Filtering and Handling Events
#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);
+}