From: Konstanty <M DOT Bialkowski AT mailbox DOT uq DOT edu DOT au>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Allegro: Background
Date: Thu, 26 Feb 1998 17:14:29 +1000
Organization: University of Queensland
Lines: 194
Message-ID: <34F51654.F1A7B81E@mailbox.uq.edu.au>
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Reply-To: M DOT Bialkowski AT mailbox DOT uq DOT edu DOT au
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To: djgpp AT delorie DOT com
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C.Gugler wrote:

> I'm having trouble blitting a background to a simple Pong Game I'm
> making with DJGPP and Allegro. Before I put the code in to put a
> background bmp file in, it ran fine, at just the right speed.  After It
> started going slower and the Ball moves 'choppy'.  Is there anyway I can
> only have the bitmap drawn once without it have to redraw the whole
> thing every frame?  Right Now i'm using double buffering, I was thinking
> of trying Dirty Rectangles if that would go quicker.  Anyways, here's
> the code, If you have any suggestions, I'd be greatful..   Thanks in
> Advance..  Oh yeah, also if you have any info on how I could make it run
> as slow/fast on all machines(A pentium 300 won't go too much(or any)
> faster than a 486, or low-end pentium.)
>
> This is just the bottom portion of the C source file..

One thing you could do is have a background preset just before the main loop. Then copy the bitmap to another temp

bitmap (double buffering) on which everything is drawn.

>
>
> void pong_game(void)
> {
>    /* Set the first random direction for the ball */
>    direction=random_direction();
>  delay(200);

BITMAP *background=create_bitmap(640,480);
clear_to_color(background, 83);
blit(backdrop,background,0,0,10,30,620,455);
// you can add the some next on this background

// might need a change in background
int redraw=0;

>
>
>     /*Play the game while the ESC key is not pressed*/
>    while(!key[KEY_ESC])
>    {
>
> /* Used to change music... */
>  if(changem>9)
>   changem=0;
>    if(changem>0)
>   changem++;
>
> /* put background in, Too slow! */

blit(background,buffer,0,0,0,0,640,480);
if (redraw!=0){
clear_to_color(background, 83);
blit(backdrop,background,0,0,10,30,620,455);
// and other redrawing
redraw=0;
}

>       move_ball();
>       key_respond(); // respond to input and display paddle's
>
> /* Score's and Misc Info around the play area */
>     textout(buffer,pong_datafile[pfont].dat,"Player 1 Score:",150,0,21);
>
> textout(buffer,pong_datafile[pfont].dat,itoa(score_p1,NULL,10),text_length(pong_datafile[pfont].dat,"Player
> 1 Score:")+150,0,21);
>       textout(buffer,pong_datafile[pfont].dat,"Player 2
> Score:",350,0,21);
>
> textout(buffer,pong_datafile[pfont].dat,itoa(score_p2,NULL,10),text_length(pong_datafile[pfont].dat,"Player
> 2 Score:")+350,0,21);
>
>       textout(buffer,pong_datafile[pfont].dat,"A/Z",0,0,14);
>

// some of this text could be put into the background image

> textout(buffer,pong_datafile[pfont].dat,"Current Music
> Selection:",230,20,14);
>
> textout(buffer,pong_datafile[pfont].dat,itoa(cpong_midi,NULL,10),text_length(pong_datafile[pfont].dat,"Current
> Music Selection:")+230,20,14);
>
> textout(buffer,pong_datafile[pfont].dat,"Up/Down",618-text_length(pong_datafile[pfont].dat,"Up/Down"),0,14);
>
> textout(buffer,pong_datafile[pfont].dat,"Press 'M' to change
> Music",210,426,14);
>
> textout(buffer,pong_datafile[pfont].dat,"Press 'Esc' to
> Exit",210,4380,14);
>
> textout(buffer,pong_datafile[pfont].dat,"Special Thanks to, DJ
> Delorie(DJGPP), Shawn Hargreaves(Allegro), ",0,455,14);
>
> textout(buffer,pong_datafile[pfont].dat,"and anyone else who helped with
> Allegro or DJGPP.",0,465,14);
>
>       /* Draw a line to set the boundries */
>       line(buffer,0,30,640,30,252);
>       line(buffer,0,425,640,425,252);
>
>  /* Put the buffer screen on the screen */
>   vsync();
>       blit(buffer,screen,0,0,0,0,640,480);
>
>       /*Clear the buffer*/
>       clear_to_color(buffer, 83);
>    }
>    return;
> }
>
> int main(void)
> {
>  allegro_init();
>  install_timer();
>  install_keyboard();
>  initialise_joystick();
>  install_mouse();
>
>  if((pong_datafile=load_datafile("Cpong.dat"))==NULL)
>  {
>          /*Shutdown Allegro*/
>          allegro_exit();
>          /*Print error message*/
>          printf("Error loading \"Cpong.dat\"\n%s\n\n", allegro_error);
>          exit(1);
>  }
>
>  printf("Setting up the Sound...\n");
>
>  if(install_sound(DIGI_AUTODETECT,MIDI_AUTODETECT,NULL) != 0)
>  {
>          allegro_exit();
>          /*Print error message*/
>          printf("Error setting up Sound System\n%s\n\n", allegro_error);
>
>          exit(1);
>
>  }
>
>  printf("Setting up graphics mode 640x480...\n");
>
>  if (set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0) != 0)
>  {
>          allegro_exit();
>          /* Print error message */
>          printf("Error setting graphics mode 640 x 480\n%s\n\n",
> allegro_error);
>          exit(1);
>  }
>
>  /* Set the pallete for the bitmap */
>  set_pallete(pong_datafile[pal2].dat);
>
> backdrop=create_bitmap(620,455);
> blit(pong_datafile[titleb].dat, backdrop, 0, 0, 0, 0, 620, 455);
>
>  buffer=create_bitmap(640,480);
>  clear_to_color(buffer, 83);
>
>  /*Set the Ball position*/
>  ball_x=SCREEN_W/2;
>  ball_y=35;
>
> play_midi(pong_datafile[xcircus].dat, TRUE);
>
> while(!keypressed())
>   {
>   draw_rle_sprite(buffer,pong_datafile[title].dat,0,0);
>   textout(buffer,pong_datafile[pfont].dat,"Welcome...",3,468,5);
>   blit(buffer,screen,0,0,0,0,640,480);
>   }
>    /* Set the Pallete for the Sprites */
>   set_pallete(pong_datafile[pal].dat);
> /*Play the Game*/
>  clear_to_color(buffer, 83);
>  pong_game();
>
> stop_midi();
>  allegro_exit();
>
>  if(score_p1>score_p2)
>             printf("Player 1 wins! \n");
>  if(score_p2>score_p1)
>             printf("Player 2 wins! \n");
>  if(score_p1==score_p2)
>    printf("Player 1 and Player 2 Tied! \n");
>  return;
> }