linuxdevellinuxdevel/Avalonia-skills/skills/avalonia/avalonia-versions/SKILL.md

avalonia-versions

Skill50 starsChanged 9 days agoMITView on GitHub

Use FIRST when the Avalonia version matters — detecting which Avalonia version a project uses, checking whether a feature/API exists in 11.3, 12.0 or 12.1, migrating 11.x → 12.x, or upgrading 12.0 → 12.1. Contains the version/feature matrix, renamed/removed API tables, and the version-label conventions used by all other Avalonia skills.

In this repository23 other files it gives its agents.
- avalonia-app-developmentSkill
- avalonia-controlsSkill
- avalonia-custom-controlsSkill
- avalonia-data-bindingSkill
- avalonia-data-templatesSkill
- avalonia-deploymentSkill
- avalonia-eventsSkill
- avalonia-graphics-animationSkill
- avalonia-input-interactionSkill
- avalonia-interop-renderingSkill
- avalonia-layoutSkill
- avalonia-mobileSkill
- avalonia-mvvmSkill
- avalonia-performanceSkill
- avalonia-pro-maxSkill
- avalonia-property-systemSkill
- avalonia-servicesSkill
- avalonia-stylingSkill
- avalonia-testingSkill
- avalonia-threadingSkill
- avalonia-wpf-migrationSkill
- avalonia-xamlSkill
- avaloniaSkill

The file

We split this skill into the rules it gives an agent

3 rules. About 0 are common, 1 is distinctive, and 2 are very specific to this project.

≈0
Common · estimate
Many files like this have a rule of this kind.
≈1
Distinctive · estimate
This author's own choices. Worth a look.
2
Very specific
Tied to their project's names, files or tools. Probably skip.

Common
Distinctive
Very specific

Distinctive:
Before writing code, find the version.
line 19
Very specific:
No project yet → use 12.1.x (latest patch), net10.0.
line 30
Very specific:
When a skill shows a 12.x API and an (11.x) alternative side by side, pick the one that matches the project's version.
line 43

≈ “Common” is an estimate: at least 1 in 5 of the 350,495 skill files we read have a rule of the same kind, not the same words. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.

Keep what fits and drop the rest. Your version, ready for your agents.

Files

SKILL.md

Avalonia Versions & Feature Matrix

Supported Versions

Line	Latest patch	Released	.NET	Status
12.1	12.1.4	12.1.0: Jul 2026	net8.0+ (net10.0 recommended; required for Android/iOS)	Current stable — default for new projects
12.0	12.0.5	12.0.0: Apr 2026	same as 12.1	Supported — drop-in upgrade to 12.1
11.3	11.3.22	—	netstandard2.0 / net6.0+ / .NET Framework	Legacy — maintenance only; plan migration

Versions older than 11.3 are out of scope; treat them like 11.3 but expect missing APIs.

Step 1 — Detect the Project's Version

Before writing code, find the version. Search in this order:

Directory.Packages.props → <PackageVersion Include="Avalonia" Version="..."/>
*.csproj → <PackageReference Include="Avalonia" Version="..."/>
Directory.Build.props → an AvaloniaVersion property or similar
dotnet list package | grep -i avalonia

grep -rhoE 'Include="Avalonia(\.Desktop)?" Version="[^"]+"' --include='*.csproj' --include='*.props' .

No project yet → use 12.1.x (latest patch), net10.0.
Mixed versions across Avalonia.* packages → bug. All core Avalonia.* packages must share one version (third-party themes/controls have their own versioning).
ReactiveUI.Avalonia, Avalonia.Controls.WebView, Avalonia.Controls.DataGrid, Avalonia.Controls.TreeDataGrid version on their own schedule; check NuGet for the release that matches the core version.

Version Label Convention (used across all skills)

Label	Meaning
(12.0+)	Exists from 12.0.0 onward. Not in 11.x
(12.1+)	Exists from 12.1.0 onward. Not in 12.0 or 11.x
(11.x)	11.x API — removed/obsolete in 12. Only use in 11.x projects
no label	Works in 11.3, 12.0 and 12.1

When a skill shows a 12.x API and an (11.x) alternative side by side, pick the one that matches the project's version. Never mix — e.g. don't use DataObject in a 12.x project.

Feature Matrix

✅ available · ❌ not available · ⚠️ obsolete (works, warns) · 🧪 experimental

Platform & runtime

Feature	11.3	12.0	12.1
.NET Framework / netstandard2.0 targets	✅	❌	❌
net8.0 minimum, net10.0 recommended	—	✅	✅
Android/iOS on net10.0 (required)	❌	✅	✅
Mac Catalyst (via `Avalonia.iOS`)	❌	✅	✅
iOS scene delegate	❌	✅	✅
Rebuilt Android backend, multiple activities, `IActivityApplicationLifetime`	❌	✅	✅
Android system-theme change detection	❌	❌	✅
Linux AT-SPI2 accessibility	❌	✅	✅
Native Wayland backend (`Avalonia.Wayland` + `.UseWayland()`)	❌	❌	🧪 (not picked by `UsePlatformDetect()`)
X11 drag-and-drop between processes (XDND)	❌	❌	✅
X11/Windows render at monitor refresh rate (>60 FPS)	❌	❌	✅
Embed Avalonia in WinUI 3 (`Avalonia.WinUI`)	❌	❌	✅
Windows 11 window corner rounding control	❌	❌	✅
`Avalonia.Direct2D1` backend	✅	❌ (use Skia)	❌
`Avalonia.Browser.Blazor`, `Avalonia.Tizen`	✅	❌	❌
SBOM shipped with packages	❌	❌	✅

Controls

Control / feature	11.3	12.0	12.1
`GroupBox`	❌	✅	✅
`PipsPager`	❌	✅	✅
Page-based navigation (`Page`, `ContentPage`, `NavigationPage`, `TabbedPage`, `DrawerPage`, `CarouselPage`, `CommandBar`)	❌	✅	✅
`TableView` (read-only tabular, virtualized)	❌	❌	✅
`NativeWebView` / `NativeWebDialog` open source (`Avalonia.Controls.WebView`) — Windows, macOS, Linux, iOS; Android experimental; not browser/WASM	❌ (commercial)	✅	✅
`DataGrid` (`Avalonia.Controls.DataGrid`)	✅	✅	✅ maintenance mode — prefer `TableView`/`TreeDataGrid` for new read-only grids
`TreeDataGrid` (`Avalonia.Controls.TreeDataGrid`) — needs Avalonia Accelerate licence since 11.2.0; 12.x packages need Avalonia ≥ 12.0.1	✅ (11.x pkg)	✅	✅
`TextBox.PlaceholderText` / `UseFloatingPlaceholder`	❌	✅	✅
`TextBox.Watermark` / `UseFloatingWatermark`	✅	⚠️	⚠️
`PlaceholderForeground` (TextBox, AutoCompleteBox, CalendarDatePicker, NumericUpDown)	❌	✅	✅
`TabItem.IconTemplate`	❌	✅	✅
`FlyoutBase.IsOpen` styled property	❌	✅	✅
Carousel gestures + `WrapSelection`	❌	✅	✅
`DrawingImage.Viewbox`	❌	✅	✅
`NativeDock.Menu` (macOS dock menu)	❌	✅	✅
`WindowDrawnDecorations` (themeable client-side decorations)	❌	✅	✅
`Window.WindowDecorations`	❌	✅	✅
`Window.SystemDecorations` / `ExtendClientAreaChromeHints`	✅	⚠️ / ❌	⚠️ / ❌

Bindings, text, input, threading

Feature	11.3	12.0	12.1
Compiled bindings on by default (`AvaloniaUseCompiledBindingsByDefault` defaults `true`)	❌ (opt-in)	✅	✅
`CompiledBinding.Create(...)` from LINQ expressions	❌	✅	✅
Binding plugins (`BindingPlugins`) configurable	✅	❌ removed	❌
Data-annotations validation on by default	✅	❌ (opt-in)	❌
`TextOptions` (`TextRenderingMode` etc.)	❌	✅	✅
`TextElement.LetterSpacing` (inherited)	❌ (`TextBlock.LetterSpacing`)	✅	✅
`UseHarfBuzz()` required with explicit `UseSkia()`	❌	✅	✅
Access keys match printed symbol (accents, digits)	❌	✅	✅
Focus Traversal API (`IFocusManager.FindNextElement`/`TryMoveFocus`), cancellable focus, `FocusChangedEventArgs`	❌	✅	✅
Gesture events directly on `InputElement` (no `Gestures.` prefix)	❌	✅	✅
Touch/pen select on release (not press)	❌	✅	✅
`Dispatcher.CurrentDispatcher`, `Dispatcher.FromThread`, `AvaloniaObject.Dispatcher`, `Dispatcher.Yield`	❌	✅	✅
Async clipboard/drag-drop (`IAsyncDataTransfer`, `DataTransfer`)	❌	✅	✅
`PlatformFeedback` (haptics/sound, Android/iOS)	❌	❌	✅
Hidden controls stop style animations (`PlaybackBehavior="Always"` to override)	❌	✅	✅

11.x → 12.0 Migration: Renamed / Replaced APIs

11.x	12.x
`IDataObject` / `DataObject`	`IAsyncDataTransfer` / `DataTransfer` + `DataTransferItem`
`DataFormats.Text` etc.	`DataFormat.Text` etc.
`DragDrop.DoDragDrop(...)`	`await DragDrop.DoDragDropAsync(...)`
`DragEventArgs.Data`	`DragEventArgs.DataTransfer`
`IClipboard.GetTextAsync` / `SetTextAsync`	`TryGetTextAsync` / `SetTextAsync` (extension methods, `ClipboardExtensions`)
`IClipboard.SetDataObjectAsync` / `GetDataAsync` / `GetFormatsAsync`	`SetDataAsync` / `TryGetDataAsync` / `GetDataFormatsAsync`
`IBinding` / `InstancedBinding`	`BindingBase` / `BindingExpressionBase`
`new Binding(...)` in C#	`ReflectionBinding` or `CompiledBinding`
`GotFocusEventArgs`	`FocusChangedEventArgs`
`KeyboardNavigationHandler.GetNext`	`IFocusManager.FindNextElement(...)` / `TryMoveFocus(...)`
`Gestures.Pinch="..."` etc. in XAML	`Pinch="..."`
`TopLevel.PlatformSettings`	`visual.GetPlatformSettings()`
`VisualExtensions.GetVisualRoot`	`GetPresentationSource()` → `.RootVisual`
`(TopLevel)visual.GetVisualRoot()`	`TopLevel.GetTopLevel(visual)`
`SystemDecorations` / `ExtendClientAreaChromeHints`	`WindowDecorations`
`Chrome.TitleBar`, `CaptionButtons`, `ChromeOverlayLayer`	`WindowDrawnDecorations`
`VisualLayerManager.AdornerLayer` / `OverlayLayer`	`AdornerLayer.GetAdornerLayer(v)` / `OverlayLayer.GetOverlayLayer(v)`
`TextBox.Watermark` / `UseFloatingWatermark`	`PlaceholderText` / `UseFloatingPlaceholder`
`RenderOptions.TextRenderingMode`	`TextOptions.TextRenderingMode`
`TextBlock.LetterSpacing`	`TextElement.LetterSpacing`
`AccessText.AccessKey` (`char`)	`string?`
`NativeMenuItemToggleType`	`MenuItemToggleType`
`AvaloniaMainActivity<TApp>`	`AvaloniaMainActivity` + `[Application] class App : AvaloniaAndroidApplication<TApp>`
`ISingleViewApplicationLifetime` (Android)	`IActivityApplicationLifetime` with `MainViewFactory` (iOS/Browser still use `ISingleViewApplicationLifetime`)
`Avalonia.Diagnostics` + `AttachDevTools()`	`AvaloniaUI.DiagnosticsSupport` + `AttachDeveloperTools()`
`Avalonia.ReactiveUI` package (deprecated on NuGet, last 11.3.8)	`ReactiveUI.Avalonia` package (maintained by ReactiveUI team)
`Avalonia.Direct2D1` / `UseDirect2D1()`	`UseSkia()`
xUnit v2 / NUnit 3 (with `Avalonia.Headless.*`)	xUnit v3 / NUnit 4
`FuncMultiValueConverter` lambda `IEnumerable<TIn>`	`IReadOnlyList<TIn>`
`ResourcesChangedEventArgs.Empty` / `new(...)`	`ResourcesChangedEventArgs.Create(...)` (now a struct)

Removed in 12 (were obsolete in 11)

OpenFileDialog/SaveFileDialog/OpenFolderDialog/SystemDialog → IStorageProvider · ToggleButton.Checked/Unchecked/Indeterminate events → IsCheckedChanged · Popup.PlacementMode/ContextMenu.PlacementMode → Placement · CubicBezierEasing → SplineEasing · CustomAnimatorBase → InterpolatingAnimator<T> · ItemContainerGenerator.ContainerFromIndex → ItemsControl.ContainerFromIndex · BindingPriority.TemplatedParent → Template · DrawingContext.PushPreTransform/PushPostTransform → PushTransform · RadialGradientBrush.Radius → RadiusX/RadiusY · Screen.PixelDensity → Scaling · Screen.Primary → IsPrimary · IStyleable → StyledElement · IActivatableApplicationLifetime → TryGetFeature<IActivatableLifetime>() · IInsetsManager.DisplayEdgeToEdge → DisplayEdgeToEdgePreference · TopLevel.PointerOverElement (no replacement) · TextInputMethodClient.ShowInputPanel → InputPaneActivationRequested event · Type 1 fonts · BinaryFormatter clipboard on Windows.

Behavior changes in 12 (no compile error — silent!)

Compiled bindings on by default: {Binding} without x:DataType now fails to compile. Add x:DataType, or use {ReflectionBinding}, or set <AvaloniaUseCompiledBindingsByDefault>false</...>.
Data-annotation validation off by default. Properties registered with enableDataValidation: true report errors automatically.
Touch/pen: selection/focus on pointer release. ListBoxItem/TreeViewItem handle selection themselves (no bubbling to ItemsControl).
Window.WindowState is a direct property — cannot be set from a style.
Style-triggered animations pause on invisible controls — set Animation.PlaybackBehavior="Always" to keep ticking.
Dispatcher.InvokeAsync captures ExecutionContext (AsyncLocal, culture flow).
DispatcherTimer / AvaloniaSynchronizationContext use the current dispatcher, not always the UI thread — create timers on the UI thread.
Explicit UseSkia() without UseHarfBuzz() → InvalidOperationException: No text shaping system configured. (UsePlatformDetect() handles this.)
Windows ExtendClientAreaToDecorationsHint fixed — remove old margin workarounds.

12.0 → 12.1 Upgrade

Drop-in: bump all Avalonia.* to 12.1.x. No API breaks. Notes:

Multiple dirty-rect clipping now off by default; stencil buffers on by default (more HW-accelerated clipping).
Apps now render at monitor refresh rate on X11 (and Windows with non-default render modes) — animations that assumed 60 FPS ticks still work (time-based), but CPU/GPU use may rise.
Wayland is opt-in and experimental: AppBuilder.Configure<App>().UseWayland() with Avalonia.Wayland; keep UsePlatformDetect() as default.

Common Mistakes

Writing 12.x API (DataTransfer, PlaceholderText, GroupBox) into an 11.x project, or 11.x API into 12.x — check version first.
Upgrading Avalonia but not Avalonia.Desktop/Avalonia.Themes.Fluent/Avalonia.Headless.* — all must match.
Keeping Avalonia.ReactiveUI / Avalonia.Diagnostics after moving to 12 — they don't exist for 12.
Forgetting net10.0 on Android/iOS heads in 12.x.
Assuming UsePlatformDetect() picks Wayland in 12.1 — it doesn't.

Sources

Breaking changes: https://docs.avaloniaui.net/docs/avalonia12-breaking-changes
12.0.0 release notes: https://github.com/AvaloniaUI/Avalonia/discussions/21091
What's new in 12.1: https://avaloniaui.net/blog/release-12-1
Package versions: https://www.nuget.org/packages/Avalonia

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