[webkit-changes] [WebKit/WebKit] b289d5: REGRESSION (UI-side compositing?): Sporadic failur...

[Simon Fraser]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: b289d5f2461d7da84861df406cee682afa4c39df
      https://github.com/WebKit/WebKit/commit/b289d5f2461d7da84861df406cee682afa4c39df
  Author: Simon Fraser <simon.fraser at apple.com>
  Date:   2024-03-21 (Thu, 21 Mar 2024)

  Changed paths:
    M Source/WebKit/UIProcess/API/Cocoa/WKWebView.mm
    M Source/WebKit/UIProcess/Cocoa/WebPageProxyCocoa.mm
    M Source/WebKit/UIProcess/WebPageProxy.cpp
    M Source/WebKit/UIProcess/WebPageProxy.h

  Log Message:
  -----------
  REGRESSION (UI-side compositing?): Sporadic failures in layout tests due to wrong test images
https://bugs.webkit.org/show_bug.cgi?id=271348
rdar://120050275

Reviewed by Tim Horton.

When we take snapshots of layout tests, we wait for a `callAfterNextPresentationUpdate()`, which
waits for a transaction to come from the web process. However, it doesn't wait for the subsequent
Core Animation commit, which actually pushes changes to WindowServer. Yet the snapshot we do is
a WindowServer snapshot (`PlatformWebView::windowSnapshotImage()`), so we can sometimes capture state that is stale.

We don't actually know when our new content gets to WindowServer and will show up in a snapshot,
but we can reduce the raciness by at least waiting for the Core Animation commit to complete.
So add `callAfterNextPresentationUpdateAndLayerCommit()` and use it `WebPageProxy::forceRepaint()`.
Also update `-[WKWebView takeSnapshotWithConfiguration:]` to use it.

* Source/WebKit/UIProcess/API/Cocoa/WKWebView.mm:
(-[WKWebView takeSnapshotWithConfiguration:completionHandler:]):
* Source/WebKit/UIProcess/Cocoa/WebPageProxyCocoa.mm:
(WebKit::WebPageProxy::callAfterNextPresentationUpdateAndLayerCommit):
* Source/WebKit/UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::forceRepaint):
(WebKit::WebPageProxy::callAfterNextPresentationUpdateAndLayerCommit):
* Source/WebKit/UIProcess/WebPageProxy.h:

Canonical link: https://commits.webkit.org/276494@main



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