[iOS WK2] When zoomed in and panning on pages with fixed bars, parts of the bars are sometimes missing

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Simon Fraser (smfr)]

On a page like http://smfr.org/misc/four-bars-shadows.html, if you zoom in and pan around, bits of the bars are sometimes missing.

This happens when they get into tiled mode, but we fail to update the tiles during scrolling.

This is related to https://trac.webkit.org/changeset/186155.

[Simon Fraser (smfr)]

Created attachment 295023 [details]
Patch

[Radar WebKit Bug Importer]

<rdar://problem/29303891>

[Radar WebKit Bug Importer]

<rdar://problem/29303889>

[Simon Fraser (smfr)]

Created attachment 295024 [details]
Patch

[Simon Fraser (smfr)]

Created attachment 295030 [details]
Patch

[Build Bot]

Comment on attachment 295030 [details]
Patch

Attachment 295030 [details] did not pass ios-sim-ews (ios-simulator-wk2):
Output: http://webkit-queues.webkit.org/results/2529833

New failing tests:
scrollingcoordinator/ios/sync-layer-positions-after-scroll.html

[Build Bot]

Created attachment 295036 [details]
Archive of layout-test-results from ews125 for ios-simulator-wk2

The attached test failures were seen while running run-webkit-tests on the ios-sim-ews.
Bot: ews125  Port: ios-simulator-wk2  Platform: Mac OS X 10.11.6

[Sam Weinig]

Comment on attachment 295030 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=295030&action=review

> Source/WebCore/platform/graphics/GraphicsLayer.h:605
> +    // If set, overrides m_position. Only used for coverage computation.
> +    Optional<FloatPoint> m_approximatePosition;

This could use a slightly more in depth comment, as the term approximate is a bit scary.

[Simon Fraser (smfr)]

Some test infrastructure in bug 164905.

[Simon Fraser (smfr)]

https://trac.webkit.org/changeset/208927