The root of our logical tree is denoted by `IStyleRoot` for historical reasons: before #1594, styling was defined in `Avalonia.Styling` but the logical tree was defined in `Avalonia.Controls`. The styling system needed a root but because it was lower-level than the logical tree it had to define its own root type which was then repurposed for use by the logical tree.
Since #1594 the logical tree is defined in `Avalonia.Styling` as well so we might as well call `IStyleRoot` what it is: the logical tree root.
- When detaching set `Parent` to `null` before raising the `DetachedFromLogicalTree` event
- To do this, we need to store the logical root in the control so that e.g. a child control can be detached in a `DetachedFromLogicalTree` handler
- Add `Source` and `Parent` properties to `LogicalTreeAttachmentEventArgs` to give more context on what caused the attachment/detachment
Update `TreeItemContainerGenerator.Index` when a `TreeViewItem` is added to or removed from the logical tree. This ensures that removed `TreeViewItem`s won't try to add duplicate containers to the index.
Fixes#2985
- Added `IInputRoot Root` property to `RawInputEventArgs`
- Removed `InputRoot` and `Root` properties from `RawDragEvent` and `RawPointerEvent` as its now in the base class
- `InputRoot` in `RawDragEvent` was incorrectly using the type `IInputElement` instead of `IInputRoot`, fix callers that were using the wrong type
- Pass the input root to all raw input event constructors
- If no control is focused in `KeyboardDevice.ProcessRawEvent` then raise the event on the root
Steven Kirk
Dariusz Komosiński
Jumar Macato
Dan Walmsley
Benedikt Schroeder
Andrey Kunchev
Nikita Tsukanov
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