--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/testalpha.c	Thu Apr 26 16:45:43 2001 +0000
@@ -0,0 +1,440 @@
+
+/* Simple program:  Fill a colormap with gray and stripe it down the screen,
+		    Then move an alpha valued sprite around the screen.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+
+#include "SDL.h"
+
+#define FRAME_TICKS	(1000/30)		/* 30 frames/second */
+
+/* Create a "light" -- a yellowish surface with variable alpha */
+SDL_Surface *CreateLight(SDL_Surface *screen, int radius)
+{
+	Uint8  trans, alphamask;
+	int    range, addition;
+	int    xdist, ydist;
+	Uint16 x, y;
+	Uint16 skip;
+	Uint32 pixel;
+	SDL_Surface *light;
+
+#ifdef LIGHT_16BIT
+	Uint16 *buf;
+
+	/* Create a 16 (4/4/4/4) bpp square with a full 4-bit alpha channel */
+	/* Note: this isn't any faster than a 32 bit alpha surface */
+	alphamask = 0x0000000F;
+	light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 16,
+			0x0000F000, 0x00000F00, 0x000000F0, alphamask);
+#else
+	Uint32 *buf;
+
+	/* Create a 32 (8/8/8/8) bpp square with a full 8-bit alpha channel */
+	alphamask = 0x000000FF;
+	light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 32,
+			0xFF000000, 0x00FF0000, 0x0000FF00, alphamask);
+	if ( light == NULL ) {
+		fprintf(stderr, "Couldn't create light: %s\n", SDL_GetError());
+		return(NULL);
+	}
+#endif
+
+	/* Fill with a light yellow-orange color */
+	skip = light->pitch-(light->w*light->format->BytesPerPixel);
+#ifdef LIGHT_16BIT
+	buf = (Uint16 *)light->pixels;
+#else
+	buf = (Uint32 *)light->pixels;
+#endif
+        /* Get a tranparent pixel value - we'll add alpha later */
+	pixel = SDL_MapRGBA(light->format, 0xFF, 0xDD, 0x88, 0);
+	for ( y=0; y<light->h; ++y ) {
+		for ( x=0; x<light->w; ++x ) {
+			*buf++ = pixel;
+		}
+		buf += skip;	/* Almost always 0, but just in case... */
+	}
+
+	/* Calculate alpha values for the surface. */
+#ifdef LIGHT_16BIT
+	buf = (Uint16 *)light->pixels;
+#else
+	buf = (Uint32 *)light->pixels;
+#endif
+	for ( y=0; y<light->h; ++y ) {
+		for ( x=0; x<light->w; ++x ) {
+			/* Slow distance formula (from center of light) */
+			xdist = x-(light->w/2);
+			ydist = y-(light->h/2);
+			range = (int)sqrt(xdist*xdist+ydist*ydist);
+
+			/* Scale distance to range of transparency (0-255) */
+			if ( range > radius ) {
+				trans = alphamask;
+			} else {
+				/* Increasing transparency with distance */
+				trans = (Uint8)((range*alphamask)/radius);
+
+				/* Lights are very transparent */
+				addition = (alphamask+1)/8;
+				if ( (int)trans+addition > alphamask ) {
+					trans = alphamask;
+				} else {
+					trans += addition;
+				}
+			}
+			/* We set the alpha component as the right N bits */
+			*buf++ |= (255-trans);
+		}
+		buf += skip;	/* Almost always 0, but just in case... */
+	}
+	/* Enable RLE acceleration of this alpha surface */
+	SDL_SetAlpha(light, SDL_SRCALPHA|SDL_RLEACCEL, 0);
+
+	/* We're done! */
+	return(light);
+}
+
+static Uint32 flashes = 0;
+static Uint32 flashtime = 0;
+
+void FlashLight(SDL_Surface *screen, SDL_Surface *light, int x, int y)
+{
+	SDL_Rect position;
+	Uint32   ticks1;
+	Uint32   ticks2;
+
+	/* Easy, center light */
+	position.x = x-(light->w/2);
+	position.y = y-(light->h/2);
+	position.w = light->w;
+	position.h = light->h;
+	ticks1 = SDL_GetTicks();
+	SDL_BlitSurface(light, NULL, screen, &position);
+	ticks2 = SDL_GetTicks();
+	SDL_UpdateRects(screen, 1, &position);
+	++flashes;
+
+	/* Update time spend doing alpha blitting */
+	flashtime += (ticks2-ticks1);
+}
+
+static int sprite_visible = 0;
+static SDL_Surface *sprite;
+static SDL_Surface *backing;
+static SDL_Rect    position;
+static int         x_vel, y_vel;
+static int	   alpha_vel;
+
+int LoadSprite(SDL_Surface *screen, char *file)
+{
+	SDL_Surface *converted;
+
+	/* Load the sprite image */
+	sprite = SDL_LoadBMP(file);
+	if ( sprite == NULL ) {
+		fprintf(stderr, "Couldn't load %s: %s", file, SDL_GetError());
+		return(-1);
+	}
+
+	/* Set transparent pixel as the pixel at (0,0) */
+	if ( sprite->format->palette ) {
+		SDL_SetColorKey(sprite, SDL_SRCCOLORKEY,
+						*(Uint8 *)sprite->pixels);
+	}
+
+	/* Convert sprite to video format */
+	converted = SDL_DisplayFormat(sprite);
+	SDL_FreeSurface(sprite);
+	if ( converted == NULL ) {
+		fprintf(stderr, "Couldn't convert background: %s\n",
+							SDL_GetError());
+		return(-1);
+	}
+	sprite = converted;
+
+	/* Create the background */
+	backing = SDL_CreateRGBSurface(SDL_SWSURFACE, sprite->w, sprite->h, 8,
+								0, 0, 0, 0);
+	if ( backing == NULL ) {
+		fprintf(stderr, "Couldn't create background: %s\n",
+							SDL_GetError());
+		SDL_FreeSurface(sprite);
+		return(-1);
+	}
+
+	/* Convert background to video format */
+	converted = SDL_DisplayFormat(backing);
+	SDL_FreeSurface(backing);
+	if ( converted == NULL ) {
+		fprintf(stderr, "Couldn't convert background: %s\n",
+							SDL_GetError());
+		SDL_FreeSurface(sprite);
+		return(-1);
+	}
+	backing = converted;
+
+	/* Set the initial position of the sprite */
+	position.x = (screen->w-sprite->w)/2;
+	position.y = (screen->h-sprite->h)/2;
+	position.w = sprite->w;
+	position.h = sprite->h;
+	x_vel = 0; y_vel = 0;
+	alpha_vel = 1;
+
+	/* We're ready to roll. :) */
+	return(0);
+}
+
+void AttractSprite(Uint16 x, Uint16 y)
+{
+	x_vel = ((int)x-position.x)/10;
+	y_vel = ((int)y-position.y)/10;
+}
+
+void MoveSprite(SDL_Surface *screen, SDL_Surface *light)
+{
+	SDL_Rect updates[2];
+	int alpha;
+
+	/* Erase the sprite if it was visible */
+	if ( sprite_visible ) {
+		updates[0] = position;
+		SDL_BlitSurface(backing, NULL, screen, &updates[0]);
+	} else {
+		updates[0].x = 0; updates[0].y = 0;
+		updates[0].w = 0; updates[0].h = 0;
+		sprite_visible = 1;
+	}
+
+	/* Since the sprite is off the screen, we can do other drawing
+	   without being overwritten by the saved area behind the sprite.
+	 */
+	if ( light != NULL ) {
+		int x, y;
+
+		SDL_GetMouseState(&x, &y);
+		FlashLight(screen, light, x, y);
+	}
+	   
+	/* Move the sprite, bounce at the wall */
+	position.x += x_vel;
+	if ( (position.x < 0) || (position.x >= screen->w) ) {
+		x_vel = -x_vel;
+		position.x += x_vel;
+	}
+	position.y += y_vel;
+	if ( (position.y < 0) || (position.y >= screen->h) ) {
+		y_vel = -y_vel;
+		position.y += y_vel;
+	}
+
+	/* Update transparency (fade in and out) */
+	alpha = sprite->format->alpha;
+	if ( (alpha+alpha_vel) < 0 ) {
+		alpha_vel = -alpha_vel;
+	} else
+	if ( (alpha+alpha_vel) > 255 ) {
+		alpha_vel = -alpha_vel;
+	}
+	SDL_SetAlpha(sprite, SDL_SRCALPHA, (Uint8)(alpha+alpha_vel));
+
+	/* Save the area behind the sprite */
+	updates[1] = position;
+	SDL_BlitSurface(screen, &updates[1], backing, NULL);
+	
+	/* Blit the sprite onto the screen */
+	updates[1] = position;
+	SDL_BlitSurface(sprite, NULL, screen, &updates[1]);
+
+	/* Make it so! */
+	SDL_UpdateRects(screen, 2, updates);
+}
+
+void WarpSprite(SDL_Surface *screen, int x, int y)
+{
+	SDL_Rect updates[2];
+
+	/* Erase, move, Draw, update */
+	updates[0] = position;
+	SDL_BlitSurface(backing, NULL, screen, &updates[0]);
+	position.x = x-sprite->w/2;	/* Center about X */
+	position.y = y-sprite->h/2;	/* Center about Y */
+	updates[1] = position;
+	SDL_BlitSurface(screen, &updates[1], backing, NULL);
+	updates[1] = position;
+	SDL_BlitSurface(sprite, NULL, screen, &updates[1]);
+	SDL_UpdateRects(screen, 2, updates);
+}
+
+int main(int argc, char *argv[])
+{
+	const SDL_VideoInfo *info;
+	SDL_Surface *screen;
+	Uint8  video_bpp;
+	Uint32 videoflags;
+	Uint8 *buffer;
+	int    i, done;
+	SDL_Event event;
+	SDL_Surface *light;
+	int mouse_pressed;
+	Uint32 ticks, lastticks;
+
+	/* Initialize SDL */
+	if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
+		fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());
+		exit(1);
+	}
+	atexit(SDL_Quit);
+
+	/* Alpha blending doesn't work well at 8-bit color */
+	info = SDL_GetVideoInfo();
+	if ( info->vfmt->BitsPerPixel > 8 ) {
+		video_bpp = info->vfmt->BitsPerPixel;
+	} else {
+		video_bpp = 16;
+	}
+	videoflags = SDL_SWSURFACE;
+	while ( argc > 1 ) {
+		--argc;
+		if ( strcmp(argv[argc-1], "-bpp") == 0 ) {
+			video_bpp = atoi(argv[argc]);
+			--argc;
+		} else
+		if ( strcmp(argv[argc], "-hw") == 0 ) {
+			videoflags |= SDL_HWSURFACE;
+		} else
+		if ( strcmp(argv[argc], "-warp") == 0 ) {
+			videoflags |= SDL_HWPALETTE;
+		} else
+		if ( strcmp(argv[argc], "-fullscreen") == 0 ) {
+			videoflags |= SDL_FULLSCREEN;
+		} else {
+			fprintf(stderr, 
+			"Usage: %s [-bpp N] [-warp] [-hw] [-fullscreen]\n",
+								argv[0]);
+			exit(1);
+		}
+	}
+
+	/* Set 640x480 video mode */
+	if ( (screen=SDL_SetVideoMode(640,480,video_bpp,videoflags)) == NULL ) {
+		fprintf(stderr, "Couldn't set 640x480x%d video mode: %s\n",
+						video_bpp, SDL_GetError());
+		exit(2);
+	}
+
+	/* Set the surface pixels and refresh! */
+	if ( SDL_LockSurface(screen) < 0 ) {
+		fprintf(stderr, "Couldn't lock the display surface: %s\n",
+							SDL_GetError());
+		exit(2);
+	}
+	buffer=(Uint8 *)screen->pixels;
+	for ( i=0; i<screen->h; ++i ) {
+		memset(buffer,(i*255)/screen->h, screen->pitch);
+		buffer += screen->pitch;
+	}
+	SDL_UnlockSurface(screen);
+	SDL_UpdateRect(screen, 0, 0, 0, 0);
+
+	/* Create the light */
+	light = CreateLight(screen, 82);
+	if ( light == NULL ) {
+		exit(1);
+	}
+
+	/* Load the sprite */
+	if ( LoadSprite(screen, "icon.bmp") < 0 ) {
+		SDL_FreeSurface(light);
+		exit(1);
+	}
+
+	/* Set a clipping rectangle to clip the outside edge of the screen */
+	{ SDL_Rect clip;
+		clip.x = 32;
+		clip.y = 32;
+		clip.w = screen->w-(2*32);
+		clip.h = screen->h-(2*32);
+		SDL_SetClipRect(screen, &clip);
+	}
+
+	/* Wait for a keystroke */
+	lastticks = SDL_GetTicks();
+	done = 0;
+	mouse_pressed = 0;
+	while ( !done ) {
+		/* Update the frame -- move the sprite */
+		if ( mouse_pressed ) {
+			MoveSprite(screen, light);
+			mouse_pressed = 0;
+		} else {
+			MoveSprite(screen, NULL);
+		}
+
+		/* Slow down the loop to 30 frames/second */
+		ticks = SDL_GetTicks();
+		if ( (ticks-lastticks) < FRAME_TICKS ) {
+#ifdef CHECK_SLEEP_GRANULARITY
+fprintf(stderr, "Sleeping %d ticks\n", FRAME_TICKS-(ticks-lastticks));
+#endif
+			SDL_Delay(FRAME_TICKS-(ticks-lastticks));
+#ifdef CHECK_SLEEP_GRANULARITY
+fprintf(stderr, "Slept %d ticks\n", (SDL_GetTicks()-ticks));
+#endif
+		}
+		lastticks = ticks;
+
+		/* Check for events */
+		while ( SDL_PollEvent(&event) ) {
+			switch (event.type) {
+				/* Attract sprite while mouse is held down */
+				case SDL_MOUSEMOTION:
+					if (event.motion.state != 0) {
+						AttractSprite(event.motion.x,
+								event.motion.y);
+						mouse_pressed = 1;
+					}
+					break;
+				case SDL_MOUSEBUTTONDOWN:
+					if ( event.button.button == 1 ) {
+						AttractSprite(event.button.x,
+						              event.button.y);
+						mouse_pressed = 1;
+					} else {
+						SDL_Rect area;
+
+						area.x = event.button.x-16;
+						area.y = event.button.y-16;
+						area.w = 32;
+						area.h = 32;
+						SDL_FillRect(screen, &area, 0);
+						SDL_UpdateRects(screen,1,&area);
+					}
+					break;
+				case SDL_KEYDOWN:
+					/* Any keypress quits the app... */
+				case SDL_QUIT:
+					done = 1;
+					break;
+				default:
+					break;
+			}
+		}
+	}
+	SDL_FreeSurface(light);
+	SDL_FreeSurface(sprite);
+	SDL_FreeSurface(backing);
+
+	/* Print out some timing information */
+	if ( flashes > 0 ) {
+		printf("%d alpha blits, ~%4.4f ms per blit\n", 
+			flashes, (float)flashtime/flashes);
+	}
+	return(0);
+}