Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: c2b79f5f2ba7901ea4cdf02743c178b61270451b
https://github.com/WebKit/WebKit/commit/c2b79f5f2ba7901ea4cdf02743c178b61270451b
Author: Jer Noble <[email protected]>
Date: 2024-01-12 (Fri, 12 Jan 2024)
Changed paths:
A LayoutTests/media/content/test-paint-on-captions.mp4
A LayoutTests/media/track/track-paint-on-captions-expected.txt
A LayoutTests/media/track/track-paint-on-captions.html
M LayoutTests/platform/glib/TestExpectations
M
Source/WebCore/platform/graphics/avfoundation/InbandTextTrackPrivateAVF.cpp
Log Message:
-----------
REGRESSION(271415@main): Paint-on captions shift slightly during playback
https://bugs.webkit.org/show_bug.cgi?id=267413
rdar://120847946
Reviewed by Eric Carlson.
When AVFoundation parses CEA-609 captions and provides them to WebKit via an
NSAttributedString,
that string will have it's kCMTextMarkupAttribute_Alignment property set to
kCMTextMarkupAlignmentType_Middle, unless the cue is multiple lines, the lines
are different
lengths, and those lines visually align on the left or right. WebKit in turn
sets the
InbandTextTrackCue's positionAlign and position properties to be centered.
However for
paint-on captions, differences in the font metrics between AVFoundation and
WebKit cause the
text to visually shift on the screen as the cue "grows" in length.
When we receive inband cue data that indicates a "middle" alignment, ignore
that alignment for
the purposes of positioning the cue within the video's viewport, and treat the
cue as if it was
aligned to the left. "Middle" aligned cues with multiple lines will still be
centered within the
cue box, however.
* LayoutTests/media/content/test-paint-on-captions.mp4: Added.
* LayoutTests/media/track/track-paint-on-captions-expected.txt: Added.
* LayoutTests/media/track/track-paint-on-captions.html: Added.
* Source/WebCore/platform/graphics/avfoundation/InbandTextTrackPrivateAVF.cpp:
(WebCore::InbandTextTrackPrivateAVF::processCueAttributes):
Canonical link: https://commits.webkit.org/272966@main
_______________________________________________
webkit-changes mailing list
[email protected]
https://lists.webkit.org/mailman/listinfo/webkit-changes
