[SDL] Help needed: flickering / not responding when blitting multiple times

[Martin Gorostegui]

Hi, 
   
  I'm starting with SDL (version 1.2.11 under win XP SP2). I have implemented a simple program to paint the screen of a different color 100 times. To do this I use an additional surface which pixels are modified in a loop and then I blit both surfaces. This is repeated 100 times, but I have the following problem:
   
  If I let everything run without limiting the speed I get a lot of flickering (actually using software surfaces, but tried with hardware, double buffer, etc and could not get rid of the flickering ever) so I decided to introduce a delay for each frame. Unfortunately when I do so my program keeps running ok but after a couple of frames the corresponding window appears as Not Responding and it gets blank.
   
  The code is as simple as the following:
   
  #include "SDL/SDL.h"
#include <string>
#include <iostream>
#include <windows.h>
  using namespace std;
  const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;
const int SCREEN_BPP = 32;
const int SCREEN_TOTAL_PIXELS = SCREEN_WIDTH * SCREEN_HEIGHT;
  SDL_Surface *screen = NULL;
SDL_Surface *image = NULL;
Uint32 imagePixels[SCREEN_TOTAL_PIXELS];
  void apply_surface( int x, int y, SDL_Surface* source, SDL_Surface* destination ) {
    //Make a temporary rectangle to hold the offsets
    SDL_Rect offset;
    //Give the offsets to the rectangle
    offset.x = x;
    offset.y = y; 
    //Blit the surface
    SDL_BlitSurface( source, NULL, destination, &offset );
}
  int main( int argc, char* args[] ) {
 //Initialize all SDL subsystems
    if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 ) {
        return 1;    
    }
 //Set up the screen
    screen = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE);
 int framesShown = 0;
 int i;
 SDL_PixelFormat *screenPixelFormat = screen->format;
 // create the image surface from the pixels setted above
 image = SDL_CreateRGBSurfaceFrom(imagePixels, SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, screen->pitch, 0, 0, 0, 0);
 while (framesShown<100) { 
  cout << "Frame: " << framesShown << "\n";
  for(i = 0; i < SCREEN_TOTAL_PIXELS; i++) {
   imagePixels[i] = 1000000 + (100 * framesShown);
  }
  // apply the image to the screen
  apply_surface( 0, 0, image, screen );
  //Update the screen
  if( SDL_Flip( screen ) == -1 ) {
   return 1;    
  }
  framesShown++;
  int j = 0;
  //Sleep(100);
 }
 SDL_FreeSurface( image );
 //Quit SDL
    SDL_Quit();
    return 0;
}
   
   
  Any ideas please?
   
  Thanks in advanced,
   
  Martin G

       
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