1 

     2 /* Simple program:  Fill a colormap with gray and stripe it down the screen,

     3 		    Then move an alpha valued sprite around the screen.

     4  */

     5 

     6 #include <stdio.h>

     7 #include <stdlib.h>

     8 #include <string.h>

     9 #include <math.h>

    10 

    11 #include "SDL.h"

    12 

    13 #define FRAME_TICKS	(1000/30)		/* 30 frames/second */

    14 

    15 /* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */

    16 static void quit(int rc)

    17 {

    18 	SDL_Quit();

    19 	exit(rc);

    20 }

    21 

    22 /* Fill the screen with a gradient */

    23 static void FillBackground(SDL_Surface *screen)

    24 {

    25 	Uint8 *buffer;

    26 	Uint16 *buffer16;

    27         Uint16 color;

    28         Uint8  gradient;

    29 	int    i, k;

    30 

    31 	/* Set the surface pixels and refresh! */

    32 	if ( SDL_LockSurface(screen) < 0 ) {

    33 		fprintf(stderr, "Couldn't lock the display surface: %s\n",

    34 							SDL_GetError());

    35 		quit(2);

    36 	}

    37 	buffer=(Uint8 *)screen->pixels;

    38 	if (screen->format->BytesPerPixel!=2) {

    39 		for ( i=0; i<screen->h; ++i ) {

    40 			memset(buffer,(i*255)/screen->h, screen->w*screen->format->BytesPerPixel);

    41 			buffer += screen->pitch;

    42 		}

    43 	}

    44         else

    45         {

    46 		for ( i=0; i<screen->h; ++i ) {

    47 			gradient=((i*255)/screen->h);

    48                         color = (Uint16)SDL_MapRGB(screen->format, gradient, gradient, gradient);

    49                         buffer16=(Uint16*)buffer;

    50                         for (k=0; k<screen->w; k++)

    51                         {

    52                             *(buffer16+k)=color;

    53                         }

    54 			buffer += screen->pitch;

    55 		}

    56         }

    57 

    58 	SDL_UnlockSurface(screen);

    59 	SDL_UpdateRect(screen, 0, 0, 0, 0);

    60 }

    61 

    62 /* Create a "light" -- a yellowish surface with variable alpha */

    63 SDL_Surface *CreateLight(int radius)

    64 {

    65 	Uint8  trans, alphamask;

    66 	int    range, addition;

    67 	int    xdist, ydist;

    68 	Uint16 x, y;

    69 	Uint16 skip;

    70 	Uint32 pixel;

    71 	SDL_Surface *light;

    72 

    73 #ifdef LIGHT_16BIT

    74 	Uint16 *buf;

    75 

    76 	/* Create a 16 (4/4/4/4) bpp square with a full 4-bit alpha channel */

    77 	/* Note: this isn't any faster than a 32 bit alpha surface */

    78 	alphamask = 0x0000000F;

    79 	light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 16,

    80 			0x0000F000, 0x00000F00, 0x000000F0, alphamask);

    81 #else

    82 	Uint32 *buf;

    83 

    84 	/* Create a 32 (8/8/8/8) bpp square with a full 8-bit alpha channel */

    85 	alphamask = 0x000000FF;

    86 	light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 32,

    87 			0xFF000000, 0x00FF0000, 0x0000FF00, alphamask);

    88 	if ( light == NULL ) {

    89 		fprintf(stderr, "Couldn't create light: %s\n", SDL_GetError());

    90 		return(NULL);

    91 	}

    92 #endif

    93 

    94 	/* Fill with a light yellow-orange color */

    95 	skip = light->pitch-(light->w*light->format->BytesPerPixel);

    96 #ifdef LIGHT_16BIT

    97 	buf = (Uint16 *)light->pixels;

    98 #else

    99 	buf = (Uint32 *)light->pixels;

   100 #endif

   101         /* Get a tranparent pixel value - we'll add alpha later */

   102 	pixel = SDL_MapRGBA(light->format, 0xFF, 0xDD, 0x88, 0);

   103 	for ( y=0; y<light->h; ++y ) {

   104 		for ( x=0; x<light->w; ++x ) {

   105 			*buf++ = pixel;

   106 		}

   107 		buf += skip;	/* Almost always 0, but just in case... */

   108 	}

   109 

   110 	/* Calculate alpha values for the surface. */

   111 #ifdef LIGHT_16BIT

   112 	buf = (Uint16 *)light->pixels;

   113 #else

   114 	buf = (Uint32 *)light->pixels;

   115 #endif

   116 	for ( y=0; y<light->h; ++y ) {

   117 		for ( x=0; x<light->w; ++x ) {

   118 			/* Slow distance formula (from center of light) */

   119 			xdist = x-(light->w/2);

   120 			ydist = y-(light->h/2);

   121 			range = (int)sqrt(xdist*xdist+ydist*ydist);

   122 

   123 			/* Scale distance to range of transparency (0-255) */

   124 			if ( range > radius ) {

   125 				trans = alphamask;

   126 			} else {

   127 				/* Increasing transparency with distance */

   128 				trans = (Uint8)((range*alphamask)/radius);

   129 

   130 				/* Lights are very transparent */

   131 				addition = (alphamask+1)/8;

   132 				if ( (int)trans+addition > alphamask ) {

   133 					trans = alphamask;

   134 				} else {

   135 					trans += addition;

   136 				}

   137 			}

   138 			/* We set the alpha component as the right N bits */

   139 			*buf++ |= (255-trans);

   140 		}

   141 		buf += skip;	/* Almost always 0, but just in case... */

   142 	}

   143 	/* Enable RLE acceleration of this alpha surface */

   144 	SDL_SetAlpha(light, SDL_SRCALPHA|SDL_RLEACCEL, 0);

   145 

   146 	/* We're done! */

   147 	return(light);

   148 }

   149 

   150 static Uint32 flashes = 0;

   151 static Uint32 flashtime = 0;

   152 

   153 void FlashLight(SDL_Surface *screen, SDL_Surface *light, int x, int y)

   154 {

   155 	SDL_Rect position;

   156 	Uint32   ticks1;

   157 	Uint32   ticks2;

   158 

   159 	/* Easy, center light */

   160 	position.x = x-(light->w/2);

   161 	position.y = y-(light->h/2);

   162 	position.w = light->w;

   163 	position.h = light->h;

   164 	ticks1 = SDL_GetTicks();

   165 	SDL_BlitSurface(light, NULL, screen, &position);

   166 	ticks2 = SDL_GetTicks();

   167 	SDL_UpdateRects(screen, 1, &position);

   168 	++flashes;

   169 

   170 	/* Update time spend doing alpha blitting */

   171 	flashtime += (ticks2-ticks1);

   172 }

   173 

   174 static int sprite_visible = 0;

   175 static SDL_Surface *sprite;

   176 static SDL_Surface *backing;

   177 static SDL_Rect    position;

   178 static int         x_vel, y_vel;

   179 static int	   alpha_vel;

   180 

   181 int LoadSprite(SDL_Surface *screen, char *file)

   182 {

   183 	SDL_Surface *converted;

   184 

   185 	/* Load the sprite image */

   186 	sprite = SDL_LoadBMP(file);

   187 	if ( sprite == NULL ) {

   188 		fprintf(stderr, "Couldn't load %s: %s", file, SDL_GetError());

   189 		return(-1);

   190 	}

   191 

   192 	/* Set transparent pixel as the pixel at (0,0) */

   193 	if ( sprite->format->palette ) {

   194 		SDL_SetColorKey(sprite, SDL_SRCCOLORKEY,

   195 						*(Uint8 *)sprite->pixels);

   196 	}

   197 

   198 	/* Convert sprite to video format */

   199 	converted = SDL_DisplayFormat(sprite);

   200 	SDL_FreeSurface(sprite);

   201 	if ( converted == NULL ) {

   202 		fprintf(stderr, "Couldn't convert background: %s\n",

   203 							SDL_GetError());

   204 		return(-1);

   205 	}

   206 	sprite = converted;

   207 

   208 	/* Create the background */

   209 	backing = SDL_CreateRGBSurface(SDL_SWSURFACE, sprite->w, sprite->h, 8,

   210 								0, 0, 0, 0);

   211 	if ( backing == NULL ) {

   212 		fprintf(stderr, "Couldn't create background: %s\n",

   213 							SDL_GetError());

   214 		SDL_FreeSurface(sprite);

   215 		return(-1);

   216 	}

   217 

   218 	/* Convert background to video format */

   219 	converted = SDL_DisplayFormat(backing);

   220 	SDL_FreeSurface(backing);

   221 	if ( converted == NULL ) {

   222 		fprintf(stderr, "Couldn't convert background: %s\n",

   223 							SDL_GetError());

   224 		SDL_FreeSurface(sprite);

   225 		return(-1);

   226 	}

   227 	backing = converted;

   228 

   229 	/* Set the initial position of the sprite */

   230 	position.x = (screen->w-sprite->w)/2;

   231 	position.y = (screen->h-sprite->h)/2;

   232 	position.w = sprite->w;

   233 	position.h = sprite->h;

   234 	x_vel = 0; y_vel = 0;

   235 	alpha_vel = 1;

   236 

   237 	/* We're ready to roll. :) */

   238 	return(0);

   239 }

   240 

   241 void AttractSprite(Uint16 x, Uint16 y)

   242 {

   243 	x_vel = ((int)x-position.x)/10;

   244 	y_vel = ((int)y-position.y)/10;

   245 }

   246 

   247 void MoveSprite(SDL_Surface *screen, SDL_Surface *light)

   248 {

   249 	SDL_Rect updates[2];

   250 	int alpha;

   251 

   252 	/* Erase the sprite if it was visible */

   253 	if ( sprite_visible ) {

   254 		updates[0] = position;

   255 		SDL_BlitSurface(backing, NULL, screen, &updates[0]);

   256 	} else {

   257 		updates[0].x = 0; updates[0].y = 0;

   258 		updates[0].w = 0; updates[0].h = 0;

   259 		sprite_visible = 1;

   260 	}

   261 

   262 	/* Since the sprite is off the screen, we can do other drawing

   263 	   without being overwritten by the saved area behind the sprite.

   264 	 */

   265 	if ( light != NULL ) {

   266 		int x, y;

   267 

   268 		SDL_GetMouseState(&x, &y);

   269 		FlashLight(screen, light, x, y);

   270 	}

   271 	   

   272 	/* Move the sprite, bounce at the wall */

   273 	position.x += x_vel;

   274 	if ( (position.x < 0) || (position.x >= screen->w) ) {

   275 		x_vel = -x_vel;

   276 		position.x += x_vel;

   277 	}

   278 	position.y += y_vel;

   279 	if ( (position.y < 0) || (position.y >= screen->h) ) {

   280 		y_vel = -y_vel;

   281 		position.y += y_vel;

   282 	}

   283 

   284 	/* Update transparency (fade in and out) */

   285 	alpha = sprite->format->alpha;

   286 	if ( (alpha+alpha_vel) < 0 ) {

   287 		alpha_vel = -alpha_vel;

   288 	} else

   289 	if ( (alpha+alpha_vel) > 255 ) {

   290 		alpha_vel = -alpha_vel;

   291 	}

   292 	SDL_SetAlpha(sprite, SDL_SRCALPHA, (Uint8)(alpha+alpha_vel));

   293 

   294 	/* Save the area behind the sprite */

   295 	updates[1] = position;

   296 	SDL_BlitSurface(screen, &updates[1], backing, NULL);

   297 	

   298 	/* Blit the sprite onto the screen */

   299 	updates[1] = position;

   300 	SDL_BlitSurface(sprite, NULL, screen, &updates[1]);

   301 

   302 	/* Make it so! */

   303 	SDL_UpdateRects(screen, 2, updates);

   304 }

   305 

   306 void WarpSprite(SDL_Surface *screen, int x, int y)

   307 {

   308 	SDL_Rect updates[2];

   309 

   310 	/* Erase, move, Draw, update */

   311 	updates[0] = position;

   312 	SDL_BlitSurface(backing, NULL, screen, &updates[0]);

   313 	position.x = x-sprite->w/2;	/* Center about X */

   314 	position.y = y-sprite->h/2;	/* Center about Y */

   315 	updates[1] = position;

   316 	SDL_BlitSurface(screen, &updates[1], backing, NULL);

   317 	updates[1] = position;

   318 	SDL_BlitSurface(sprite, NULL, screen, &updates[1]);

   319 	SDL_UpdateRects(screen, 2, updates);

   320 }

   321 

   322 int main(int argc, char *argv[])

   323 {

   324 	const SDL_VideoInfo *info;

   325 	SDL_Surface *screen;

   326 	int    w, h;

   327 	Uint8  video_bpp;

   328 	Uint32 videoflags;

   329 	int    i, done;

   330 	SDL_Event event;

   331 	SDL_Surface *light;

   332 	int mouse_pressed;

   333 	Uint32 ticks, lastticks;

   334 

   335 

   336 	/* Initialize SDL */

   337 	if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {

   338 		fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());

   339 		return(1);

   340 	}

   341 

   342 	/* Alpha blending doesn't work well at 8-bit color */

   343 #ifdef _WIN32_WCE

   344 	/* Pocket PC */

   345 	w = 240;

   346 	h = 320;

   347 #else

   348 	w = 640;

   349 	h = 480;

   350 #endif

   351 	info = SDL_GetVideoInfo();

   352 	if ( info->vfmt->BitsPerPixel > 8 ) {

   353 		video_bpp = info->vfmt->BitsPerPixel;

   354 	} else {

   355 		video_bpp = 16;

   356                 fprintf(stderr, "forced 16 bpp mode\n");

   357 	}

   358 	videoflags = SDL_SWSURFACE;

   359 	for ( i = 1; argv[i]; ++i ) {

   360 		if ( strcmp(argv[i], "-bpp") == 0 ) {

   361 			video_bpp = atoi(argv[++i]);

   362                         if (video_bpp<=8) {

   363                             video_bpp=16;

   364                             fprintf(stderr, "forced 16 bpp mode\n");

   365                         }

   366 		} else

   367 		if ( strcmp(argv[i], "-hw") == 0 ) {

   368 			videoflags |= SDL_HWSURFACE;

   369 		} else

   370 		if ( strcmp(argv[i], "-warp") == 0 ) {

   371 			videoflags |= SDL_HWPALETTE;

   372 		} else

   373 		if ( strcmp(argv[i], "-width") == 0 && argv[i+1] ) {

   374 			w = atoi(argv[++i]);

   375 		} else

   376 		if ( strcmp(argv[i], "-height") == 0 && argv[i+1] ) {

   377 			h = atoi(argv[++i]);

   378 		} else

   379 		if ( strcmp(argv[i], "-resize") == 0 ) {

   380 			videoflags |= SDL_RESIZABLE;

   381 		} else

   382 		if ( strcmp(argv[i], "-noframe") == 0 ) {

   383 			videoflags |= SDL_NOFRAME;

   384 		} else

   385 		if ( strcmp(argv[i], "-fullscreen") == 0 ) {

   386 			videoflags |= SDL_FULLSCREEN;

   387 		} else {

   388 			fprintf(stderr, 

   389 			"Usage: %s [-width N] [-height N] [-bpp N] [-warp] [-hw] [-fullscreen]\n",

   390 								argv[0]);

   391 			quit(1);

   392 		}

   393 	}

   394 

   395 	/* Set video mode */

   396 	if ( (screen=SDL_SetVideoMode(w,h,video_bpp,videoflags)) == NULL ) {

   397 		fprintf(stderr, "Couldn't set %dx%dx%d video mode: %s\n",

   398 						w, h, video_bpp, SDL_GetError());

   399 		quit(2);

   400 	}

   401 	FillBackground(screen);

   402 

   403 	/* Create the light */

   404 	light = CreateLight(82);

   405 	if ( light == NULL ) {

   406 		quit(1);

   407 	}

   408 

   409 	/* Load the sprite */

   410 	if ( LoadSprite(screen, "icon.bmp") < 0 ) {

   411 		SDL_FreeSurface(light);

   412 		quit(1);

   413 	}

   414 

   415 	/* Print out information about our surfaces */

   416 	printf("Screen is at %d bits per pixel\n",screen->format->BitsPerPixel);

   417 	if ( (screen->flags & SDL_HWSURFACE) == SDL_HWSURFACE ) {

   418 		printf("Screen is in video memory\n");

   419 	} else {

   420 		printf("Screen is in system memory\n");

   421 	}

   422 	if ( (screen->flags & SDL_DOUBLEBUF) == SDL_DOUBLEBUF ) {

   423 		printf("Screen has double-buffering enabled\n");

   424 	}

   425 	if ( (sprite->flags & SDL_HWSURFACE) == SDL_HWSURFACE ) {

   426 		printf("Sprite is in video memory\n");

   427 	} else {

   428 		printf("Sprite is in system memory\n");

   429 	}

   430 

   431 	/* Run a sample blit to trigger blit acceleration */

   432 	MoveSprite(screen, NULL);

   433 	if ( (sprite->flags & SDL_HWACCEL) == SDL_HWACCEL ) {

   434 		printf("Sprite blit uses hardware alpha acceleration\n");

   435 	} else {

   436 		printf("Sprite blit dosn't uses hardware alpha acceleration\n");

   437 	}

   438 

   439 	/* Set a clipping rectangle to clip the outside edge of the screen */

   440 	{ SDL_Rect clip;

   441 		clip.x = 32;

   442 		clip.y = 32;

   443 		clip.w = screen->w-(2*32);

   444 		clip.h = screen->h-(2*32);

   445 		SDL_SetClipRect(screen, &clip);

   446 	}

   447 

   448 	/* Wait for a keystroke */

   449 	lastticks = SDL_GetTicks();

   450 	done = 0;

   451 	mouse_pressed = 0;

   452 	while ( !done ) {

   453 		/* Update the frame -- move the sprite */

   454 		if ( mouse_pressed ) {

   455 			MoveSprite(screen, light);

   456 			mouse_pressed = 0;

   457 		} else {

   458 			MoveSprite(screen, NULL);

   459 		}

   460 

   461 		/* Slow down the loop to 30 frames/second */

   462 		ticks = SDL_GetTicks();

   463 		if ( (ticks-lastticks) < FRAME_TICKS ) {

   464 #ifdef CHECK_SLEEP_GRANULARITY

   465 fprintf(stderr, "Sleeping %d ticks\n", FRAME_TICKS-(ticks-lastticks));

   466 #endif

   467 			SDL_Delay(FRAME_TICKS-(ticks-lastticks));

   468 #ifdef CHECK_SLEEP_GRANULARITY

   469 fprintf(stderr, "Slept %d ticks\n", (SDL_GetTicks()-ticks));

   470 #endif

   471 		}

   472 		lastticks = ticks;

   473 

   474 		/* Check for events */

   475 		while ( SDL_PollEvent(&event) ) {

   476 			switch (event.type) {

   477 				case SDL_VIDEORESIZE:

   478 					screen = SDL_SetVideoMode(event.resize.w, event.resize.h, video_bpp, videoflags);

   479 					if ( screen ) {

   480 						FillBackground(screen);

   481 					}

   482 					break;

   483 				/* Attract sprite while mouse is held down */

   484 				case SDL_MOUSEMOTION:

   485 					if (event.motion.state != 0) {

   486 						AttractSprite(event.motion.x,

   487 								event.motion.y);

   488 						mouse_pressed = 1;

   489 					}

   490 					break;

   491 				case SDL_MOUSEBUTTONDOWN:

   492 					if ( event.button.button == 1 ) {

   493 						AttractSprite(event.button.x,

   494 						              event.button.y);

   495 						mouse_pressed = 1;

   496 					} else {

   497 						SDL_Rect area;

   498 

   499 						area.x = event.button.x-16;

   500 						area.y = event.button.y-16;

   501 						area.w = 32;

   502 						area.h = 32;

   503 						SDL_FillRect(screen, &area, 0);

   504 						SDL_UpdateRects(screen,1,&area);

   505 					}

   506 					break;

   507 				case SDL_KEYDOWN:

   508 #ifndef _WIN32_WCE

   509 					if ( event.key.keysym.sym == SDLK_ESCAPE ) {

   510 						done = 1;

   511 					}

   512 #else

   513 					// there is no ESC key at all

   514 					done = 1;

   515 #endif

   516 					break;

   517 				case SDL_QUIT:

   518 					done = 1;

   519 					break;

   520 				default:

   521 					break;

   522 			}

   523 		}

   524 	}

   525 	SDL_FreeSurface(light);

   526 	SDL_FreeSurface(sprite);

   527 	SDL_FreeSurface(backing);

   528 

   529 	/* Print out some timing information */

   530 	if ( flashes > 0 ) {

   531 		printf("%d alpha blits, ~%4.4f ms per blit\n", 

   532 			flashes, (float)flashtime/flashes);

   533 	}

   534 

   535 	SDL_Quit();

   536 	return(0);

   537 }