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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - sync-layer-positions-after-scroll fails if run after non-stable-viewport-scroll due to extraneous layouts"
href="https://bugs.webkit.org/show_bug.cgi?id=168403">168403</a>
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<th>Summary</th>
<td>sync-layer-positions-after-scroll fails if run after non-stable-viewport-scroll due to extraneous layouts
</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>WebKit Nightly Build
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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
</td>
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<th>Priority</th>
<td>P2
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<th>Component</th>
<td>Tools / Tests
</td>
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>thorton@apple.com
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<th>CC</th>
<td>lforschler@apple.com
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<pre>Created <span class=""><a href="attachment.cgi?id=301685" name="attach_301685" title="logging">attachment 301685</a> <a href="attachment.cgi?id=301685&action=edit" title="logging">[details]</a></span>
logging
If you remove the viewport meta tag added to sync-layer-positions-after-scroll in <a class="bz_bug_link
bz_status_NEW "
title="NEW - WKWebView inside a UICollectionView flashes when items are inserted above it"
href="show_bug.cgi?id=168376">https://bugs.webkit.org/show_bug.cgi?id=168376</a>, and then:
run-webkit-tests -v --ios-simulator --no-retry-failures scrollingcoordinator/ios
You will see sync-layer-positions-after-scroll fail. If you run it by itself, it does not.
The attached logging is from a debugging session with smfr. For some reason, we get into a state where we are calling setViewportConstrainedObjectsNeedLayout repeatedly during scrolling with a fixedpos element, which breaks various assumptions of the test (causing the layer position to get set, and clearing the approximatePosition).
It seems like this is related to changing scale or useFlexibleViewport, or something, and smfr says he's seen it before.</pre>
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