/*
 *    Example program for the Allegro library, by Shawn Hargreaves.
 *
 *    This program demonstrates how to write directly to video memory.
 *    It implements a simple fire effect, first by calling getpixel() and
 *    putpixel(), then by accessing video memory directly a byte at a
 *    time, and finally using block memory copy operations.
 */


#include "allegro.h"



/* The fire is formed from several 'hotspots' which are moved randomly
 * across the bottom of the screen.
 */
#define FIRE_HOTSPOTS   48

int hotspot[FIRE_HOTSPOTS]; 

unsigned char *temp;



/* This function updates the bottom line of the screen with a pattern
 * of varying intensities which are then moved upwards and faded out
 * by the code in main().
 */
void draw_bottom_line_of_fire(void)
{
   int c, c2;

   /* zero the buffer */
   for (c=0; c<SCREEN_W; c++)
      temp[c] = 0;

   for (c=0; c<FIRE_HOTSPOTS; c++) { 
      /* display the hotspots */
      for (c2=hotspot[c]-20; c2<hotspot[c]+20; c2++)
	 if ((c2 >= 0) && (c2 < SCREEN_W))
	    temp[c2] = MIN(temp[c2] + 20-ABS(hotspot[c]-c2), 192);

      /* move the hotspots */
      hotspot[c] += (rand() & 7) - 3; 
      if (hotspot[c] < 0)
	 hotspot[c] += SCREEN_W;
      else
	 if (hotspot[c] >= SCREEN_W)
	    hotspot[c] -= SCREEN_W;
   }

   /* display the buffer */
   for (c=0; c<SCREEN_W; c++)
      putpixel(screen, c, SCREEN_H-1, temp[c]);
}



int main(void)
{
   PALETTE palette;
   unsigned long address;
   int x, y, c;

   allegro_init();
   install_keyboard(); 
   if (set_gfx_mode(GFX_AUTODETECT, 320, 200, 0, 0) != 0) {
      if (set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0) != 0) {
	 allegro_message("Error setting graphics mode\n%s\n", allegro_error);
	 return 1;
      }
   }

   temp = (unsigned char *)malloc(sizeof(unsigned char) * SCREEN_W);

   if (!temp) {
      set_gfx_mode(GFX_TEXT, 0, 0, 0, 0);
      allegro_message("Not enough memory? This is a joke right!?!\n");
      return 0;
   }

   for (c=0; c<FIRE_HOTSPOTS; c++)
      hotspot[c] = rand() % SCREEN_W;

   /* fill our palette with a gradually altering sequence of colors */
   for (c=0; c<64; c++) {
      palette[c].r = c;
      palette[c].g = 0;
      palette[c].b = 0;
   }
   for (c=64; c<128; c++) {
      palette[c].r = 63;
      palette[c].g = c-64;
      palette[c].b = 0;
   }
   for (c=128; c<192; c++) {
      palette[c].r = 63;
      palette[c].g = 63;
      palette[c].b = c-192;
   }
   for (c=192; c<256; c++) {
      palette[c].r = 63;
      palette[c].g = 63;
      palette[c].b = 63;
   }

   set_palette(palette);

   textout(screen, font, "Using get/putpixel()", 0, 0, makecol(255,255,255));

   /* using getpixel() and putpixel() is slow :-) */
   while (!keypressed()) {
      acquire_screen();

      draw_bottom_line_of_fire();

      for (y=64; y<SCREEN_H-1; y++) {
	 /* read line */
	 for (x=0; x<SCREEN_W; x++) {
	    c = getpixel(screen, x, y+1);

	    if (c > 0)
	       c--;

	    putpixel(screen, x, y, c);
	 }
      }
      release_screen();
   }

   clear_keybuf();
   textout(screen, font, "Using direct memory writes", 0, 0, makecol(255,255,255));

   /* It is much faster if we access the screen memory directly. This
    * time we read an entire line of the screen into our own buffer,
    * modify it there, and then write the whole line back in one go.
    * That is to avoid having to keep switching back and forth between
    * different scanlines: if we only copied one pixel at a time, we
    * would have to call bmp_write_line() for every single pixel rather
    * than just twice per line.
    */
   while (!keypressed()) {
      acquire_screen();
      draw_bottom_line_of_fire();

      bmp_select(screen);

      for (y=64; y<SCREEN_H-1; y++) {
	 /* get an address for reading line y+1 */
	 address = bmp_read_line(screen, y+1);

	 /* read line with farptr functions */
	 for (x=0; x<SCREEN_W; x++)
	    temp[x] = bmp_read8(address+x);

	 /* adjust it */
	 for (x=0; x<SCREEN_W; x++)
	    if (temp[x] > 0)
	       temp[x]--;

	 /* get an address for writing line y */
	 address = bmp_write_line(screen, y);

	 /* write line with farptr functions */
	 for (x=0; x<SCREEN_W; x++)
	    bmp_write8(address+x, temp[x]);
      }

      bmp_unwrite_line(screen);
      release_screen();
   }

   clear_keybuf();
   textout(screen, font, "Using block data transfers", 0, 0, makecol(255,255,255));

   /* It is even faster if we transfer the data in 32 bit chunks, rather
    * than only one pixel at a time. This method may not work on really
    * unusual machine architectures, but should be ok on just about
    * anything that you are practically likely to come across.
    */
   while (!keypressed()) {
      acquire_screen();
      draw_bottom_line_of_fire();

      bmp_select(screen);

      for (y=64; y<SCREEN_H-1; y++) {
	 /* get an address for reading line y+1 */
	 address = bmp_read_line(screen, y+1);

	 /* read line in 32 bit chunks */
	 for (x=0; x<SCREEN_W; x += sizeof(unsigned long))
	    *((unsigned long *)&temp[x]) = bmp_read32(address+x);

	 /* adjust it */
	 for (x=0; x<SCREEN_W; x++)
	    if (temp[x] > 0)
	       temp[x]--;

	 /* get an address for writing line y */
	 address = bmp_write_line(screen, y);

	 /* write line in 32 bit chunks */
	 for (x=0; x<SCREEN_W; x += sizeof(unsigned long))
	    bmp_write32(address+x, *((unsigned long *)&temp[x]));
      }

      bmp_unwrite_line(screen);
      release_screen();
   }

   free(temp);

   return 0;
}

END_OF_MAIN();
