From: JAB <jab_joe AT my-deja DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Allegro screen writing.
Date: Thu, 16 Sep 1999 17:55:16 GMT
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 My program won't run. I don't know what's wrong but it's something to
do with me miss-using allegro. The problem is something
do with the putpixel() bit of code. I think it's to do with the
global "screen" thing.


 This is a cut of the relavent (ie screen/allegro) related code from my
void main.

void main(void)
{
  BITMAP *bmp = screen;
  if (allegro_init()!=0){printf("Allegro load up error\n");return;}
  [snip]

  /* Set up screen */
  set_color_depth(24);
  if (set_gfx_mode(GFX_AUTODETECT, VDU_X, VDU_Y, 0, 0) != 0)
  {
    printf("Error setting video mode\n");
    return;
  }

  [snip]
}

 Here is my routine to plot the ready done image (it's in the ToDiplay
array) in main memory to the on screen memory
 pixel by pixel.

void display(void)
{
  register unsigned int x,y,tempnum;
  for(y=0;y<=VDU_Y;y++)
  {
    for(x=0;x<=VDU_X;x++)
    {
      putpixel(screen, x, y, ToDisplay[tempnum]); /* This is the line
the debugger points me to */
      /* ToDisplay is a 1D array of the screen info to be put on screen
*/
      tempnum++;
    }
  }
}

 What is wrong with the putpixel line? Is there something I should have
done with "screen"?
 I know the way I'm doing things isn't the best for PC. Writing to
things to a main memory array then plotting directly
to the screen from that. But the program wasn't written for the PC, I
just need to get it running, no matter how crude,
 and in a short space of time. Maybe I'll come back to it latter and
change all the lines plotting to ToDisplay, but I've
not got time now.

 Thanks for any help.


--
Catch ya later

JAB


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