Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 75881e26cd3acd585ac300d8add22a1fd1c826ef
https://github.com/WebKit/WebKit/commit/75881e26cd3acd585ac300d8add22a1fd1c826ef
Author: Dana Estra <[email protected]>
Date: 2026-07-27 (Mon, 27 Jul 2026)
Changed paths:
M LayoutTests/TestExpectations
M
LayoutTests/imported/w3c/web-platform-tests/webvtt/rendering/cues-with-video/processing-model/2_cues_overlapping_partially_move_down-expected.html
M
LayoutTests/imported/w3c/web-platform-tests/webvtt/rendering/cues-with-video/processing-model/2_cues_overlapping_partially_move_down-ref.html
M Source/WebCore/rendering/RenderVTTCue.cpp
Log Message:
-----------
WebVTT cue overlap avoidance algorithm should always move cue shortest
possible distance when snap-to-lines is false
https://bugs.webkit.org/show_bug.cgi?id=320205
rdar://183151333
Reviewed by Eric Carlson.
The WebVTT positioning algorithm (7.2. Processing cue settings, step 10) asks
that
when the snap-to-lines flag is false and a cue is overlapped with another, the
renderer moves the cue in the direction (up or down if horizontal, left or right
if vertical) that renders it the shortest distance from its original placement
by
the VTT author.
The spec describes a different algorithm when snap-to-lines is true. In this
case, the
renderer should first try moving the cue up (or to the left if vertical), and
if the
edge of the video is hit before finding a non-overlapping position, then try
again in the
opposite direction. Hence, when snap-to-lines is true, the cue is always moved
up if there
is open space above regardless if there is a closer spot below.
WebKit's implementation of the snap-to-line == false path is incorrect because
it only tries
moving the cue down if moving it up was unsuccessful. This patch changes it to
check both
directions and to move the cue the shortest distance to avoid collision.
Also fixed bug in cues_overlapping_partially_move_down.html and marked it as
passing. The test
incorrectly treated default line alignment as "center", when the spec states it
should be "start."
* LayoutTests/TestExpectations:
* Source/WebCore/rendering/RenderVTTCue.cpp:
(WebCore::RenderVTTCue::findNonOverlappingPosition const):
*
LayoutTests/imported/w3c/web-platform-tests/webvtt/rendering/cues-with-video/processing-model/2_cues_overlapping_partially_move_down-expected.html:
*
LayoutTests/imported/w3c/web-platform-tests/webvtt/rendering/cues-with-video/processing-model/2_cues_overlapping_partially_move_down-ref.html:
Canonical link: https://commits.webkit.org/318012@main
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