## What's new?
- Implemented `_TestTooltipWindowController` in the `TestWindowingOwner`
- Fixed how child windows of the main window are rendered in the
application
- Introduced `WindowManager.getChildrenOf` to simplify filtering and
rendering of the children of a parent window
- Added a test for the tooltip window
- Added a test for modal dialogs of the main window
## Pre-launch Checklist
- [X] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [X] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [X] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [X] I signed the [CLA].
- [X] I listed at least one issue that this PR fixes in the description
above.
- [X] I updated/added relevant documentation (doc comments with `///`).
- [X] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [X] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [X] All existing and new tests are passing.
## What's new?
- Implement and test `_window_win32.dart`, the Win32 implementation of
`_window.dart` 🎉
- Wrote a bunch of tests in `window_win32_test.dart` which uses a mock
API barrier to mock the native Win32 layer
- Update `BaseWindowController` to extend `ChangeNotifier` and use it to
inform the `WindowScope` of when things change
- Made `RegularWindowController.empty()` a non-internal constructor, as
it is needed by implementations
- Added a _large_ example application for windowing where users can test
out different windowing concepts and see how they work!
To test, simply run the tests or try out the example app!
## Pre-launch Checklist
- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.
