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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [Threaded Compositor] Move the viewport controller off the compositing thread"
href="https://bugs.webkit.org/show_bug.cgi?id=161532">161532</a>
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<th>Summary</th>
<td>[Threaded Compositor] Move the viewport controller off the compositing thread
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<th>Classification</th>
<td>Unclassified
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<th>Product</th>
<td>WebKit
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<th>Version</th>
<td>WebKit Local Build
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<th>Hardware</th>
<td>Unspecified
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<th>OS</th>
<td>Unspecified
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<th>Status</th>
<td>NEW
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<th>Keywords</th>
<td>Gtk
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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>WebKit2
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>cgarcia@igalia.com
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<th>CC</th>
<td>bugs-noreply@webkitgtk.org
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<pre>While working on <a class="bz_bug_link
bz_status_NEW "
title="NEW - [GTK][Threaded Compositor] Several flaky tests"
href="show_bug.cgi?id=161242">bug #161242</a> I've realized that having the view port controller in the compositing thread makes everything more complex. The viewport controller receives changes about things like contents size, viewport size, etc. and uses that information to compute the visible contents rect and page scale factor. Then it notifies back to main thread about the computed visible contents rect and page scale. Those computations are not heave at all, so they could be done in the main thread and we would avoid communications between the main and compositing thread in both directions. The main thread needs the visible contents rect to notify the compositing coordinator and the page cale to scale the page in case of pixed layout. But the compositing thread only needs to know the effective scale and scroll position. So, instead of going to the compositing thread after every change that might update the visible contents rect and page scale factor, we could do those calcul
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