One mouse down fires the event twice.

When I set mouse event for some element that is not a Button(like Label), callback will be called twice.

The following is what I tried.
I placed a Button and a Label, and clicked each once.
Please see that the callback is called twice for the label.

Code (UXML):

1.  
2. <?xml version="1.0" encoding="utf-8"?>
3. <engine:UXML
4.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
5.     xmlns:engine="UnityEngine.UIElements"
6.     xmlns:editor="UnityEditor.UIElements"
7.     xsi:noNamespaceSchemaLocation="../UIElementsSchema/UIElements.xsd"
8. >
9.  
10.     <engine:Button text="button"/>
11.     <engine:Label text="label" style="background-color:tomato;"/>
12.  
13. </engine:UXML>
14.  

Code (CSharp):

1.  
2. public class ClickTest : MonoBehaviour
3. {
4.     private void Awake()
5.     {
6.         var root = GetComponent<UIDocument>().rootVisualElement;
7.  
8.         var button = root.Q<Button>();
9.         button.clicked += () => Debug.Log("Button clicked");
10.  
11.         var label = root.Q<Label>();
12.         label.RegisterCallback<PointerDownEvent>(e => Debug.Log("Label clicked"));
13.     }
14. }
15.  

Other test is below.
1. The test uses PointerDownEvent, but the same is true for MouseDownEvent.
2. PointerMoveEvent also appears to have a callback called twice.
3. The callbacks for PointerEnterEvnet, PointerOutEvent were called correctly.

 

Sorry. I overlooked the relevant part of the manual.

https://docs.unity3d.com/2021.2/Documentation/Manual/UIE-Events-Handling.html

Manual says
Each element along the propagation path (except the target) can receive an event twice:

• Once during the trickle-down phase.
• Once during the bubble-up phase.

Now, I still want to know how to detect that current event is in trickle-down or bubble-up.

 

These should help you with what you want.

bool -> EventBase.bubbles
bool -> EventBase.tricklesDown
Enum -> EventBase.propagationPhase

Example:

Code (CSharp):

1. void UISetup(){
2.     var root = GetComponent<UIDocument>().rootVisualElement;
3.     var label = root.Q<Label>();
4.     label.RegisterCallback<PointerDownEvent>(PointerDown);
5. }
6.  
7. void PointerDown(PointerDownEvent e){
8.     if(e.propagationPhase == PropagationPhase.AtTarget){
9.         Debug.Log("Label clicked")}
10.     }
11. }

Here is the full reference/info for EventBase:
https://docs.unity3d.com/2021.2/Documentation/ScriptReference/UIElements.EventBase.html

 

@RyanJEC
Thank you very much!
What you told me is exactly what I want to know.

 

@RyanJEC

I am sorry for the delay, but I have tested the code you gave me.
As a result, "Label Clicked" was displayed twice again.
I run the following code to check the content of the data.

Code (CSharp):

1.  
2. void PointerDown(PointerDownEvent e){
3.                 Debug.Log("-------------");
4.                 Debug.Log(e.bubbles);
5.                 Debug.Log(e.tricklesDown);
6.                 Log(e.propagationPhase);
7. }
8.  

And I got the result as below.

-------------
True
True
AtTarget
-------------
True
True
AtTarget

it seems to contain the same data both times.
Is there anything you can tell me about the cause?

 

@mcoted3d
Thank you for your reply.

I'm using uitoolkit included in Unity 2021.2.0b15.
And my OS is Ubuntu 20.04.

Here is manifest.json
---------------------
...
"com.unity.modules.ui": "1.0.0",
"com.unity.modules.uielements": "1.0.0",
...
---------------------

I have created a repository that can reproduce this behavior.
This is the very small unity project that I used when I took the first screenshot I posted.
https://github.com/mutsuyuki/UIToolkitClickTest.git

 

@mcoted3d

As you expected, I run same project on Windows and did not have this problem.
I usually using Unity on Linux. So I am looking forward to this behavior will fix.

 

@mcoted3d
Thank you for your advice.

I sent bug report.
This is issue URL.
https://fogbugz.unity3d.com/default.asp?1374865_21163kk8bkhnok01