if this is feasible.
Labels: -Hotlist-Threaded-Rendering Hotlist-ThreadedRendering
Owner: ----
Status: Available (was: Assigned)
Remove self from owner as I've no plan working on this bug in the near future.

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