[webkit-changes] [WebKit/WebKit] 914c16: Regression(ScreenOrientation API) Fullscreen exits...

[Chris Dumez]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 914c16e8faccc6f14fd3eef8bfaac5065509b98a
      https://github.com/WebKit/WebKit/commit/914c16e8faccc6f14fd3eef8bfaac5065509b98a
  Author: Chris Dumez <cdumez at apple.com>
  Date:   2023-02-01 (Wed, 01 Feb 2023)

  Changed paths:
    M LayoutTests/TestExpectations
    A LayoutTests/fast/dom/Orientation/no-orientation-change-event-when-unparenting-view-expected.txt
    A LayoutTests/fast/dom/Orientation/no-orientation-change-event-when-unparenting-view.html
    M LayoutTests/platform/ios/TestExpectations
    M Source/WebCore/platform/ScreenOrientationProvider.cpp
    M Source/WebCore/platform/ScreenOrientationProvider.h
    M Source/WebCore/platform/ios/ScreenOrientationProviderIOS.mm

  Log Message:
  -----------
  Regression(ScreenOrientation API) Fullscreen exits right away on Youtube
https://bugs.webkit.org/show_bug.cgi?id=251396
rdar://104269674

Reviewed by Wenson Hsieh.

When entering fullscreen on youtube, the view would lose its window and
then get added to a new Window. This would end up calling
`ScreenOrientationProvider::setWindow()` first with nil then with the new
window.

To determine the screen orientation, the ScreenOrientationProvider currently
needs access to the window object inside platformCurrentOrientation(). If
it didn't have a window, platformCurrentOrientation() would just return
PortraitPrimary.

When updating the window, setWindow() would call screenOrientationDidChange()
which would call platformCurrentOrientation() again to make sure the cached
orientation is still accurate and to notify the clients that the orientation
has changed otherwise. However, since platformCurrentOrientation() requires
a window, there is no point in calling screenOrientationDidChange() if the
new window is nil. It will just reset the orientation to the PortaitPrimary
value and potentially send an incorrect orientation change notification to
clients. This incorrect notification is what was causing the fullscreen
mode to exit (since fullscreen mode exists on orientation change).

To address this, I made 2 changes:
1. setWindow() now only calls screenOrientationDidChange() if the new
   window is non-nil.
2. platformCurrentOrientation() now returns a std::optional<> to make it
   clear when it wasn't able to determinate the orientation.
4. In screenOrientationDidChange(), if platformCurrentOrientation() returns
   std::nullopt, we now return early so that we don't send clients a
   potentially inaccurate orientation. Once the view gets added again to
   a window, we'll call screenOrientationDidChange() again to make sure
   we send a change notification if needed.

* Source/WebCore/platform/ScreenOrientationProvider.cpp:
(WebCore::ScreenOrientationProvider::screenOrientationDidChange):
(WebCore::ScreenOrientationProvider::currentOrientation):
(WebCore::ScreenOrientationProvider::platformCurrentOrientation):
* Source/WebCore/platform/ScreenOrientationProvider.h:
* Source/WebCore/platform/ios/ScreenOrientationProviderIOS.mm:
(WebCore::ScreenOrientationProvider::platformCurrentOrientation):
(WebCore::ScreenOrientationProvider::setWindow):

Canonical link: https://commits.webkit.org/259678@main