From: jromano AT slate DOT Mines DOT EDU (Jean-Luc Romano)
Newsgroups: comp.os.msdos.djgpp
Subject: fade_out()
Date: 24 Jan 1998 08:12:48 GMT
Organization: Colorado School of Mines
Lines: 113
Message-ID: <6ac7q0$j2c$1@herald.Mines.EDU>
NNTP-Posting-Host: slate.mines.edu
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Precedence: bulk


Dear All,

   When programming in C using DJGPP and the Allegro graphics 
library, the fade_out() routine only seems to work once.

   The second fade_out() routine will only work if the first
fade_out() routine has been commented out.

   Try compiling my code below if you have trouble understanding
what I mean (the last fade_out() is in the third line from the
bottom).

   Any suggestions?  Thanks in advance.

   Jean-Luc Romano



/*
 * "Moving the Moon"
 *  by Jean-Luc Romano  (jromano AT mines DOT edu) 
 *          http://www.mines.edu/students/j/jromano/
 *  My first attempt at game programming, so don't laugh.
 *  Use the arrow keys and/or the joystic to control the moon.
 *  ESC key quits.
 *  The last fade_out() doesn't seem to work.  Any ideas?
 *  Special thanks to:  DJ Delorie and Shawn Hargreaves
 */

#include <stdio.h>
#include <allegro.h>

#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
#define PIXELMOVE 5

/* Function prototype(s): */
void main_code(void);

int main(void)
{
   allegro_init();
   install_keyboard();
   if (initialise_joystick())
   {
      printf("Could not detect joystick.\n");
   }
/*
   if (install_sound(DIGI_AUTODETECT, MIDI_AUTODETECT, NULL))
   {
      printf("Install_sound failed to work.\n");
      exit(1);
   }
*/
   install_timer();

   main_code();

   clear_keybuf();
   allegro_exit();
   return 0;
}

void main_code(void)
{
   int i, j;  /* counter(s) -- nothing more */
   int radius;
   int colour;
   BITMAP* temp_bitmap = create_bitmap(SCREEN_WIDTH, SCREEN_HEIGHT);
   BITMAP* bgmap = create_bitmap(SCREEN_WIDTH, SCREEN_HEIGHT);

 /*
   MIDI *the_music = load_midi("CANYON.MID");
   play_midi(the_music, TRUE);
 */

   fade_out(3);    /* first use of fade_out() -- this works just fine */
   set_gfx_mode(GFX_AUTODETECT, SCREEN_WIDTH, SCREEN_HEIGHT, 0, 0);
   clear(screen);
   clear_to_color(temp_bitmap, 0);
   radius = 100;
   circlefill(temp_bitmap, SCREEN_WIDTH / 2, SCREEN_HEIGHT / 2, radius, 14);
   text_mode(-1);
   textout_centre(temp_bitmap, font, "Watch for werewolves!", SCREEN_WIDTH / 2, SCREEN_HEIGHT / 2, 9);
   i = j = colour = 0;

   while(!key[KEY_ESC])
   {
      poll_joystick();
      if (key[KEY_UP] || joy_up)
         j -= PIXELMOVE;
      if (key[KEY_DOWN] || joy_down)
         j += PIXELMOVE ;
      if (key[KEY_RIGHT] || joy_right)
         i += PIXELMOVE;
      if (key[KEY_LEFT] || joy_left)
         i -= PIXELMOVE;

      clear_to_color(bgmap, colour);
      blit(temp_bitmap, bgmap, SCREEN_WIDTH / 2 - radius, SCREEN_HEIGHT / 2 - radius, SCREEN_WIDTH / 2 - radius + i, SCREEN_HEIGHT / 2 - radius + j, radius * 2, radius * 2);
      blit(bgmap, screen, 0, 0, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
      vsync();
   }
 /*
   stop_midi(the_music);
   destroy_midi(the_music);
 */

   fade_out(3);  /* This fade_out doesn't seem to work.  Any ideas? */
   return;
}