97484 2012-09-24 14:44:15 -0700 [Sub-pixel layout] incorrect rendering when painting sub-layers as their own root 2012-10-05 19:01:49 -0700 1 1 1 Unclassified WebKit Layout and Rendering 528+ (Nightly build) Unspecified Unspecified RESOLVED FIXED P2 Normal --- 1 leviw leviw eae eric jamesr simon.fraser oldest_to_newest 727018 0 leviw 2012-09-24 14:44:15 -0700 Upstream bug: http://code.google.com/p/chromium/issues/detail?id=150624 RenderLayerBacking::paintIntoLayer passes LayoutSize() into RenderLayer::paint, which can result in off-by-one paint errors with sub-pixel layout enabled. It should use the sub-pixel fraction from the root layer. I'm not sure of how, or if, this can be tested with a LayoutTest... 728910 1 leviw 2012-09-26 13:18:39 -0700 My previous comment wasn't entirely accurate. The issue comes to losing the correct sub-pixel offset by virtue of the layer bounds being zero when painting a layer in a vacuum. This is because convertToLayerCoords is a no-op when we're treating ourselves as our own root. 728914 2 165860 leviw 2012-09-26 13:23:58 -0700 Created attachment 165860 Fixes the one known occurrence of the bug This eliminates the issue that I've seen, but I'm not convinced this is the right thing for all cases. I'm continuing to investigate... 731026 3 166324 leviw 2012-09-28 15:30:56 -0700 Created attachment 166324 Patch 731848 4 166324 eric 2012-10-01 11:47:10 -0700 Comment on attachment 166324 Patch View in context: https://bugs.webkit.org/attachment.cgi?id=166324&action=review Seems reasonable. I normally defer to Simon or James for Layer reviews, so you might want to poke one of them in #webkit to make sure. > Source/WebCore/ChangeLog:9 > + happens, a sub-RenderLayer is called to paint as its own root. Normally, we attempt to preserve a non-root render layer? 734038 5 leviw 2012-10-03 14:29:44 -0700 Committed r130322: <http://trac.webkit.org/changeset/130322> 736163 6 166324 leviw 2012-10-05 19:01:49 -0700 Comment on attachment 166324 Patch Clearing flags. 165860 2012-09-26 13:23:58 -0700 2012-09-28 15:30:52 -0700 Fixes the one known occurrence of the bug patch text/plain 1124 leviw SW5kZXg6IFNvdXJjZS9XZWJDb3JlL3JlbmRlcmluZy9SZW5kZXJMYXllci5jcHAKPT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09 PQotLS0gU291cmNlL1dlYkNvcmUvcmVuZGVyaW5nL1JlbmRlckxheWVyLmNwcAkocmV2aXNpb24g MTI5MDE3KQorKysgU291cmNlL1dlYkNvcmUvcmVuZGVyaW5nL1JlbmRlckxheWVyLmNwcAkod29y a2luZyBjb3B5KQpAQCAtMTQ1OCw4ICsxNDU4LDcgQEAKIAogdm9pZCBSZW5kZXJMYXllcjo6Y29u dmVydFRvTGF5ZXJDb29yZHMoY29uc3QgUmVuZGVyTGF5ZXIqIGFuY2VzdG9yTGF5ZXIsIExheW91 dFBvaW50JiBsb2NhdGlvbikgY29uc3QKIHsKLSAgICBpZiAoYW5jZXN0b3JMYXllciA9PSB0aGlz 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