unoplatform/uno · error · InvalidOperationException

GLCanvasElement.IsGLInitializedProperty is read-only.

Error message

GLCanvasElement.IsGLInitializedProperty is read-only.

What it means

IsGLInitializedProperty is a read-only dependency property: the framework changes it only via the internal set_IsGLInitialized setter, which sets _changingGlInitialized=true around the SetValue. The property-changed callback throws InvalidOperationException if SetValue is reached while _changingGlInitialized is false — i.e. external code called SetValue(IsGLInitializedProperty, ...) directly, or a nested re-entrant SetValue from a property-changed handler. The throw is intentional to forbid external mutation and re-entrancy.

Source

Thrown at src/AddIns/Uno.WinUI.Graphics3DGL/GLCanvasElement.cs:285

		internal override SkiaSharp.SKPath? Paint(in PaintingSession session)
		{
			NativeDispatcher.Main.Enqueue(owner.Render, NativeDispatcherPriority.High);
			return base.Paint(session);
		}
	}
#endif

	public static DependencyProperty IsGLInitializedProperty { get; } =
		DependencyProperty.Register(
			nameof(IsGLInitialized),
			typeof(bool?),
			typeof(GLCanvasElement),
			new PropertyMetadata(null, (PropertyChangedCallback)((dO, _) =>
			{
				var @this = (GLCanvasElement)dO;
				if (!@this._changingGlInitialized)
				{
					throw new InvalidOperationException($"{nameof(GLCanvasElement)}.{nameof(IsGLInitializedProperty)} is read-only.");
				}

				// We should have arrived here from set_IsGLInitialized, so we could put this line at the end of the
				// setter. Instead, we set it to false here to prevent users from calling SetValue.IsGLInitializedProperty
				// _inside_ a call to GLCanvasElement.set_IsGLInitialized. This way, if a user intercepts this
				// change (e.g. with SubscribeToPropertyChanged) and attempts to make a nested SetValue call, we still
				// explode in their face.
				@this._changingGlInitialized = false;
			})));

	/// <summary>
	/// Indicates whether this element was loaded successfully or not, including the OpenGL context creation and setup.
	/// This property is only valid when the element is loaded. When the element is not loaded in the visual tree, the value will be null.
	/// The value also becomes false if an exception escapes <see cref="Init"/>, <see cref="RenderOverride"/> or the
	/// framebuffer setup, in which case the element stops rendering until it is reloaded.
	/// </summary>
	public bool? IsGLInitialized
	{

View on GitHub (pinned to 0418340488)

Solutions

1. Treat IsGLInitialized as read-only: never call SetValue on it from app code; read it via the IsGLInitialized getter only.
2. If you must react to it, subscribe via the property-changed callback for observation only and do NOT re-SetValue the same property.
3. Remove any two-way binding or local XAML value set on IsGLInitializedProperty.

Example fix

// before
element.SetValue(GLCanvasElement.IsGLInitializedProperty, true);

// after
// IsGLInitialized is set by the framework after GL context creation.
// Read-only: observe it instead of writing it.
bool ready = element.IsGLInitialized ?? false;

// IsGLInitialized is read-only; never call SetValue on it from app code.
bool ready = element.IsGLInitialized ?? false;

When it happens

Trigger: User code calls element.SetValue(GLCanvasElement.IsGLInitializedProperty, value); or a RegisterDisposablePropertyChangedCallback/OnPropertyChanged handler for IsGLInitialized calls SetValue on the same property, racing past the _changingGlInitialized reset.

Common situations: Binding IsGLInitialized two-way from a view-model; calling element.SetValue in a property-changed handler; XAML with a local value set on the read-only property.

Related errors

• Offscreen framebuffer is not complete
• The framebuffer readback failed with {readbackError} while c
• MediaPlayerPresenterExtension must be initialized with a Med
• Owner must be a SvgImageSource instance.
• ChoosePixelFormat failed

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/3daa933b691bdefa. Report an issue: GitHub.