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guideeventexamples.html
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>Filtering and Handling Events</H2
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CLASS="PROGRAMLISTING"
>#include <stdio.h>
#include <stdlib.h>
#include "SDL.h"
/* This function may run in a separate event thread */
int FilterEvents(const SDL_Event *event) {
static int boycott = 1;
/* This quit event signals the closing of the window */
if ( (event->type == SDL_QUIT) && boycott ) {
printf("Quit event filtered out -- try again.\n");
boycott = 0;
return(0);
}
if ( event->type == SDL_MOUSEMOTION ) {
printf("Mouse moved to (%d,%d)\n",
event->motion.x, event->motion.y);
return(0); /* Drop it, we've handled it */
}
return(1);
}
int main(int argc, char *argv[])
{
SDL_Event event;
/* Initialize the SDL library (starts the event loop) */
if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
fprintf(stderr,
"Couldn't initialize SDL: %s\n", SDL_GetError());
exit(1);
}
/* Clean up on exit, exit on window close and interrupt */
atexit(SDL_Quit);
/* Ignore key events */
SDL_EventState(SDL_KEYDOWN, SDL_IGNORE);
SDL_EventState(SDL_KEYUP, SDL_IGNORE);
/* Filter quit and mouse motion events */
SDL_SetEventFilter(FilterEvents);
/* The mouse isn't much use unless we have a display for reference */
if ( SDL_SetVideoMode(640, 480, 8, 0) == NULL ) {
fprintf(stderr, "Couldn't set 640x480x8 video mode: %s\n",
SDL_GetError());
exit(1);
}
/* Loop waiting for ESC+Mouse_Button */
while ( SDL_WaitEvent(&event) >= 0 ) {
switch (event.type) {
case SDL_ACTIVEEVENT: {
if ( event.active.state & SDL_APPACTIVE ) {
if ( event.active.gain ) {
printf("App activated\n");
} else {
printf("App iconified\n");
}
}
}
break;
case SDL_MOUSEBUTTONDOWN: {
Uint8 *keys;
keys = SDL_GetKeyState(NULL);
if ( keys[SDLK_ESCAPE] == SDL_PRESSED ) {
printf("Bye bye...\n");
exit(0);
}
printf("Mouse button pressed\n");
}
break;
case SDL_QUIT: {
printf("Quit requested, quitting.\n");
exit(0);
}
break;
}
}
/* This should never happen */
printf("SDL_WaitEvent error: %s\n", SDL_GetError());
exit(1);
}</PRE
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