SDL_Delay() while getting events (kinda nooby) - c++

Question

C++, SDL 2
Im making a disco simulator thats just loops through pictures and plays music.
(Epilepsy warning) http://imgur.com/9ePOIAw
Basically I want to run this code
while (isPartying){
currentImage = image1;
SDL_BlitSurface(currentImage, NULL, windowSurface, NULL);
SDL_Delay(25);
SDL_UpdateWindowSurface(window);
currentImage = image2;
SDL_BlitSurface(currentImage, NULL, windowSurface, NULL);
SDL_UpdateWindowSurface(window);
SDL_Delay(25);
currentImage = image3;
SDL_BlitSurface(currentImage, NULL, windowSurface, NULL);
SDL_UpdateWindowSurface(window);
SDL_Delay(25);
//image 3, 4, 5 and so on
}
while getting events all the time.
while (SDL_PollEvent(&ev) != 0){
if (ev.type == SDL_QUIT){
isPartying = false;
}
}
I want it to get events while Im in the middle of the isPartying loop. Now it only checks for events at the beginning (or the end, depends on where I put the event loop of course). Anyone know a better way to wait for the next picture then SDL_Delay()? Or maybe even have another solution
Ano

Answer 1

Basically, what you want to do is to achieve two things at a time.
You have two options:
Using SDL_Thread, but I prefere to not use threads when another solution is possible (because you may have to deal with semaphores or mutexes)
Using SDL_TimerCallback (some would say that too much timers kill the flow of the code, but it's what we gonna use)
Here is a code sample (NB: you must pass SDL_INIT_TIMER to SDL_Init()).
void IsPartying() {
SDL_Event ev;
while (SDL_PollEvent(&ev)){
if (ev.type == SDL_QUIT){
return false;
}
}
return true
}
uint32_t ChangeImage(uint32_t interval, void* param) {
int *imageNb = param;
(*imageNb)++
return interval
}
void Processing() {
// Store your images in SDL_Surface **imageArray
int imageNb = 0;
SDL_TimerID t = SDL_AddTimer(25, ChangeImage, &imageNb);
while (IsPartying()) {
SDL_BlitSurface(imageArray[imageNb], NULL, windowSurface, NULL);
SDL_UpdateWindowSurface(window);
SDL_Delay(1); // Release proc charge
}
SDL_RemoveTimer(SDL_TimerID);
}
Of course you still need to check if you iterated over all the images, else you'll got a nice segfault while trying to access an unallocated cell of the array.