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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - preserveDrawingBuffer=true wrongly double-buffers on current iOS h/w"
href="https://bugs.webkit.org/show_bug.cgi?id=159608">159608</a>
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<th>Summary</th>
<td>preserveDrawingBuffer=true wrongly double-buffers on current iOS h/w
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr>
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<th>Product</th>
<td>WebKit
</td>
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<th>Version</th>
<td>Other
</td>
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<th>Hardware</th>
<td>iOS
</td>
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<th>OS</th>
<td>iOS 9.2
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>Normal
</td>
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<th>Priority</th>
<td>P2
</td>
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<th>Component</th>
<td>WebGL
</td>
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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</tr>
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<th>Reporter</th>
<td>reuben.scratton@gmail.com
</td>
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<th>CC</th>
<td>dino@apple.com
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<p>
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<pre>[F.A.O. Dean Jackson]
Using preserveDrawingBuffer=true on iOS wrongly expects that rendering is done to two alternating backbuffers, i.e. normal double-buffering. As far as I can tell other WebGL implementations treat preserveDrawingBuffer=true as rendering to a single backbuffer which is then copied to the front buffer rather than swapped.
Here is a simple demo of preserveDrawingBuffer=true written by Gregg Tavares:
<a href="http://greggman.com/downloads/examples/webgl/lessons/resources/webgl-preservedrawingbuffer-true.html">http://greggman.com/downloads/examples/webgl/lessons/resources/webgl-preservedrawingbuffer-true.html</a>
This demo looks fine on all desktop browsers and Android but flickers dreadfully on mobile Safari on iOS 9.x and 8.x because of the unexpected double-buffering.
I reported the issue to Gregg and he advised me to report it here, marked for the attention of Dean.</pre>
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