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
Significantly improves the behavior of non-ASCII text input on Windows. Correctly
processes incoming character events as UTF-16, and for now uses UTF-32 for
the text model so that the existing index-based logic will work much more often.
Future work is still needed, but this will handle far more cases correctly.
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.
