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      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 #ifdef _WIN32_WCE
    509 					// there is no ESC key at all
    510 					done = 1;
    511 #else
    512 					if ( event.key.keysym.sym == SDLK_ESCAPE ) {
    513 						done = 1;
    514 					} else if (event.key.keysym.sym == SDLK_t) {
    515 						videoflags ^= SDL_FULLSCREEN;
    516 						screen = SDL_SetVideoMode(w, h, video_bpp, videoflags);
    517 						if ( screen == NULL ) {
    518 							fprintf(stderr, "Couldn't toggle video mode: %s\n",
    519 									SDL_GetError());
    520 							quit(2);
    521 						}
    522 						FillBackground(screen);
    523 					}
    524 #endif
    525 
    526 					break;
    527 				case SDL_QUIT:
    528 					done = 1;
    529 					break;
    530 				default:
    531 					break;
    532 			}
    533 		}
    534 	}
    535 	SDL_FreeSurface(light);
    536 	SDL_FreeSurface(sprite);
    537 	SDL_FreeSurface(backing);
    538 
    539 	/* Print out some timing information */
    540 	if ( flashes > 0 ) {
    541 		printf("%d alpha blits, ~%4.4f ms per blit\n",
    542 			flashes, (float)flashtime/flashes);
    543 	}
    544 
    545 	SDL_Quit();
    546 	return(0);
    547 }
    548