Questions about Template.path and schemeLocation in UXML

Hi, The title is all, is there any method for using relative path for Template.path?

The official sample (https://docs.unity3d.com/Manual/UIE-ElementRef.html) used full path like this:

But generally, reusable templates need to be packaged and easily changed its path. Also Custom Packages are located in Packages folder, not Assets.

So, questions are:
1. Can I use relative path?
2. Can I use templates in Packages folder?

Thanks.
Edit:
3. Is it impossible to set project root relative path for schemaLocations? It seems that current auto-generated uxml has self-relative path for scheme path, so if the uxml file is moved to other folder, it doesnt work.

 

Is there a plan to change this requirement?

Not being able to use templates in packages complicates work I'm trying to do right now.

 

Thanks, I've gotten it working as described. I appreciate the in-depth reply. I was lead astray by the error message as it doesn't hint that package relative paths are possible!

Invalid AssetDatabase path: /SandboxWindow_Package.uxml. Use path relative to the project folder.
UnityEngine.UIElements.VisualTreeAsset:CloneTree(VisualElement)

 

I found that absolute path does not work well when you are authoring the package, since the package is now in Assets/ when you are making it and "packages/com..." will not work. So in the end I use the absolute path derivation of uxml+uss from cs script file :

Code (CSharp):

1.     public void OnEnable()
2.     {
3.         // Each editor window contains a root VisualElement object
4.         VisualElement root = rootVisualElement;
5.  
6.         // VisualElements objects can contain other VisualElement following a tree hierarchy.
7.         VisualElement label = new Label("Hello World! From C#");
8.         root.Add(label);
9.  
10.         var csScriptPath = AssetDatabase.GUIDToAssetPath("6d690a34d45ba491991385dee51e3c4e");
11.         var csFileName = Path.GetFileNameWithoutExtension(csScriptPath);
12.         var csDirectory = Path.GetDirectoryName(csScriptPath);
13.  
14.         // Import UXML
15.         var visualTree = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>($"{csDirectory}/{csFileName}.uxml");
16.         VisualElement labelFromUXML = visualTree.CloneTree();
17.         root.Add(labelFromUXML);
18.  
19.         // A stylesheet can be added to a VisualElement.
20.         // The style will be applied to the VisualElement and all of its children.
21.         var styleSheet = AssetDatabase.LoadAssetAtPath<StyleSheet>($"{csDirectory}/{csFileName}.uss");
22.         VisualElement labelWithStyle = new Label("Hello World! With Style");
23.         labelWithStyle.styleSheets.Add(styleSheet);
24.         root.Add(labelWithStyle);
25.     }

 

Lazy helper method version..

Code (CSharp):

1.     public static class UxmlHelper
2.     {
3.         private static Dictionary<Type, VisualTreeAsset> cache = new Dictionary<Type, VisualTreeAsset>();
4.  
5.         /// <summary>
6.         /// Loads a `.uxml` at the same location named like the class name of its `.cs` script.
7.         /// </summary>
8.         public static VisualTreeAsset TreeOfClass<T>() where T : VisualElement
9.         {
10.             var type = typeof(T);
11.             if (cache.TryGetValue(type, out var found) == false)
12.             {
13.                 var foundGuid = AssetDatabase.FindAssets($"{typeof(T).Name} t:MonoScript").FirstOrDefault();
14.                 if (foundGuid == default)
15.                 {
16.                     throw new Exception($".uxml of {type.Name} not found.");
17.                 }
18.                 var scriptPath = AssetDatabase.GUIDToAssetPath(foundGuid);
19.                 var path = Path.GetDirectoryName(scriptPath);
20.                 var fileName = Path.GetFileNameWithoutExtension(scriptPath);
21.                 var tree = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>($"{path}/{fileName}.uxml");
22.                 cache.Add(type, tree);
23.                 return tree;
24.             }
25.             else
26.             {
27.                 return found;
28.             }
29.         }
30.     }

When using it

Code (CSharp):

1.     public class AudioGroupPicker : VisualElement
2.     {
3.         public class Traits : VisualElement.UxmlTraits { }
4.         public class Factory : UxmlFactory<AudioGroupPicker, Traits>
5.         {
6.         }
7.  
8.         public AudioGroupPicker()
9.         {
10.             UxmlHelper.TreeOfClass<AudioGroupPicker>().CloneTree(this);
11.             var groupField = this.Q<ObjectField>();
12.             groupField.objectType = typeof(AudioGroup);
13.         }
14.     }

 

@5argon you don't author the package under

Assets/

.
you embed it i.e. put it physically under

Packages/..../

and the paths are the same.
it is fully editable as if it were under

Assets/

, and if it's not you report a bug for it.
plus is treated as a package for validation purposes (e.g. no scripts without asmdefs allowed)

you can avoid the AssetDatabase call (in an editor window) by having a serialized field and assigning the asset as a default reference in the script inspector.

 

I know that this is kind of old but still applies to 2021.2.19f1 and up

To get rid of the maintenance of the relative path in xsi:noNamespaceSchemaLocation you can use

xsi:noNamespaceSchemaLocation="/../UIElementsSchema/UIElements.xsd"

At least in Jetbrains Rider, this will work. YMMV.

I'd suggest that the various wizards/code generators in unity, that will generate uxml files from templates, should make this a default.