sdl1-peep-hooks.c

/* -*- mode: c; indent-tabs-mode: nil; tab-width: 2
  sdl-fakeqwerty/sdl1-hooks.c
  Copyright 2017 Michael Farrell <micolous+git@gmail.com>
 
  Hook some SDL1.2 related input functionality and make it look like there is a
  QWERTY keyboard attached for applications which read the "sym" (SDL_Keycode).

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#define _GNU_SOURCE
#include <SDL/SDL_events.h>
#include "helper.h"

const char* qwerty_syms = "1234567890-=\0\0qwertyuiop[]\0\0asdfghjkl;'`\0\\zxcvbnm,./";


typedef int (*sig_SDL_PeepEvents)(SDL_Event* event, int numevents, SDL_eventaction action,
                                                                Uint32 mask);

int SDL_PeepEvents(SDL_Event *events, int numevents, SDL_eventaction action,
                                                                Uint32 mask)
{
  int i;
  SDL_Event* event;
  GET_ORIG(SDL_PeepEvents);

  int ret = orig_SDL_PeepEvents(events, numevents, action, mask);
  // There are events which we should try to mangle.
  if (ret > 0) {
    for (int i = 0; i < ret; i++) {
      event = &events[i];
      if (event->type == SDL_KEYDOWN || event->type == SDL_KEYUP) {

        if (event->key.keysym.scancode >= 0x0A && event->key.keysym.scancode <= 0x3d) {
          uint16_t new_sym = (uint8_t)qwerty_syms[event->key.keysym.scancode - 0x0a];

          if (new_sym != 0) {
            event->key.keysym.sym = new_sym;
          }
        }

      }
    }
  }
  return ret;
}