Add a new property shouldCenterActivationPoint to NIViewAccessibilityElement.

This property ensures multiline NIViewAccessibilityElements have unique touch points when merging multiline links into a single NIViewAccessibilityElement. When the first link contains either the first or the last word in the sentence and the second link spills between more than one line, the NIViewAccessibilityElement frames have the same top left point, which is used as the touch point. This causes an issue where NIAttributedLabel can't determine which accessibilityElement a touchPoint originated from, meaning that one of the  two links can't register events. We solve this by using the center point of the frame, which is ensured to be unique (only for links in the same text) as multiline element frames would have unique y-coordinates.

PiperOrigin-RevId: 544181302

Author: Nobody

src/attributedlabel/src/NIAttributedLabel.m

@@ -173,6 +173,17 @@ @interface NIViewAccessibilityElement ()
 // performed.
 @property (nonatomic) BOOL isContainerDataValid;
 
+// This property ensures multiline NIViewAccessibilityElements have unique
+// touch points when merging multiline links into a single NIViewAccessibilityElement.
+// When the first link contains either the first or the last word in the sentence and the second
+// link spills between more than one line, the NIViewAccessibilityElement
+// frames have the same top left point, which is used as the touch point. This causes an
+// issue where NIAttributedLabel can't determine which accessibilityElement a touchPoint
+// originated from, meaning that one of the  two links can't register events.
+// We solve this by using the center point of the frame, which is ensured to be unique
+// (only for links in the same text) as multiline element frames would have unique y-coordinates.
+@property (nonatomic) BOOL shouldCenterActivationPoint;
+
 @end
 
 @implementation NIViewAccessibilityElement
@@ -204,6 +215,7 @@ - (instancetype)initWithAccessibilityContainer:(id)container {
                                  frameInContainer:CGRectZero
                                 pointsInContainer:nil]) {
     self.isContainerDataValid = NO;
+    self.shouldCenterActivationPoint = NO;
   }
   return self;
 }
@@ -273,6 +285,13 @@ - (CGPoint)accessibilityActivationPoint {
     point = [accessibilityContainerView.window convertPoint:point toWindow:nil];
     return point;
   }
+  if (_shouldCenterActivationPoint) {
+    // Since links cannot overlap, using the center of the start and end points
+    // of the explicit link location ensures unique touch points from events.
+    CGPoint startPoint = [[_pointsInContainer firstObject] CGPointValue];
+    CGPoint endPoint = [[_pointsInContainer lastObject] CGPointValue];
+    return CGPointMake((startPoint.x+endPoint.x)/2.0, (startPoint.y+endPoint.y)/2.0);
+  }
   return super.accessibilityActivationPoint;
 }
 
@@ -1911,6 +1930,7 @@ - (NSArray *)accessibleElements {
         NIViewAccessibilityElement *element = [[NIViewAccessibilityElement alloc]
             initWithAccessibilityContainer:self
                           frameInContainer:rectValue.CGRectValue];
+        element.shouldCenterActivationPoint = _shouldMergeMultilineLinks;
         [self updateAccessibilityLabelOnElement:element withAccessibilityLabel:label];
 
         // Set the frame to fallback on if |element|'s accessibility container is changed