Support OS language switch

[habamax]

Currently when I try to switch language and input some russian text I get something different.
And then If I switch back to english it continues "weirdness":

[habamax]

Probably related to #125

[Kethku]

I would love some advice for how best to solve this. I'm incredibly frustrated with my options at the moment.

The full backstory is long and tired, but the basic gist is that sdl2 (the cross platform windowing library I am using) has two modes for getting keyboard inputs:

Keydown/KeyUp which gets non keyboard mapped keycodes. This event lets allows me to tell which key is pressed and which modifiers are held down, but does not transform the key to the correct keyboard layout mapped value. As an example: ctrl-shift-6 on a qwerty keyboard would be reported as ctrl-shift-6 using this method instead of ctrl-^.

TextInput which transforms the key properly, but does not allow for modifiers that don't produce a unique value. As an example: shift-6 on qwerty would properly produce ^, but ctrl-shift-6 would produce no TextInput event.

Given these two primitives, today neovide does the following here https://github.com/Kethku/neovide/blob/master/src/bridge/layouts/mod.rs#L102

If TextInput produced a text value, then shift is ignored (it is assumed that the textinput used it up), and modifiers are applied.
If not, we look up the keyboard layout configured by the neovide_keyboard_layout global variable (currently there is one qwerty option, but as demand requires more will be added) and we manually modify the keyboard character to produce the correct value. This may consume shift, ctrl, and or alt modifiers in the process.

This strategy is very unfortunate because it requires the user to set the correct keyboard layout in a global variable and it requires us to list every possible key combination in a giant file for every supported layout which is decidedly not crossplatform or layout compatible. If a user has a novel layout, they have to contribute it to the repo or they are out of luck.

Unfortunately I don't currently see a way out of this. I would LOVE any hint or advice for how to fix this. At this point I'm out of ideas.

[Kethku]

As for the exact issue here, the D- means that the windows key is held down. I believe this is fixed in the current master, but not the released version of the app. Please build from source

[habamax]

Looks like you use kind of "scan codes" instead of characters and I am not sure if there is a simple/easy way to get real chars out of scan codes.

So I can see the following routes:

• do nothing (then users with non-latin layouts wouldn't use neovide that much)
• implement neovide specific keyboard layout manager and database of layouts -- I am not sure about efforts, but looks like huge.
• refactor keyboard input routines to use chars instead of scancodes (I believe (g)vim and neovim(-qt) use characters) -- the efforts..., well :)

Not sure if SDL has char input you can use: https://forums.libsdl.org/viewtopic.php?p=51153

[Kethku]

The character input is handled by the TextInput events I described. These can't be used for everything because they are not raised if modifiers outside of those necessary for producing the initial character are held down. So shift-6 produces ^ but ctrl-shift-6 does not.

[habamax]

Sorry not an expert :(, and don't know rust

But if I press C-S-6 shouldn't it go here:

https://github.com/Kethku/neovide/blob/e9808f185ff103e7e3dc2361bc5238541ccbc3e7/src/bridge/layouts/mod.rs#L103

Like, ^ was generated by S-6 and then you apply CTRL modifier?

[Kethku]

It doesn't. No textinput event is raised because of a limitation in sdl2. I brought up the issue with the sdl2 team and they ignored my concerns even with repeated attempts to describe the problem. So at this point I'm out of luck

[Kethku]

For background this is the conversation I had: https://bugzilla.libsdl.org/show_bug.cgi?id=5029

[ewhac]

This issue also breaks using C-^ to switch to the "alternate" file, something I use a lot.

[Kethku]

closing in favor of #445