test/testalpha.c
author Sam Lantinga <slouken@libsdl.org>
Mon, 21 Sep 2009 07:32:26 +0000
branchSDL-1.2
changeset 4209 62e86ab81e3c
parent 3868 b2f59aadec0d
child 5943 b442dbd2b6be
permissions -rw-r--r--
Fixed bug #570

SDL_SemWaitTimeout in src/thread/generic/SDL_syssem.c line 179 (SVN trunk):

--sem->count;

should be

if (retval == 0) {
--sem->count;
}

Without this, sem->count will underflow on timeout effectively breaking the
semaphore. It appears that the implementation has been wrong since the initial
revision.
     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 }