How to correctly handle control-key combinations in SDL2 - keyboard-events

Question

In my SDL 2.0 based application, I would like to handle both Control + and Control =.
I understand that I could handle the SDL_KEYDOWN event and look for the SDLK_EQUALS keycode in combination with KEYMODE_CTRL. And even check for KEYMOD_SHIFT' to distinguish between+and=`. However, this is not portable and breaks on keyboards where those symbols are mapped to different keys.
Another thing I have tried is to enable SDL_StartTextInput() and then listen to SDL_TEXTINPUT events. However that only works for printable characters. It ignores control sequences completely.
What is the correct the way to do this? I see SDL 1.2 actually had a unicode field in the SDL_Keysym structure. That would definitely make this a lot easier for me. Does anyone know why that was removed and what the equivalent in SDL 2.0 would be?

Answer 1

Here is an example how you can get unicode input as SDL_TEXTINPUT but the rest as SDL_KEYDOWN:
#include "SDL.h"
#include <stdio.h>
int main(int argc, char *argv[]) {
int done = 0;
SDL_Init(SDL_INIT_VIDEO);
SDL_Window *w = SDL_CreateWindow("foo", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
640, 480, 0);
int lctrl = 0, rctrl = 0;
SDL_StartTextInput();
while (!done) {
SDL_Event event;
while(SDL_PollEvent(&event)) {
switch (event.type) {
case SDL_QUIT:
done = 1;
break;
case SDL_TEXTINPUT: {
int ctrl_state = lctrl || rctrl;
printf("%s, ctrl %s\n", event.text.text, (ctrl_state) ? "pressed" : "released");
} break;
case SDL_KEYDOWN:
if(event.key.keysym.sym == SDLK_RCTRL) { rctrl = 1; }
else if(event.key.keysym.sym == SDLK_LCTRL) { lctrl = 1; }
break;
case SDL_KEYUP:
if(event.key.keysym.sym == SDLK_RCTRL) { rctrl = 0; }
else if(event.key.keysym.sym == SDLK_LCTRL) { lctrl = 0; }
break;
}
}
SDL_UpdateWindowSurface(w);
}
SDL_Quit();
return 0;
}
To simplify things, it ignores SDL_TEXTEDITING, which may (or not) be what you want. Also SDL_GetKeyboardState can be used instead of manually processing events and accumulating modifier keys flags, with the same result.