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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - position:fixed and background-color lead to painting artifacts on non-retina displays"
href="https://bugs.webkit.org/show_bug.cgi?id=156817">156817</a>
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<th>Summary</th>
<td>position:fixed and background-color lead to painting artifacts on non-retina displays
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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 9
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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
</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>Layout and Rendering
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>kneebraces22@gmail.com
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<th>CC</th>
<td>simon.fraser@apple.com
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<pre>This bug is a little finicky and doesn't manifest consistently. However, the setup in this JSFiddle (<a href="https://jsfiddle.net/Lcu6Lrv9/7/">https://jsfiddle.net/Lcu6Lrv9/7/</a>) seems to reproduce it fairly reliably.
We have three dom elements: a container which is styled with 'position: fixed', a box with a background color, and a div with a background image that is scaled / positioned to be centered within our box. Often the background color of the box element that is *outside* of the bounding box of the image is colored incorrectly. The incorrect color seems to be a function of the original background color (e.g if our background color is blue the buggy color is orange). I've reproduced this using a background-image, an <img> tag, and with an inline SVG (though it seems to happen most consistently with the setup above.) I have also reproduced this bug with PNGs and SVGs so I don't think it's related to the image type. The most important aspect seems to be that the top level container element has 'positioned: fixed'.
This bug *only* manifests on non-retina displays. I have never reproduced it on a retina display. Usually opening the inspector or dragging the window around or anything that might cause a repaint causes the weird background color to fix itself.
The only workaround I have found so far is to use a pre-scaled image that is larger that the box element with transparent background, rather than scaling the image with CSS.</pre>
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