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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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