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I'm building a game using SDL in Linux platform.

Now I want to read user input with SDL_GetKeyboardState, but my doubt is wich is the best way using a thread or a timer.

I tried both and I think they work well.

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IMO you got a problem here if an event poller eats up 100% CPU. What's your framerate? Do you have a small Sleep(2) in the mail loop? SDL can be really slow if you don't convert all graphics to the screen resolution but an event handler taking CPU speed seems weird. –  Valmond Oct 1 '14 at 8:48
    
If you use double buffering the buffer swap at the end of the frame will block until the swap is allowed to happen. So when you have v-sync on you will save CPU there –  bogglez Oct 1 '14 at 13:46

1 Answer 1

up vote 0 down vote accepted

If you have uncapped FPS, it should eat 100% of your CPU, but most probably you want cap FPS at some reasonable value, say 60 fps, basic implementation can be as follows:

const unsigned int FPS = 60;
const unsigned int DELAY_TIME = 1000 / FPS;
unsigned int frameStart, frameTime;
int spareTime;

// your main loop
while (bRunning) {
    frameStart = SDL_GetTicks();

    // do your stuff

    frameTime = SDL_GetTicks() - frameStart;
    spareTime = DELAY_TIME - frameTime;
    if (spareTime > 0) {
        SDL_Delay((unsigned int)spareTime);
    }
}
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Yes, already know that I have to put a delay to get the desired Fps, but I want to read keyboard apart from the main loop so my question was wich is better a thread o timer? –  Luis Rossell Oct 1 '14 at 12:31
    
@LuisRossell well, I thought your main concern was about 100% CPU time, not the polling itself. If that is not concern, you could remove that information from the question. –  Petr Abdulin Oct 1 '14 at 15:23
    
Yes, you're right it's unclear, thanks for code snippet –  Luis Rossell Oct 1 '14 at 17:13
    
@LuisRossell you shouldn't mark it as answer though, just upvote if you found it useful. –  Petr Abdulin Oct 2 '14 at 1:34

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