- accessibility
- localization
- text rendering
- input methods
- widget toolkit
- event loop
- HIG
The document should also contain example code for something basic for every platform. All this information could be then used to create the Right Thing Toolkit.
Probably it should aim for the future. So only include APIs that most probably would not be deprecated in 5 years. The platforms that I'm thinking about: Android, Freedesktop/Unix-like, iOS, macOS and Windows.
I was wondering what is current situation with Windows. Is UWP the future or will it be soon replaced by yet another API? Is side-loading currently as effortless as running of Win32 apps? Or maybe Win32 is good enough, because they will always support it?
[0] as opposed to the Worse is Better, because that's current situation and it's not all that hard, use SDL or whatever and draw everything yourself.