Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 9d3c89bfe30cee221fa647c3599cc8b0d033fbd5
https://github.com/WebKit/WebKit/commit/9d3c89bfe30cee221fa647c3599cc8b0d033fbd5
Author: Alan Baradlay <[email protected]>
Date: 2023-05-26 (Fri, 26 May 2023)
Changed paths:
M
Source/WebCore/layout/formattingContexts/inline/InlineFormattingGeometry.cpp
Log Message:
-----------
[IFC][Float] Incorrectly placed float boxes may generate series of empty lines
https://bugs.webkit.org/show_bug.cgi?id=257261
<rdar://108742128>
Reviewed by Antti Koivisto.
When intrusive floats prevent us from placing any content at the current
vertical position,
the candidate position for the next line is computed by looking at such
intrusive floats.
e.g.
Two float boxes with the inline content of "foobar".
_______ _______
| | | |
| left | | right |
|_______| | |
|_______|
1. "foobar" does not fit at y: 0 (overlaps "left").
2. we find 2 intrusive floats at y: 0
3. vertical position for next line is at the bottom of "left1"
This is rather simple, but if float placement bugs produce some vertical gaps
between floats
e.g.
_______ _______
| | | |
| left1 | | right |
|_______| | |
|_______|
_______
| |
| left2 |
|_______|
(note that left2 is supposed to be vertically adjacent to left1)
Now if we run line layout:
1. "foobar" does not fit at y: 0 -> vertical position for next line is at the
bottom of "left1"
2. "foobar" still does not fit (assume it overlaps "right") -> position for
next line is at the bottom of "right"
3. now assume that "foobar" is tall and it does not fit between the bottom of
the "right" and the top of this incorrectly placed "left2"
_______ _______
| | | |
| left1 | | right |
|_______| | |
|_______|
____
|
|___
_|_____
| | |
| | |
|_______|
running "let's find the position for next line by avoiding intrusive floats"
logic in InlineFormattingGeometry::logicalTopForNextLine()
finds no intrusive float at the bottom of the "right" float (that's what #2
computed as candidate position).
This is an unexpected state (we assert) and in order not to get stuck on the
same vertical position we advance by 1px for the next line hoping we would be
able to place "foobar" there.
While it helps to avoid forever looping, if the gap between the bottom of the
"right" and the top of the "left2" is
wide we may end up producing thousands of empty lines until we reach the top
of the "left2" float box and finally get out of this unexpected state.
In this patch, instead of advancing by 1px, we jump right to the bottom of the
"left2" float box (bottom of all the floats in this floating context) and
continue from there.
* Source/WebCore/layout/formattingContexts/inline/InlineFormattingGeometry.cpp:
(WebCore::Layout::InlineFormattingGeometry::logicalTopForNextLine const): move
float handling to a helper (intrusiveFloatBottom) and return
the max of floatingContext.bottom() and lineLogicalRect.bottom().
Canonical link: https://commits.webkit.org/264579@main
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