Thread: SDL_FillRect problem

I think there is something wrong but I can't figure out what.

I have an function that calls SDL_FillRect to fill the main screen with one colour but if I do that, the program just crashes and the log file is empty even though it was supposed to be written prior to the call!.

If I don't, the window is created normally and the log file is written.

Code:

int main(int argc, char* argv[]) {
  SDL_Surface* screen;    /* The screen that we draw on */
  SDL_Event event;        /* Events that we handle in our game loop */
  int done = 0;           /* The control for the game loop */
  
  logSetup();
  if(SDL_Init(SDL_INIT_EVERYTHING) == -1) {
    logWrite("Failed to initialise SDL: %s", SDL_GetError());
    SAFE_EXIT(-1);
  }
  initVideo(screen, 640, 480);
  
  SDL_WM_SetCaption(title, NULL);
  fillSurface(screen, FILL_WHITE); <- problem here
  
  while(!done) {
    while(SDL_PollEvent(&event)) {
      switch(event.type) {
        case SDL_QUIT: {
          logWrite("Application exit.");
          done = 1;
        }
      }
    }
  }
  SDL_Quit();
  logClose();
  return 0;
}

Code:

#ifndef SYSTEM_H
#define SYSTEM_H

...

/*
  This function sets the optimal video mode that the graphics adapter can
  handle. The parameter w and h indicates the video mode width and height
  that you want, if it isn't avaliable then the function would use what is
  avaliable. The function will automatically get the pixel format of the
  hardware.
*/
void initVideo(SDL_Surface* src, int w, int h);

...

/*
  These macros defines common RGB values to be passes to SDL_MapRGB.
*/
#define FILL_BLACK 0x00, 0x00, 0x00
#define FILL_WHITE 0xff, 0xff, 0xff
#define FILL_RED   0xff, 0x00, 0x00
#define FILL_GREEN 0x00, 0xff, 0x00
#define FILL_BLUE  0x00, 0x00, 0xff

void fillSurface(SDL_Surface* src, Uint8 R, Uint8 G, Uint8 B);

#endif

Code:

#include "system.h"

void initVideo(SDL_Surface* src, int w, int h) {
  const SDL_VideoInfo* info = SDL_GetVideoInfo();
  SDL_Rect** modes;
  Uint32 flags = 0, init = 0;
  Sint32 i;
  char driver[255];
  init = SDL_WasInit(SDL_INIT_VIDEO);
  if(init & SDL_INIT_VIDEO) {
    SDL_VideoDriverName(driver, 255);
    logWrite("Video initialised.");
    logWrite("Video driver name: %s", driver);
    if(info->hw_available) {  /* Check if video RAM is avaliable */
      flags |= SDL_HWSURFACE; /* If yes, use video RAM */
      flags |= SDL_DOUBLEBUF; /* Only hardware could use this */
      flags |= SDL_HWPALETTE; /* Exclusive palette access */
      logWrite("Hardware surface avaliable, using video memory.");
    } else {
      flags |= SDL_SWSURFACE; /* Use system RAM */
    }
    modes = SDL_ListModes(info->vfmt, flags); /* Get list of avaliable resolutions */
    if(modes == (SDL_Rect**)0) {              /* No resolutions avaliable */
      logWrite("No resolutions avaliable.");
      SAFE_EXIT(-1);
    } else if(modes == (SDL_Rect**)-1) {      /* All resolutions avaliable */
      logWrite("All resolution avaliable.");
      /* So we use the desired resolution */
      src = SDL_SetVideoMode(w, h, info->vfmt->BitsPerPixel, flags);
    } else {                      /* Only if we are limited to some resolutions */
      for(i = 0; modes[i]; ++i) { /* Find out how many avaliable resolutions */
      }
      i /= 2; /* Choose the optimal medium , not too large, not too small mode */
      src = SDL_SetVideoMode(modes[i]->w, modes[i]->h, info->vfmt->BitsPerPixel, flags);
    }
    if(src == NULL) {
      logWrite("Unable to set video mode: %s", SDL_GetError());
      SAFE_EXIT(-1);
    } else {
      logWrite("Video mode: %d x %d, %d bits per pixel", src->w, src->h, src->format->BitsPerPixel);
    }
    return;
  }
  SAFE_EXIT(-1);
}

...

void unlock(SDL_Surface* src) {
  if(SDL_MUSTLOCK(src)) {
    SDL_UnlockSurface(src);
  }
  return;
}

void fillSurface(SDL_Surface* src, Uint8 R, Uint8 G, Uint8 B) {
  Uint32 color = SDL_MapRGB(src->format, R, G, B);
  if(SDL_FillRect(src, NULL, color) == -1) {
    logWrite("Unable to fill surface: %s", SDL_GetError());
    SAFE_EXIT(-1);
  }
  SDL_UpdateRect(src, 0, 0, 0, 0);
  return;
}

I've cut the useless working bits out, I am concerned about the initialising function, because it does it's job when fillSurface() is not called but if it is, it doesn't seen to do anything because the log file isn't written! I'm sure there must be something wrong but I've already checked and tested so many times.

Please help! I can't continue writing the program if I can't sort this out.

Ah, fixed, thanks.

BTW, why couldn't it make it point to something else? SDL_SetVideoMode returns a pointer, why can't I assign that to my pointer?

Ok, thanks for the explaination. I've figured it out through the provided example. Pass argument by reference!

So if I had passed a SDL_Surface** src, in the code I should assign *src = SDL_SetVideoMode(...) to make them pointing at the same SDL_Surface.