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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Implement WebVTT VTTCue lineAlign and positionAlign attributes"
href="https://bugs.webkit.org/show_bug.cgi?id=168715">168715</a>
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<th>Summary</th>
<td>Implement WebVTT VTTCue lineAlign and positionAlign attributes
</td>
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<th>Classification</th>
<td>Unclassified
</td>
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<th>Product</th>
<td>WebKit
</td>
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<th>Version</th>
<td>Safari Technology Preview
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<th>Hardware</th>
<td>Unspecified
</td>
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<th>OS</th>
<td>Unspecified
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>Normal
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<th>Priority</th>
<td>P2
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<th>Component</th>
<td>Media Elements
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>zcorpan@gmail.com
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<pre>VTTCue.lineAlign and VTTCue.positionAlign are not supported.
In the WebVTT syntax these are specified after a "," in position and line settings.
Spec:
<a href="http://w3c.github.io/webvtt/#webvtt-cue-position-alignment">http://w3c.github.io/webvtt/#webvtt-cue-position-alignment</a>
<a href="http://w3c.github.io/webvtt/#webvtt-cue-line-alignment">http://w3c.github.io/webvtt/#webvtt-cue-line-alignment</a>
<a href="http://w3c.github.io/webvtt/#parse-the-webvtt-cue-settings">http://w3c.github.io/webvtt/#parse-the-webvtt-cue-settings</a>
<a href="http://w3c.github.io/webvtt/#the-vttcue-interface">http://w3c.github.io/webvtt/#the-vttcue-interface</a>
Tests:
<a href="http://w3c-test.org/webvtt/api/VTTCue/lineAlign.html">http://w3c-test.org/webvtt/api/VTTCue/lineAlign.html</a>
<a href="http://w3c-test.org/webvtt/api/VTTCue/positionAlign.html">http://w3c-test.org/webvtt/api/VTTCue/positionAlign.html</a>
These are supported in Gecko. Bug for Chromium: <a href="https://bugs.chromium.org/p/chromium/issues/detail?id=633690">https://bugs.chromium.org/p/chromium/issues/detail?id=633690</a>
I think the use case is basically better control in positioning things.
See <a href="http://w3c.github.io/webvtt/#example-0c2976c9">http://w3c.github.io/webvtt/#example-0c2976c9</a> for an example.
00:00:00.000 --> 00:00:04.000 position:10%,line-left align:left size:35%
Where did he go?
Without position-align you need to set position to some value that doesn't correspond to what the author actually intends:
00:00:00.000 --> 00:00:04.000 position:27.5% align:left size:35%
Where did he go?
27.5% here is: intended position (10%) + size/2 (35%/2). Not intuitive.
Having this also makes the mapping from other subtitle formats to WebVTT (and back) more straightforward.</pre>
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