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Correctly implement the UIGestureRecognizer state machine #2004

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Correctly implement the UIGestureRecognizer state machine #2004

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a1da321
Correctly implement the UIGestureRecognizer state machine
filipnavara Jul 7, 2024
4f9331b
Merge branch 'main' into apple-touch-state-machine
brminnick Jul 24, 2024
9c596db
Merge branch 'main' into apple-touch-state-machine
brminnick Dec 18, 2024
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21 changes: 11 additions & 10 deletions src/CommunityToolkit.Maui/Behaviors/PlatformBehaviors/Touch/TouchBehavior.macios.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -203,6 +203,16 @@ void HandleTouch(TouchStatus status, TouchInteractionStatus? interactionStatus =
return;
}

// We MUST implement the Apple state machine. This ensures that the interaction
// between multiple simultaneous touch recognizers works correctly.
// https://developer.apple.com/documentation/uikit/touches_presses_and_gestures/implementing_a_custom_gesture_recognizer/about_the_gesture_recognizer_state_machine?language=objc
State = status switch
{
TouchStatus.Canceled => UIGestureRecognizerState.Failed,
TouchStatus.Completed => UIGestureRecognizerState.Recognized,
_ => UIGestureRecognizerState.Possible,
};

if (interactionStatus is TouchInteractionStatus.Started)
{
behavior.HandleUserInteraction(TouchInteractionStatus.Started);
Expand Down Expand Up @@ -231,19 +241,10 @@ public override bool ShouldRecognizeSimultaneously(UIGestureRecognizer gestureRe
{
touchGesture.HandleTouch(TouchStatus.Canceled, TouchInteractionStatus.Completed);
touchGesture.isCanceled = true;
}

return true;
}

public override bool ShouldReceiveTouch(UIGestureRecognizer recognizer, UITouch touch)
{
if (recognizer.View.IsDescendantOfView(touch.View))
{
return true;
}

return touch.View.IsDescendantOfView(recognizer.View) && (touch.View.GestureRecognizers is null || touch.View.GestureRecognizers.Length == 0);
return false;
}
}
}
Expand Down