[webkit-changes] [WebKit/WebKit] 3df543: [iOS] [SelectionHonorsOverflowScrolling] Overflow ...

[Wenson Hsieh]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 3df5437fcea8f1902bf5728215ee7309d4a4db6d
      https://github.com/WebKit/WebKit/commit/3df5437fcea8f1902bf5728215ee7309d4a4db6d
  Author: Wenson Hsieh <wenson_hsieh at apple.com>
  Date:   2024-12-03 (Tue, 03 Dec 2024)

  Changed paths:
    A LayoutTests/editing/selection/ios/scroll-overflow-container-with-selection-expected.txt
    A LayoutTests/editing/selection/ios/scroll-overflow-container-with-selection.html
    M Source/WebKit/UIProcess/ios/WKContentViewInteraction.h
    M Source/WebKit/UIProcess/ios/WKContentViewInteraction.mm
    M Source/WebKit/UIProcess/ios/WKScrollView.mm
    M Source/WebKit/UIProcess/ios/WKTextInteractionWrapper.h
    M Source/WebKit/UIProcess/ios/WKTextInteractionWrapper.mm

  Log Message:
  -----------
  [iOS] [SelectionHonorsOverflowScrolling] Overflow containers are unscrollable when text outside of the container is selected
https://bugs.webkit.org/show_bug.cgi?id=283804
rdar://140308383

Reviewed by Richard Robinson.

On iOS, when `SelectionHonorsOverflowScrolling` is enabled, the text selection display interaction
can be installed under arbitrary compositing views in the UI-side layer tree/compositing view
hierarchy. However, this exposes a bug in which the text selection display interaction's managed
selection views (i.e. native container views that encapsulate the selection highlight view, range
adjustment handles, and other UI affordances managed by the interaction) will block hit-testing
underneath the `WKScrollView`, if the compositing view that contains the selection contains child
scroll views. This prevents UIKit from routing `UITouchEvent`s to the proper child scroll view under
the gesture location (and therefore prevents scrolling), if the text selection display interaction
is installed on anything that covers the child scroller.

>From manual testing, it seems generally safe to mark these selection display interaction containers
with `userInteractionEnabled := NO`, since their child views (e.g. range adjustment handles) have
user interaction enabled, and the only other gesture relevant to this interaction is tapping to
toggle edit menu visibility, which isn't affected by whether or not these container views are
interactive due to the fact that the text tap gesture is installed over the content view. To limit
unnecessary bincompat risk (and because this probably uniquely affects WebKit's integration of the
selection display interaction), we mitigate this by overriding `-[WKScrollView hitTest:withEvent:]`
and forcing `userInteractionEnabled` to be `NO` for these managed container views over the scope of
hit-testing.

* LayoutTests/editing/selection/ios/scroll-overflow-container-with-selection-expected.txt: Added.
* LayoutTests/editing/selection/ios/scroll-overflow-container-with-selection.html: Added.

Add a layout test to exercise the bug, by selecting text in the mainframe and then attempting to
scroll an overflow container below it via pan gesture.

* Source/WebKit/UIProcess/ios/WKContentViewInteraction.h:
* Source/WebKit/UIProcess/ios/WKContentViewInteraction.mm:
(-[WKContentView makeTextSelectionViewsNonInteractiveForScope]):

Add a helper method that returns a RAII object (`ScopeExit`), which callers can use to temporarily
make selection container views non-interactive. See above for more details.

* Source/WebKit/UIProcess/ios/WKScrollView.mm:
(-[WKScrollView hitTest:withEvent:]):

Call `-makeTextSelectionViewsNonInteractiveForScope` when hit-testing.

* Source/WebKit/UIProcess/ios/WKTextInteractionWrapper.h:
* Source/WebKit/UIProcess/ios/WKTextInteractionWrapper.mm:
(-[WKTextInteractionWrapper managedTextSelectionViews]):
(-[WKTextInteractionWrapper prepareToMoveSelectionContainer:]):

Add logic to keep track of all the managed views of the text selection display interaction, by
observing which views were introduced to the target container view as a result of invoking
`-didMoveToView:`.

Canonical link: https://commits.webkit.org/287294@main



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