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  78 >Event Examples</H1
  79 ><P
  80 ></P
  81 ><DIV
  82 CLASS="SECT2"
  83 ><H2
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  85 ><A
  86 NAME="AEN375"
  87 ></A
  88 >Filtering and Handling Events</H2
  89 ><P
  90 ><PRE
  91 CLASS="PROGRAMLISTING"
  92 >#include &#60;stdio.h&#62;
  93 #include &#60;stdlib.h&#62;
  94
  95 #include "SDL.h"
  96
  97 /* This function may run in a separate event thread */
  98 int FilterEvents(const SDL_Event *event) {
  99     static int boycott = 1;
 100
 101     /* This quit event signals the closing of the window */
 102     if ( (event-&#62;type == SDL_QUIT) &#38;&#38; boycott ) {
 103         printf("Quit event filtered out -- try again.\n");
 104         boycott = 0;
 105         return(0);
 106     }
 107     if ( event-&#62;type == SDL_MOUSEMOTION ) {
 108         printf("Mouse moved to (%d,%d)\n",
 109                 event-&#62;motion.x, event-&#62;motion.y);
 110         return(0);    /* Drop it, we've handled it */
 111     }
 112     return(1);
 113 }
 114
 115 int main(int argc, char *argv[])
 116 {
 117     SDL_Event event;
 118
 119     /* Initialize the SDL library (starts the event loop) */
 120     if ( SDL_Init(SDL_INIT_VIDEO) &#60; 0 ) {
 121         fprintf(stderr,
 122                 "Couldn't initialize SDL: %s\n", SDL_GetError());
 123         exit(1);
 124     }
 125
 126     /* Clean up on exit, exit on window close and interrupt */
 127     atexit(SDL_Quit);
 128
 129     /* Ignore key events */
 130     SDL_EventState(SDL_KEYDOWN, SDL_IGNORE);
 131     SDL_EventState(SDL_KEYUP, SDL_IGNORE);
 132
 133     /* Filter quit and mouse motion events */
 134     SDL_SetEventFilter(FilterEvents);
 135
 136     /* The mouse isn't much use unless we have a display for reference */
 137     if ( SDL_SetVideoMode(640, 480, 8, 0) == NULL ) {
 138         fprintf(stderr, "Couldn't set 640x480x8 video mode: %s\n",
 139                         SDL_GetError());
 140         exit(1);
 141     }
 142
 143     /* Loop waiting for ESC+Mouse_Button */
 144     while ( SDL_WaitEvent(&#38;event) &#62;= 0 ) {
 145         switch (event.type) {
 146             case SDL_ACTIVEEVENT: {
 147                 if ( event.active.state &#38; SDL_APPACTIVE ) {
 148                     if ( event.active.gain ) {
 149                         printf("App activated\n");
 150                     } else {
 151                         printf("App iconified\n");
 152                     }
 153                 }
 154             }
 155             break;
 156
 157             case SDL_MOUSEBUTTONDOWN: {
 158                 Uint8 *keys;
 159
 160                 keys = SDL_GetKeyState(NULL);
 161                 if ( keys[SDLK_ESCAPE] == SDL_PRESSED ) {
 162                     printf("Bye bye...\n");
 163                     exit(0);
 164                 }
 165                 printf("Mouse button pressed\n");
 166             }
 167             break;
 168
 169             case SDL_QUIT: {
 170                 printf("Quit requested, quitting.\n");
 171                 exit(0);
 172             }
 173             break;
 174         }
 175     }
 176     /* This should never happen */
 177     printf("SDL_WaitEvent error: %s\n", SDL_GetError());
 178     exit(1);
 179 }</PRE
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