Thank you. That function returns a list of dictionary including 'capture', 'id', 'pattern_id', 'lang', 'metadata' keys. I checked the treesitter help on nvim but not well documented. Do you know which document I should check?

Thank you. It works fine using a interpolated string. Instead of g: variable, is it possible to share a script local variable between functions? Maybe ':help vim9-scopes' says NO.

Thanks. Your idea is nice. I will call timer_start() with something like function(a:callback, [v:event.windows]) so the callback can handle the resized windows.

Thanks. I found it works fine on nvim. But on vim9.0, the lua54.dll can not be loaded and E370 error happens on my Windows 10. Anyway, I will implement it to call v:lua.vim.diff() on my plugin (github.com/rickhowe/diffchar.vim) soon, since the built-in function is so fast.

Because we can use multiple windows on one buffer, by :split command. If there are 2 or more diff mode windows on the same buffer in the tabpage, we need to count as '1' for it.