For non-logical scrolling:
- Use 16 for small scroll size (value taken from WPF)
- Use viewport size for large scroll
For logical scrolling, use the `ScrollSize`/`PageScrollSize` defined on `ILogicalScrollable`. Note that this required a small breaking change to `ILogicalScrollable`.
Fixed#3245
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.
And implement the functionality in the content controls themselves. `ContentControlMixin` was too complex and even with its complexity had bugs (such as in #2821). By moving the functionality to the content controls there is some repeated code but it's much more straightforward.
Previously a dangling reference to `ContentPresenter` was left in place in the ex-child control's `InheritanceParent`. When the child is removed from the `ContentPresenter`, reset the value to the control's logical parent.
- Share common layout logic between `Border`, `ContentPresenter` and `ScrollContentPresenter`
- Added a bunch of tests for things not previously convered
- Fix `ScrollContentPresenter` child layout
Added an `IDataTemplateHost` interface with a `IsDataTemplatesInitialized` property to prevent the need for allocating empty `DataTemplates` collections for many controls.
There were two problems:
- There were two root controls (`TestScroller` and `TestRoot`)
- The root control needs to have a fixed size otherwise it will grow because `LayoutManager` passes `MaxClientSize` to its measure (which may be different to the initial measure that we were using to set its size).
Steven Kirk
Benedikt Schroeder
Nikita Tsukanov
Steven Kirk
Andrey Kunchev
Jeremy Koritzinsky
Dan Walmsley
José Pedro