1520722 - nsColumnSetFrame's continuation is deleted due to bidi resolution

Status: RESOLVED FIXED

(Core :: Layout: Columns, defect, P3)

Description

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: bidi-column-set.html

Load the attached test case (modified from the test in bug 1516737). This needs bug 1516739 fixed, or it crashes immediately.

Expected result:
The page should render some text like "ltr".

Actual result:
The page is blank, and there are some warnings like

[2064, Main Thread] ###!!! ASSERTION: frame tree not empty, but caller reported complete status: 'aSubtreeRoot->GetPrevInFlow()', file /home/aethanyc/Projects/gecko-dev/layout/base/nsLayoutUtils.cpp, line 7480
[2064, Main Thread] ###!!! ASSERTION: frame tree not empty, but caller reported complete status: 'start == end || IsInLetterFrame(aSubtreeRoot)', file /home/aethanyc/Projects/gecko-dev/layout/base/nsLayoutUtils.cpp, line 7494

When loading the test by GECKO_FRAMECTOR_DEBUG_FLAGS=really-noisy-content-updates ./mach run, I notice that the full frame tree was constructed correctly, but later the nsColumnSetFrame's continuation is somehow being deleted due to some bidi resolution.

Comment 1

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: frame-tree-and-callstack.txt

The callstack shows that the nsColumnSetFrame (0x7f473c883698) after a -moz-column-span-wrapper is being converted from non-fluid continuation into a fluid continuation.

Comment 2

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1520722 Part 1 - Remove NS_BLOCK_NEEDS_BIDI_RESOLUTION flag from ColumnSpanWrapperFrame.

Calling nsBlockFrame::ResolveBidi() on ColumnSpanWrapperFrame may cause
nsColumnSetFrame's non-fluid continuations being converted into fluid
ones in JoinInlineAncestors().

Since ColumnSpanWrapperFrame can only have nsColumnSetFrame and
column-span wrappers kids, no need to perform bidi resolution. This
doesn't affect column contents because they'll inherit "unicode-bidi"
from ColumnSetWrapperFrame in ua.css.

Comment 3

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1520722 Part 2 - When removing bidi continuations, go no further than the block which needs resolution.

When doing bidi resolution for column-content blocks, we may still
traverse the parent chain up in RemoveBidiContinuation, reach
nsColumnSetFrame, and accidentally convert nsColumnSetFrame's
continuation into fluid ones.

Depends on D17550

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/506261cc5d79
Part 1 - Remove NS_BLOCK_NEEDS_BIDI_RESOLUTION flag from ColumnSpanWrapperFrame. r=dbaron
https://hg.mozilla.org/integration/autoland/rev/1617ad03a14e
Part 2 - When removing bidi continuations, go no further than the block which needs resolution. r=dbaron

Comment 10

[Oana Pop-Rus]

https://hg.mozilla.org/mozilla-central/rev/506261cc5d79
https://hg.mozilla.org/mozilla-central/rev/1617ad03a14e

Comment 11

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/15223 for changes under testing/web-platform/tests