Introduce PresentationSource, move some responsibilities from TopLevel by kekekeks · Pull Request #20624 · AvaloniaUI/Avalonia

kekekeks · 2026-02-06T10:42:31Z

See #20622

This PR mostly moves stuff around, no observable behavioral changes yet, TopLevel is currently still always the root of the tree.

Based on another PR, so the diff is bigg

# Conflicts: # tests/Avalonia.Controls.UnitTests/TabControlTests.cs

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Pull request overview

Copilot reviewed 104 out of 104 changed files in this pull request and generated 5 comments.

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src/Avalonia.Controls/TopLevel.cs:665

In HandleClosed, _source is disposed before clearing _source.RootVisual, but clearing the root visual currently updates the renderer/composition root and presentation-source attachment. Because the renderer/layout manager are already disposed, this can throw or leave the visual tree attached. Clear/detach the root visual (and unsubscribe renderer events) before disposing the PresentationSource, and avoid disposing the same layout manager twice (it’s already disposed by _source.Dispose()).

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tests/Avalonia.RenderTests/TestRenderRoot.cs

src/Avalonia.Controls/Platform/InProcessDragSource.cs

src/Avalonia.Controls/PresentationSource/PresentationSource.cs

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Pull request overview

Copilot reviewed 109 out of 109 changed files in this pull request and generated 8 comments.

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src/Avalonia.Base/Rendering/IPresentationSource.cs

src/Avalonia.Controls/PresentationSource/PresentationSource.cs

tests/Avalonia.Base.UnitTests/VisualTests.cs

src/Avalonia.Base/Input/InputElement.cs

src/Avalonia.X11/X11Window.cs

src/Avalonia.Controls/PresentationSource/PresentationSource.Cursor.cs

Copilot · 2026-02-15T21:22:51Z

src/Avalonia.Base/Input/Navigation/XYFocus.FindElements.cs

+        // TODO: The check for bounds is no longer correct
+
+        var root = (InputElement?)element.VisualRoot;
+        if (root == null)
+            return true;

        // Check if the element is within the visible area of the window
        var visibleBounds = new Rect(0, 0, root.Bounds.Width, root.Bounds.Height);


The TODO comment mentions "The check for bounds is no longer correct" but the implementation still relies on this check. The code now uses element.VisualRoot which may no longer be the TopLevel (as per the PR's design changes), making the bounds check against root.Bounds potentially incorrect. This should either be fixed or documented more clearly with a follow-up issue reference.

TODO's from this PR will be addressed in following PRs

src/Avalonia.Controls/ExperimentalAcrylicBorder.cs

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Pull request overview

Copilot reviewed 113 out of 113 changed files in this pull request and generated 12 comments.

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src/Avalonia.Controls/PresentationSource/PresentationSource.cs

src/Avalonia.Base/Input/Navigation/XYFocus.FindElements.cs

Copilot · 2026-02-15T23:39:01Z

src/Avalonia.Controls/PresentationSource/PresentationSource.cs

+    public void Dispose()
+    {
+        _layoutDiagnosticBridge?.Dispose();
+        _layoutDiagnosticBridge = null;
+        LayoutManager.Dispose();
+        Renderer.SceneInvalidated -= SceneInvalidated;
+        // We need to wait for the renderer to complete any in-flight operations
+        Renderer.Dispose();
+
+        PlatformImpl = null;
+        _pointerOverPreProcessor?.OnCompleted();
+        _pointerOverPreProcessorSubscription?.Dispose();
+        if (((IInputRoot)this).PointerOverElement is AvaloniaObject pointerOverElement)
+            pointerOverElement.PropertyChanged -= PointerOverElement_PropertyChanged;
+    }


The PresentationSource.Dispose() method does not set RootVisual to null or call SetPresentationSourceForRootVisual(null) on the current RootVisual. This means that after disposal, the RootVisual may still have a reference to this disposed PresentationSource. This could lead to issues if code tries to access the PresentationSource after disposal. The Dispose method should detach the RootVisual before disposing.

This makes sense, but might currently break TopLevel's assumption about event order, i. e. I think it expects to detach the logical tree before visual tree.

Will need to think more about this in further PRs

src/Avalonia.Controls/TopLevel.cs

src/Avalonia.Base/Visual.cs

src/Avalonia.Base/VisualTreeAttachmentEventArgs.cs

src/Avalonia.Controls/PresentationSource/PresentationSource.Cursor.cs

Copilot · 2026-02-15T23:39:02Z

src/Avalonia.Controls/ToolTipService.cs

+                else if (e.Root.RootElement == _tipControl?.VisualRoot)
                {
                    _lastWindowEventTime = pointerEvent.Timestamp;
                }


The comparison on line 46 checks if e.Root.RootElement equals _tipControl?.VisualRoot. However, RootElement is an InputElement (from IInputRoot.RootElement) while VisualRoot is a Visual? (from the VisualRoot property). These might not be reference-equal even when they represent the same logical root, since RootElement could be a different type. This comparison should likely use TopLevel.GetTopLevel or compare PresentationSource instances instead.

src/Avalonia.Base/Input/Navigation/XYFocus.Impl.cs

src/Avalonia.Controls/ExperimentalAcrylicBorder.cs

kekekeks · 2026-02-16T00:17:06Z

src/Avalonia.Controls/ExperimentalAcrylicBorder.cs

@@ -49,20 +49,29 @@ protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
        {
            base.OnAttachedToVisualTree(e);


This change set seems unrelated, but this code started to trigger compilation errors for me for some reason, so fixed along the way.

avaloniaui-bot · 2026-02-16T01:38:46Z

You can test this PR using the following package version. 12.0.999-cibuild0062267-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

kekekeks · 2026-02-16T07:52:08Z

GH shows commits out of order, 34ac9c9 (the one with green tests) is actually the latest one. This is ready for review, I think

kekekeks · 2026-02-16T07:58:24Z

I have some notes for later. Those aren't super required to be addressed with this PR since TopLevel still always sits at the root of the visual tree.

WindowBase/EmbeddableTopLevelRoot AutomationPeer check Owner == VisualRoot
The PresentationSource.Dispose() method does not set RootVisual to null or call SetPresentationSourceForRootVisual(null) on the current RootVisual. This is currently done in TopLevel to preserve the event ordering. Should probably move to PresentationSource for consistency
XYFocus.FindElements.cs check for bounds won't be correct if TopLevel isn't the root element
Need to do something about X11Window and managed file dialogs, those currently assume that IInputRoot.RootElement is a Window

src/Avalonia.Base/VisualTree/VisualExtensions.cs

src/Avalonia.Base/Visual.cs

MrJul · 2026-02-16T17:41:12Z

src/Avalonia.Base/VisualExtensions.cs

-            var root = visual.VisualRoot ??
-                throw new ArgumentException("Control does not belong to a visual tree.", nameof(visual));
+            var source = visual.PresentationSource;
+            var root = source?.RootVisual ??


Nit: the cast below can now be removed.

MrJul · 2026-02-16T17:45:33Z

src/Avalonia.Base/VisualTreeAttachmentEventArgs.cs

        {
-            Parent = parent ?? throw new ArgumentNullException(nameof(parent));
-            Root = root ?? throw new ArgumentNullException(nameof(root));
+            Debug.Assert(presentationSource.RootVisual != null);


I think the Debug.Assert isn't enough here: this constructor is public. We should check and throw if the presentation source does not have a root visual.

Should we make the ctor private?

I don't think so, let's keep the event args constructible. Checking the state should be enough.

MrJul · 2026-02-16T17:47:09Z

src/Avalonia.Base/VisualTreeAttachmentEventArgs.cs

+        /// The root visual of the tree this visual is being attached to or detached from.
+        /// This is guaranteed to be non-null and will be the same as <see cref="IPresentationSource.RootVisual"/>.
+        /// </summary>
+        public Visual RootVisual => PresentationSource.RootVisual!;


Consider snapshotting the root visual in a field in the constructor. This would allow the event args to be stable even if RootVisual is accessed at a later point (where it could be null).

MrJul · 2026-02-16T18:10:58Z

src/Avalonia.Controls/Platform/InProcessDragSource.cs

            RawDragEvent rawEvent = new RawDragEvent(_dragDrop, type, root, pt, _draggedData!, _allowedEffects, modifiers);
-            var tl = (root as Visual)?.GetSelfAndVisualAncestors().OfType<TopLevel>().FirstOrDefault();
-            tl?.PlatformImpl?.Input?.Invoke(rawEvent);
+            var source = (PresentationSource?)root.RootElement.PresentationSource;


Avoid this cast if possible, as PresentationSource looks safe for the call below.

It's casting from IPresentationSource to PresentationSource, what is wrong with that?

Not assuming the impl, and simply being safe when everything in this chain is?

MrJul · 2026-02-16T18:21:43Z

src/Avalonia.Controls/Primitives/IPopupHost.cs

        void TakeFocus();
+
+        [Obsolete("For unit tests only")]
+        internal IKeyboardNavigationHandler Tests_KeyboardNavigationHandler { get; }


Remove this to keep the interface clean. There's only one use of it in PopupTests where we control the IPopupHost implementation: we can cast to the correct type there.

MrJul · 2026-02-16T18:24:03Z

src/Avalonia.Controls/Remote/Server/RemoteServerTopLevelImpl.cs

        protected virtual Size Measure(Size constraint)
        {
-            var l = (Layoutable) InputRoot!;
+            var l = (Layoutable)InputRoot!.RootElement!;


The Layoutable cast isn't necessary anymore and RootElement is never null.

Note that RootElement will be nullable in subsequent PRs.

MrJul · 2026-02-16T18:30:27Z

src/Avalonia.Controls/NativeControlHost.cs

            var bounds = Bounds;
            // Native window is not rendered by Avalonia
-            var transformToVisual = this.TransformToVisual(_currentRoot);
+            var transformToVisual = _currentRoot.RootVisual != null ? this.TransformToVisual(_currentRoot.RootVisual) : null;


Note: PresentationSource.RootVisual is not nullable, but its implementation accepts null. I read the comment there about keeping it not nullable for now. However, this becomes confusing here: should we expose an additional nullable property for now?

MrJul · 2026-02-16T18:32:53Z

src/Avalonia.Controls/RadioButton.cs


        [MemberNotNull(nameof(_groupManager))]
-        private void EnsureRadioGroupManager(IRenderRoot? root = null)
+        private void EnsureRadioGroupManager(IPresentationSource? source = null)


The parameter should probably be a root visual. Managing the group should have nothing to do with the presentation source.

It was previously managed per-toplevel, so there is no behavior change here.

It's not about the behavioral change, but rather the usage: since the group is scoped to a visual, the presentation source feels like the wrong layer here.

Previously RadioGroupManager was only associated with attached trees, I think it's better to keep it as is

avaloniaui-bot · 2026-02-19T22:18:06Z

You can test this PR using the following package version. 12.0.999-cibuild0062377-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

avaloniaui-bot · 2026-02-19T23:46:16Z

You can test this PR using the following package version. 12.0.999-cibuild0062388-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

kekekeks changed the base branch from master to feature/composition-update-refactor-7 February 6, 2026 10:43

Base automatically changed from feature/composition-update-refactor-7 to master February 6, 2026 11:54

MrJul added enhancement breaking-change wont-backport labels Feb 6, 2026

kekekeks requested a review from Copilot February 15, 2026 20:00

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kekekeks added 8 commits February 16, 2026 01:15

Extracted IInputRoot out of TopLevel

2af8b86

Move some input handling out of TopLevel

14dcc3a

Remove old class, make layout manager private

c81090d

Removed IRenderRoot

0ba1402

Make VisualTreeAttachmentEventArgs a bit more sensible

95604dd

Move ILayoutRoot to PresentationSource

8445428

# Conflicts: # tests/Avalonia.Controls.UnitTests/TabControlTests.cs

Updated some VisualRoot / GetVisualRoot usages

1c41ef7

Updated more XxxRoot usages

5286505

kekekeks force-pushed the feature/presentation-source branch from d1e9aa1 to 5286505 Compare February 15, 2026 20:22

kekekeks requested a review from Copilot February 15, 2026 20:22

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kekekeks added 2 commits February 16, 2026 02:09

More Root usages

668b751

Addressed review

0de7fd1

kekekeks requested a review from Copilot February 15, 2026 21:18

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Hurr-durr xml

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kekekeks marked this pull request as ready for review February 15, 2026 21:22

kekekeks requested a review from MrJul February 15, 2026 21:22

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kekekeks added 2 commits February 16, 2026 02:45

More fixes

de4f620

Maybe fix android compilation

3f7513b

API diff

7a1ca70

kekekeks requested a review from Copilot February 15, 2026 23:34

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kekekeks commented Feb 16, 2026

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kekekeks added 3 commits February 16, 2026 05:55

Yet another cast

7001ae1

I had to use MSIL analysis to detect those casts

34ac9c9

Fixed automation

4e85b02

kekekeks added 5 commits February 16, 2026 04:54

Fix PointerOverPreProcessor

de2d7d5

Fix?

a5a2029

Removed yet another cast to Visual

101dc30

The amount of random downcasts is astonishing

9d09887

Maybe fix mac

c850ed1

MrJul reviewed Feb 16, 2026

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Addressed review

596bf1f

Merge branch 'master' into feature/presentation-source

aeb8ae2

		@@ -49,20 +49,29 @@ protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
		{
		base.OnAttachedToVisualTree(e);

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kekekeks commented Feb 6, 2026 •

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