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
