REGRESSION (262853@main): [iOS] 2 fast/scrolling/ios/click-events-dur…

…ing-momentum-scroll-* tests consistently failing

https://bugs.webkit.org/show_bug.cgi?id=255415
rdar://108011669

Reviewed by Tim Horton.

A couple of iOS layout tests began failing consistently after 262853@main; these two tests:

1. Scroll in a web page (either in the mainframe or an overflow scroller).
2. Tap the page while the scroll is decelerating.
3. Verify that the tap in step (2) did not trigger any click events.

While I'm only able to rarely reproduce this on device, it appears to readily reproduce when using
the simulator; I suspect this is because the touch point doesn't change at all when using the
trackpad or synthesizing taps in the simulator/testing environment, which causes the scroll view pan
gesture to never receive any touch moves.

We can fix this by only allowing simultaneous gesture recognition between the single tap and pan
gesture, in the case where the touch isn't interrupting scroll view deceleration.

* Source/WebKit/UIProcess/ios/WKContentViewInteraction.mm:
(-[WKContentView gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer:]):
(-[WKContentView _isInterruptingDecelerationForScrollViewOrAncestor:]):

Move this logic out of a local C++ lambda function inside of `-gestureRecognizerShouldBegin:`, and
into a separate helper method so that we can use it above as well, in
`-gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer:`.

(-[WKContentView gestureRecognizerShouldBegin:]):

Canonical link: https://commits.webkit.org/262963@main

Source/WebKit/UIProcess/ios/WKContentViewInteraction.mm

@@ -2566,7 +2566,8 @@ - (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecogni
         return ![self shouldDeferGestureDueToImageAnalysis:gestureRecognizer];
 #endif
 
-    if (gestureRecognizer == _singleTapGestureRecognizer && [otherGestureRecognizer isKindOfClass:UIPanGestureRecognizer.class])
+    if (gestureRecognizer == _singleTapGestureRecognizer && [otherGestureRecognizer isKindOfClass:UIPanGestureRecognizer.class]
+        && ![self _isInterruptingDecelerationForScrollViewOrAncestor:[_singleTapGestureRecognizer lastTouchedScrollView]])
         return YES;
 
     if (isSamePair(gestureRecognizer, otherGestureRecognizer, _highlightLongPressGestureRecognizer.get(), _longPressGestureRecognizer.get()))
@@ -2868,29 +2869,30 @@ - (BOOL)_shouldToggleSelectionCommandsAfterTapAt:(CGPoint)point
     return pointIsInSelectionRect;
 }
 
-- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
+- (BOOL)_isInterruptingDecelerationForScrollViewOrAncestor:(UIScrollView *)scrollView
 {
-    CGPoint point = [gestureRecognizer locationInView:self];
+    UIScrollView *mainScroller = self.webView.scrollView;
+    UIView *view = scrollView ?: mainScroller;
+    while (view) {
+        if (dynamic_objc_cast<UIScrollView>(view)._isInterruptingDeceleration)
+            return YES;
 
-    auto isInterruptingDecelerationForScrollViewOrAncestor = [&] (UIScrollView *scrollView) {
-        UIScrollView *mainScroller = self.webView.scrollView;
-        UIView *view = scrollView ?: mainScroller;
-        while (view) {
-            if ([view isKindOfClass:UIScrollView.class] && [(UIScrollView *)view _isInterruptingDeceleration])
-                return YES;
+        if (mainScroller == view)
+            break;
 
-            if (mainScroller == view)
-                break;
+        view = view.superview;
+    }
+    return NO;
+}
 
-            view = view.superview;
-        }
-        return NO;
-    };
+- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
+{
+    CGPoint point = [gestureRecognizer locationInView:self];
 
     if (gestureRecognizer == _singleTapGestureRecognizer) {
         if ([self _shouldToggleSelectionCommandsAfterTapAt:point])
             return NO;
-        return !isInterruptingDecelerationForScrollViewOrAncestor([_singleTapGestureRecognizer lastTouchedScrollView]);
+        return ![self _isInterruptingDecelerationForScrollViewOrAncestor:[_singleTapGestureRecognizer lastTouchedScrollView]];
     }
 
     if (gestureRecognizer == _doubleTapGestureRecognizerForDoubleClick) {
@@ -2919,7 +2921,7 @@ - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
     }
 
     if (gestureRecognizer == _highlightLongPressGestureRecognizer) {
-        if (isInterruptingDecelerationForScrollViewOrAncestor([_highlightLongPressGestureRecognizer lastTouchedScrollView]))
+        if ([self _isInterruptingDecelerationForScrollViewOrAncestor:[_highlightLongPressGestureRecognizer lastTouchedScrollView]])
             return NO;
 
         if (self._hasFocusedElement) {