Bug 109236 – Refine requirements for opting into composited scrolling

• Status: NEW
• Component: WebCore Misc.

Previously, we had required that a layer's z-ordered descendants form a contiguous block in stacking order (and that that block appeared just before or after the normal flow list). This turned out to be inaccurate. If the layer has a positioned ancestor with z-index 0, then the layer will paint after it's positioned ancestor rather than with the other normal flow elements. Really, we need to ensure that all of the following are in a contiguous block:

1. The z-ordered descendants.
2. The old position of the layer in the stack order (taking into account positioned ancestors).
3. The new (if promoted) position of the layer in stack order.

Created attachment 187210 [details]
Patch

[Build Bot]

Comment on attachment 187210 [details]
Patch

Attachment 187210 [details] did not pass mac-wk2-ews (mac-wk2):
Output: http://queues.webkit.org/results/16430394

[Build Bot]

Comment on attachment 187210 [details]
Patch

Attachment 187210 [details] did not pass mac-ews (mac):
Output: http://queues.webkit.org/results/16435422

Created attachment 187218 [details]
Attempt to fix mac builds.

Created attachment 190552 [details]
Patch

[Early Warning System Bot]

Comment on attachment 190552 [details]
Patch

Attachment 190552 [details] did not pass qt-wk2-ews (qt):
Output: http://webkit-commit-queue.appspot.com/results/16791110

[WebKit Review Bot]

Comment on attachment 190552 [details]
Patch

Attachment 190552 [details] did not pass chromium-ews (chromium-xvfb):
Output: http://webkit-commit-queue.appspot.com/results/16675190

New failing tests:
platform/chromium/virtual/gpu/compositedscrolling/scrollbars/scrollbar-initial-position.html
platform/chromium/virtual/softwarecompositing/overflow/textarea-scroll-touch.html
platform/chromium/virtual/gpu/compositedscrolling/scrollbars/scrollevent-iframe-no-scrolling.html
compositing/overflow/textarea-scroll-touch.html
platform/chromium/virtual/gpu/compositedscrolling/overflow/overflow-compositing-descendant.html
platform/chromium/virtual/gpu/compositedscrolling/scrollbars/scrollable-iframe-remove-crash.html
platform/chromium/virtual/gpu/compositedscrolling/scrollbars/scrollevent-iframe-no-scrolling-wheel.html
platform/chromium/virtual/gpu/compositedscrolling/overflow/textarea-scroll-touch.html
platform/chromium/virtual/gpu/compositedscrolling/scrollbars/overflow-scrollbar-combinations.html

[Build Bot]

Comment on attachment 190552 [details]
Patch

Attachment 190552 [details] did not pass mac-wk2-ews (mac-wk2):
Output: http://webkit-queues.appspot.com/results/100063

New failing tests:
compositing/overflow/do-not-paint-outline-into-composited-scrolling-contents.html

[Build Bot]

Created attachment 197733 [details]
Archive of layout-test-results from webkit-ews-12 for mac-mountainlion-wk2

The attached test failures were seen while running run-webkit-tests on the mac-wk2-ews.
Bot: webkit-ews-12  Port: mac-mountainlion-wk2  Platform: Mac OS X 10.8.2

[Darin Adler]

Comment on attachment 190552 [details]
Patch

review- on this really old patch; might still be an improvement, but not sure it’s relevant to WebKit not