SDL Performance problem

This is a discussion on SDL Performance problem within the Game Programming forums, part of the General Programming Boards category; This runs fine in that the red dot is drawn at (10, 10) but it's slooooow. As it is loaded ...

  1. #1
    Supermassive black hole cboard_member's Avatar
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    SDL Performance problem

    This runs fine in that the red dot is drawn at (10, 10) but it's slooooow. As it is loaded up you can see it appearing in the start bar really slowly and if I move the window it leaves copies all over the place.

    Code:
    #include <SDL/SDL.h>
    #define WIN32_LEAN_AND_MEAN
    #include <windows.h>
    
    bool SDLInitialise();
    void RenderFrame();
    void DrawPixel(int x, int y, unsigned int color);
    
    SDL_Surface *sdlsBackBuffer = NULL;
    unsigned int *BBWrite = NULL;
    
    int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
    {
        SDL_Event sdlEvent;
        bool bDone = false;
    
        SDLInitialise();
    
        while (! bDone)
        {
            RenderFrame();
    
            while (SDL_PollEvent(&sdlEvent))
            {
                switch (sdlEvent.type)
                {
                case SDL_KEYUP:
                    if (sdlEvent.key.keysym.sym == SDLK_ESCAPE)
                        bDone = true;
    
                case SDL_QUIT:
                    bDone = true;
                }
            }
        }
    
        return 0;
    }
    
    // SDLInitialise
    //
    bool SDLInitialise()
    {
        if (SDL_Init(SDL_INIT_VIDEO) != 0)
            return false;
    
        atexit(SDL_Quit);
    
        sdlsBackBuffer = SDL_SetVideoMode(800, 600, 32, SDL_SWSURFACE);
        if (sdlsBackBuffer == NULL)
            return false;
    
        BBWrite = static_cast<unsigned int *> (sdlsBackBuffer->pixels);
        return true;
    }
    
    // RenderFrame
    //
    void RenderFrame()
    {
        if (SDL_MUSTLOCK(sdlsBackBuffer))
            if (SDL_LockSurface(sdlsBackBuffer) < 0)
                return;
    
        DrawPixel(10, 10, 0xff0000);
    
        if (SDL_MUSTLOCK(sdlsBackBuffer))
            SDL_UnlockSurface(sdlsBackBuffer);
        SDL_UpdateRect(sdlsBackBuffer, 0, 0, 800, 600);
    }
    
    // DrawPixel
    //
    void DrawPixel(int x, int y, unsigned int color)
    {
        unsigned ofs = y * (sdlsBackBuffer->pitch / 4);
        *(BBWrite + ofs + x) = color;
    }
    Is there anything drastically wrong here or does it always do this?
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

  2. #2
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    How dose it work in full screen mode? I never tried it in windowed mode but it used to run fine for me in fullscreen mode.

  3. #3
    Supermassive black hole cboard_member's Avatar
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    It seems to run better except it also seems to throw the y * screen->pitch + x thing out of whack; it draws off the top of the screen a bit.
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

  4. #4
    Supermassive black hole cboard_member's Avatar
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    Jesus, I just tried rand()(omly) plotting pixels and CPU usage peaks at 77%. Mad.

    EDIT: Actually maybe that's normal. But it's still quite sticky.
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

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    You could just switch to directx and dump SDL thats what I did and I've never looked back.

  6. #6
    Supermassive black hole cboard_member's Avatar
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    Yeah that's what I want to do too. Meh. Stuff SDL.
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

  7. #7
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    BTW I just thought about it, aren't you suposed to always use main() with SDL? Or maybe it's SDL_Main or something? bah who cares?

  8. #8
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    Isn't SDL Software-rendered? That's probably why if it is.
    To code is divine

  9. #9
    Supermassive black hole cboard_member's Avatar
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    Quote Originally Posted by Quantum1024
    BTW I just thought about it, aren't you suposed to always use main() with SDL? Or maybe it's SDL_Main or something? bah who cares?
    Actually I just found the .lib "SDLmain.lib". How do I use this SDL main you speak of?

    EDIT: Nevermind. I've just linked it in and it runs nice now.
    Last edited by cboard_member; 04-09-2006 at 01:46 PM.
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

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