Fix ImGuiKey mapping for SDL2 and SDL3 by translation method

[eszdman]

As mentioned in #7670, SDL2 partially reports SDL_Keycode as symbols depending on the keyboard layout in SDL initialization. Since ImGui's target is to use translated symbols in en-US layout, I implemented ImGui_ImplSDL_TranslateUntranslatedKey

[ocornut]

It seems like a bug in SDL that you would get e.g. a keycode of 1081 since this doesn't correspond to a SDL_Keycode value in the enumeration. I think you should bring it to SDL to try to get an explanation about it first.

I see that you converted the logic from GLFW, however:

• GLFW has an exception for KEYPAD keys (GLFW_KEY_KP_0 to GLFW_KEY_KP_EQUAL) while your conversion does something differently and technically faulty.
• The result won't be translated keys at all, since it is using scancode names.

There's probably an interesting fallback to use based on scancode, and maybe this is it, but you first need to check with SDL why you are getting those values on your system/setup.

[eszdman]

It seems like a bug in SDL that you would get e.g. a keycode of 1081 since this doesn't correspond to a SDL_Keycode value in the enumeration. I think you should bring it to SDL to try to get an explanation about it first.

I issued SDL with this, it's clearly expected behaviour of SDL_Keycode and enumeration declared only as example on an en-US keyboard libsdl-org/SDL#10002 (comment)