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Question Prevent pointer clicks through elements

Discussion in 'UI Toolkit' started by StripeGuy, Aug 22, 2023.

  1. StripeGuy

    StripeGuy

    Joined:
    Dec 30, 2016
    Posts:
    52
    I am making a drawing application using UI toolkit, but when I have an element "popup" over an the draw area, both the popup and the draw area get pointer clicks.

    I am using a callback for the drawarea, and tried both "Trickledown" and "NoTrickledown", but nothing blocks the clicks.

    ex callback for draw area:
    Code (CSharp):
    1. drawareaVisualElement.RegisterCallback<PointerDownEvent>(OnPointerDown, TrickleDown.NoTrickleDown);
    The popup element panels don't really have a callback (only the controls do - radiobuttons, etc.), so not sure how I would handle "trickledown" for the whole panel.
     
    StripeGuy, Aug 22, 2023
    #1

  2. karl_jones

    karl_jones

    Unity Technologies

    Joined:
    May 5, 2015
    Posts:
    7,820
    Have you tried calling StopPropagation on the event inside of OnPointerDown?
     
    karl_jones, Aug 22, 2023
    #2

  3. StripeGuy

    StripeGuy

    Joined:
    Dec 30, 2016
    Posts:
    52
    Hey, thanks for the quick reply :)

    So looking online I would use it as "evt.StopPropagation();". But when I put it under "OnPointerDown" or even "OnPointerEnter" of the draw area, clicks on my popup panel still "draw" under it.

    Would I need to add the StopPropagation() on my popup panel somehow instead?

    Edit: So I created an OnPointerDown callback for my popup panel, and in there I added the StopPropogation(). This seems to work now. But does that mean I have to create a callback for every single popup I create in my UI to stop the propogation? Or is there a universal way of defaulting to StopPropogation?
     
    Last edited: Aug 22, 2023
    StripeGuy, Aug 22, 2023
    #3

  4. karl_jones

    karl_jones

    Unity Technologies

    Joined:
    May 5, 2015
    Posts:
    7,820
    Yes you will need to do it for every popup element.

    You may want to create a specific VisualElement type that does this

    Code (csharp):
    1. class BlockerElement : VisualElement {
    2.  #if UNITY_2023_2_OR_NEWER
    3.      protected override void HandleEventBubbleUp(EventBase evt) => OnHandleEvent(evt);
    4.  #else
    5.      protected override void ExecuteDefaultAction(EventBase evt) => OnHandleEvent(evt);
    6.  #endif
    7.  
    8.      void OnHandleEvent(EventBase evt)
    9.      {
    10.          if (evt is AttachToPanelEvent)
    11.               RegisterCallback<PointerDownEvent>(StopPointerPropagation, TrickleDown.TrickleDown);
    12.          else if (evt is DetachFromPanelEvent)
    13.               UnregisterCallback<PointerDownEvent>(StopPointerPropagation, TrickleDown.TrickleDown);
    14.      }
    15.      void StopPointerPropagation(PointerDownEvent evt) => evt.StopPropagation();
    16.  }
    This page has good information on how events propagate
    https://docs.unity3d.com/Manual/UIE-Events-Dispatching.html

    Depending how the hierarchy's built you may need to keep the "drawing" logic during the BubbleUp phase so the popups/overlays have a chance to stop event propagation before the canvas has a chance to handle the event itself
     
    karl_jones, Aug 22, 2023
    #4

  5. StripeGuy

    StripeGuy

    Joined:
    Dec 30, 2016
    Posts:
    52
    That's awesome! :) Thank you so much for answering my question. Need more people like you on the Unity team.
     
    StripeGuy, Aug 22, 2023
    #5
    karl_jones likes this.

  6. karl_jones

    karl_jones

    Unity Technologies

    Joined:
    May 5, 2015
    Posts:
    7,820
    I can't take full credit for that one, another team member gave me the answer :D
     
    karl_jones, Aug 22, 2023
    #6
    StripeGuy likes this.