Fixes several bugs in the clipboard code, and makes some structural
improvements:
- Adds scoped wrappers for clipboard open/close and global lock/unlock,
to prevent missing cleanup, fixing at least one case where the lock
was not released.
- Adds the relevant window handle to the clipboard calls, since the docs
suggest that some operations won't work without one.
- Adds a missing clear step to setting the clipboard data.
- Switches from TEXT to UNICODETEXT to handle non-ASCII text correctly.
- To enable that, adds UTF-16/-8 conversion utilities built on the
Win32 APIs (rather than the deprecated std::codecvt functions, as
have been previously used in the engine).
- Fixes handling of getting data when the clipboard is empty, correctly
returning null.
- Passes more errors back through the method channel, with details, for
easier debugging of future issues.
Fixes https://github.com/flutter/flutter/issues/54226
The JSON codec is awkward to use in the wrapper (since the client has to build and link one of the JSON libraries to do so). Since it would be very cumbersome to wrap in a C API, and there's essentially no reason to use it instead of the standard codec, this removes it from the wrapper entirely.
Since some system channels (internal to the engine) still use it, it's moved into common/cpp instead of being eliminated entirely. Internally we always use RapidJSON though, so the jsoncpp implementation is removed. Also adds some unit test coverage, since there wasn't any.
Fixes#30669
Start work on flutter/flutter#30726 by adding an alternative win32 shell platform implementation for Windows that is not based on GLFW and that uses LIBANGLE for rendering and native win32 windowing and input. This change does not replace the GLFW implementation but rather runs side by side with it producing a secondary flutter_windows_win32.dll artifact. The following items must be added to attain parity with the GLFW implementation:
- Custom task scheduling
- Support for keyboard modifier keys
- Async texture uploads
- Correct high DPI handling on Windows versions < 1703
and will be added in subsequent changes.
