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. */
quit(int rc)16 static void quit(int rc)
17 {
18 SDL_Quit();
19 exit(rc);
20 }
21
22 /* Fill the screen with a gradient */
FillBackground(SDL_Surface * screen)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 */
CreateLight(int radius)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
FlashLight(SDL_Surface * screen,SDL_Surface * light,int x,int y)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
LoadSprite(SDL_Surface * screen,const char * file)181 int LoadSprite(SDL_Surface *screen, const 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
AttractSprite(Uint16 x,Uint16 y)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
MoveSprite(SDL_Surface * screen,SDL_Surface * light)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
WarpSprite(SDL_Surface * screen,int x,int y)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
main(int argc,char * argv[])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