The validating layer introduced in #7369 has done its job and caught a few bugs, but was causing difficulties in certain places so removing it now.
Fixes#7573
#7369 introduced a validating layer over `WindowBase.PlatformImpl` that is only enabled in debug mode. This validating layer was causing unit tests to fail in debug mode but not on CI which runs tests in release mode.
Fix the problems:
- `PopupRoot` was not correctly disposing itself on `Dispose` - make it call `HandleClosed` in order to perform the same steps as when the popup is closed via other means
- Some unit tests try to access the `PlatformImpl` to get hold of a mock. Added `ValidatingWindowImpl.Unwrap` to allow this
- `ValidatingWindowBaseImpl.Activated` was setting the wrong property on the wrapped `PlatformImpl`.
- Adds a "resize reason" to platform `Resized` events
- Which is used by the auto-sizing code to determine whether to reset `SizeToContent`
- Also other improvements to the reset logic for `SizeToContent`:
- Don't reset it if the size hasn't changed
- Don't reset it if `CanResize == false`
- Only reset the dimensions whose size has changed
- Obsolete the `BeginAutoSizing`/`AutoSizing` feature in `WindowBase`
- Renamed `MaxClientSize` to `MaxAutoSizeHint`
- On Windows get its value from `WM_GETMINMAXINFO` message
- Remove `ILayoutRoot.MaxClientSize` as it's not used any more
Top-level controls cannot have a `Bounds` offset, and their `(Min)/(Max)/Width` and `(Min)/(Max)/Height` reflects the client size of the actual window, so don't need to be applied at the layout level.
Fixes#3784
Simon Cropp
Steven Kirk
Dan Walmsley
Giuseppe Lippolis
Dariusz Komosinski
Nikita Tsukanov
Steven Kirk
José Pedro
Benedikt Schroeder