scrolling/sdl-scrolling.c

   1 /*
   2  * sdl-scrolling - Example program for scrolling images in SDL
   3  *
   4  * Copyright (C) 2013  Antonio Ospite <ospite@studenti.unina.it>
   5  *
   6  * This program is free software: you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation, either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <errno.h>
  21 #include <SDL.h>
  22 #include <SDL_image.h>
  23
  24 #define WIDTH 800
  25 #define HEIGHT 480
  26
  27 #define FPS 30
  28
  29 static int mod(int a, int b)
  30 {
  31         int c = a % b;
  32         return (c < 0) ? c + b : c;
  33 }
  34
  35 static SDL_Surface *load_image(const char *filename)
  36 {
  37         SDL_Surface *image = NULL;
  38         SDL_Surface *optimized_image = NULL;
  39
  40         image = IMG_Load(filename);
  41         if (!image) {
  42                 fprintf(stderr, "IMG_Load: %s\n", IMG_GetError());
  43                 return NULL;
  44         }
  45
  46         optimized_image = SDL_DisplayFormat(image);
  47         if (!optimized_image) {
  48                 fprintf(stderr, "erro whan calling SDL_DisplayFormat().\n");
  49                 return NULL;
  50         }
  51         SDL_FreeSurface(image);
  52
  53         return optimized_image;
  54 }
  55
  56 int main(int argc, char *argv[])
  57 {
  58         int ret;
  59         SDL_Surface* screen = NULL;
  60         SDL_Surface* map = NULL;
  61         SDL_Rect viewport = {0 , 0, WIDTH, HEIGHT};
  62         SDL_Event event;
  63         SDL_Joystick *joystick = NULL;
  64
  65         int running = 1;
  66
  67         Sint16 y_offset = 0;
  68         Sint16 y = 0;
  69         Sint16 lastframe_limit;
  70         Uint32 time_start;
  71         Uint32 time_end;
  72
  73         if (argc != 2) {
  74                 fprintf(stderr, "usage: %s <image>\n", argv[0]);
  75                 return -EINVAL;
  76         }
  77
  78         SDL_Init(SDL_INIT_TIMER | SDL_INIT_JOYSTICK);
  79
  80         screen = SDL_SetVideoMode(WIDTH, HEIGHT, 32, SDL_HWSURFACE);
  81         if (!screen) {
  82                 fprintf(stderr, "Cannot set video mode\n");
  83                 ret = -EINVAL;
  84                 goto out;
  85         }
  86
  87         map = load_image(argv[1]);
  88         if (!map) {
  89                 ret = -EINVAL;
  90                 goto out;
  91         }
  92
  93         lastframe_limit = (map->h - HEIGHT);
  94
  95         if (SDL_NumJoysticks() > 0)
  96                 joystick = SDL_JoystickOpen(0);
  97
  98         SDL_JoystickEventState(SDL_ENABLE);
  99         SDL_EnableKeyRepeat(SDL_DEFAULT_REPEAT_DELAY, SDL_DEFAULT_REPEAT_INTERVAL);
 100
 101         while (running) {
 102                 time_start = SDL_GetTicks();
 103
 104                 while(SDL_PollEvent(&event)) {
 105                         switch(event.type) {
 106                         case SDL_QUIT:
 107                                 running = 0;
 108                                 break;
 109
 110                         case SDL_KEYDOWN:
 111                                 switch(event.key.keysym.sym) {
 112                                 case SDLK_ESCAPE:
 113                                 case SDLK_q:
 114                                         running = 0;
 115                                         break;
 116
 117                                 case SDLK_UP:
 118                                         y_offset += 1;
 119                                         break;
 120
 121                                 case SDLK_DOWN:
 122                                         y_offset -= 1;
 123                                         break;
 124
 125                                 default:
 126                                         printf("key: '%s' keysym: %d\n",
 127                                                SDL_GetKeyName(event.key.keysym.sym),
 128                                                event.key.keysym.sym);
 129                                         break;
 130                                 }
 131                                 break;
 132
 133                         case SDL_JOYAXISMOTION:
 134                                 fprintf(stderr, "Joystick which: %d, axis: %d, value: %d\n",
 135                                         event.jaxis.which, event.jaxis.axis, event.jaxis.value);
 136                                 if (event.jaxis.which == 0) {
 137                                         if (event.jaxis.axis == 0)
 138                                                 /* TODO: improve scaling here */
 139                                                 y_offset = event.jaxis.value;
 140                                 }
 141                         }
 142                 }
 143
 144                 y += y_offset;
 145                 y = mod(y, lastframe_limit);
 146
 147                 viewport.y = y;
 148                 SDL_BlitSurface(map, &viewport, screen, NULL);
 149                 SDL_Flip(screen);
 150
 151                 time_end = SDL_GetTicks();
 152                 if (time_end - time_start < 1000 / FPS)
 153                         SDL_Delay((1000 / FPS) - (time_end - time_start));
 154         }
 155
 156         ret = 0;
 157
 158         if (SDL_JoystickOpened(0))
 159                 SDL_JoystickClose(joystick);
 160
 161         SDL_FreeSurface(map);
 162 out:
 163         SDL_Quit();
 164         return ret;
 165 }