Question by AlexDavies · Jul 01, 2020 at 02:43 PM · editorgui editor window uitoolkit

UIElements display:none not working properly

I'm getting some really strange behavior when setting the display-style of a button. The expected behavior is that the install button acts as if it doesn't exist (can be seen at end of gif) - it is invisible and removed from the layout. Setting the style inline or through a style sheet has the expected behavior, but is not dynamic (and is therefore not very useful). My code: C#:

 var installButton = rootVisualElement.Q<Button>("plugin-install-button");
 var removeButton = rootVisualElement.Q<Button>("plugin-remove-button");
 var updateButton = rootVisualElement.Q<Button>("plugin-update-button");
 
 installButton.style.display = pluginInstalled ? DisplayStyle.None : DisplayStyle.Flex;
 removeButton.style.display = pluginInstalled ? DisplayStyle.Flex : DisplayStyle.None;
 updateButton.style.display = pluginInstalled ? DisplayStyle.Flex : DisplayStyle.None;

UXML:

 <engine:Button name="plugin-install-button" text="Install"/>
 <engine:Button name="plugin-update-button" text="Update"/>
 <engine:Button name="plugin-remove-button" text="Remove"/>

First, the button remains visible until I resize the window. The layout is still incorrect even after it dissappears. Calling MarkDirtyRepaint() on either the buttons, their parents, or the root does nothing, and calling EditorWindow.Repaint() also does nothing. The only way that I can get the layout to update correctly is by changing the display property in the UIElements Debugger to 'flex' and then back to 'none'. example gif Note: I'm using Unity 2020.1.0b4

EDIT: I think that my problem may be caused by calling the C# code below from asynchronous code. (I think from another thread). This might be incorrect though, as using VisualElement.schedule to effectively queue actions didn't solve the problem.

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exploringunity · Jul 13, 2020 at 04:53 PM 0

Hey @$$anonymous$$Davies, I don't think there's enough context to solve this issue -- could you share some more code? Is that C# code in your EditorWindow class's OnEnable? You mentioned async/threading?

AlexDavies · Jul 13, 2020 at 05:30 PM 0

The code is called in a callback method from System.Diagnostics.Process.Start(), or more specifically, in the callback for Process.Exited (which is run when the process has completed its task). In this case the process call is to run some git commands.

The original call to Process.Start is in the EditorWindow’s OnEnable.

andrew-lukasik · Jul 13, 2020 at 08:50 PM 0

Try running this async code in try/catch block, where catch uses Debug.LogException. You may see hidden exception here.

AlexDavies · Jul 13, 2020 at 10:19 PM 0

Fortunately (or unfortunately for the future), I no longer have the code for it as I refactored it to not need to change the buttons this way. I think it's unlikely to be an exception, given that it correctly runs the code - the display property does change, it just doesn't seem to trigger a repaint or layout update. It's almost as if it's not detecting the change.

andrew-lukasik AlexDavies · Jul 13, 2020 at 10:30 PM 0

Unity throws exceptions when foreign thread calls !thread-safe functions,`Repaint` for example

exploringunity andrew-lukasik · Jul 13, 2020 at 11:20 PM 1

+1 to what @andrew-lukasik said. Here's a minimal demo -- if you create a basic UIElements editor window and add a simple async call like this...

     public void OnEnable {
 ... // default stuff from Create -> UIElements -> Editor Window
         root.Add(labelWithStyle);
         Task.Run(() => HideLabel(labelWithStyle));
     }
 
     public void HideLabel(Label lbl)
     {
         try
         {
             Debug.Log("Starting sleep.");
             System.Threading.Thread.Sleep(2000);
             Debug.Log("Sleep complete.");
             lbl.style.display = DisplayStyle.None;
         }
         catch (System.Exception e)
         {
             Debug.Log($"{e}");
         }
     }

... you'll get an Exception like so:

An exception was logged that says

If you tried to modify the layout, for example using rootVisualElement.Clear(), you'd get a similar exception -- UnityEngine.UnityException: YGNodeRemoveChild can only be called from the main thread.

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