test/testalpha.c
author Ryan C. Gordon <icculus@icculus.org>
Fri, 13 Jan 2006 02:32:07 +0000
changeset 1246 ca51a76a7328
parent 1152 51a8702d8ecd
child 1293 23b1ef7d003b
permissions -rw-r--r--
Make error message meaningful if dlopen() fails on libX11.
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/* Simple program:  Fill a colormap with gray and stripe it down the screen,
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		    Then move an alpha valued sprite around the screen.
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 */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include "SDL.h"
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#define FRAME_TICKS	(1000/30)		/* 30 frames/second */
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/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */
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static void quit(int rc)
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{
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	SDL_Quit();
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	exit(rc);
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}
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/* Create a "light" -- a yellowish surface with variable alpha */
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SDL_Surface *CreateLight(SDL_Surface *screen, int radius)
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{
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	Uint8  trans, alphamask;
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	int    range, addition;
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	int    xdist, ydist;
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	Uint16 x, y;
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	Uint16 skip;
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	Uint32 pixel;
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	SDL_Surface *light;
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#ifdef LIGHT_16BIT
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	Uint16 *buf;
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	/* Create a 16 (4/4/4/4) bpp square with a full 4-bit alpha channel */
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	/* Note: this isn't any faster than a 32 bit alpha surface */
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	alphamask = 0x0000000F;
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	light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 16,
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			0x0000F000, 0x00000F00, 0x000000F0, alphamask);
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#else
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	Uint32 *buf;
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	/* Create a 32 (8/8/8/8) bpp square with a full 8-bit alpha channel */
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	alphamask = 0x000000FF;
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	light = SDL_CreateRGBSurface(SDL_SWSURFACE, 2*radius, 2*radius, 32,
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			0xFF000000, 0x00FF0000, 0x0000FF00, alphamask);
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	if ( light == NULL ) {
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		fprintf(stderr, "Couldn't create light: %s\n", SDL_GetError());
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		return(NULL);
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	}
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#endif
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	/* Fill with a light yellow-orange color */
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	skip = light->pitch-(light->w*light->format->BytesPerPixel);
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#ifdef LIGHT_16BIT
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	buf = (Uint16 *)light->pixels;
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#else
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	buf = (Uint32 *)light->pixels;
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#endif
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        /* Get a tranparent pixel value - we'll add alpha later */
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	pixel = SDL_MapRGBA(light->format, 0xFF, 0xDD, 0x88, 0);
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	for ( y=0; y<light->h; ++y ) {
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		for ( x=0; x<light->w; ++x ) {
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			*buf++ = pixel;
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		}
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		buf += skip;	/* Almost always 0, but just in case... */
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	}
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	/* Calculate alpha values for the surface. */
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#ifdef LIGHT_16BIT
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	buf = (Uint16 *)light->pixels;
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#else
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	buf = (Uint32 *)light->pixels;
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#endif
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	for ( y=0; y<light->h; ++y ) {
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		for ( x=0; x<light->w; ++x ) {
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			/* Slow distance formula (from center of light) */
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			xdist = x-(light->w/2);
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			ydist = y-(light->h/2);
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			range = (int)sqrt(xdist*xdist+ydist*ydist);
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			/* Scale distance to range of transparency (0-255) */
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			if ( range > radius ) {
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				trans = alphamask;
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			} else {
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				/* Increasing transparency with distance */
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				trans = (Uint8)((range*alphamask)/radius);
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				/* Lights are very transparent */
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				addition = (alphamask+1)/8;
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				if ( (int)trans+addition > alphamask ) {
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					trans = alphamask;
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				} else {
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					trans += addition;
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				}
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			}
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			/* We set the alpha component as the right N bits */
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			*buf++ |= (255-trans);
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		}
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		buf += skip;	/* Almost always 0, but just in case... */
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	}
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	/* Enable RLE acceleration of this alpha surface */
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	SDL_SetAlpha(light, SDL_SRCALPHA|SDL_RLEACCEL, 0);
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	/* We're done! */
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	return(light);
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}
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static Uint32 flashes = 0;
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static Uint32 flashtime = 0;
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void FlashLight(SDL_Surface *screen, SDL_Surface *light, int x, int y)
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{
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	SDL_Rect position;
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	Uint32   ticks1;
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	Uint32   ticks2;
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	/* Easy, center light */
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	position.x = x-(light->w/2);
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	position.y = y-(light->h/2);
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	position.w = light->w;
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	position.h = light->h;
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	ticks1 = SDL_GetTicks();
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	SDL_BlitSurface(light, NULL, screen, &position);
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	ticks2 = SDL_GetTicks();
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	SDL_UpdateRects(screen, 1, &position);
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	++flashes;
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	/* Update time spend doing alpha blitting */
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	flashtime += (ticks2-ticks1);
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}
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static int sprite_visible = 0;
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static SDL_Surface *sprite;
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static SDL_Surface *backing;
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static SDL_Rect    position;
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static int         x_vel, y_vel;
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static int	   alpha_vel;
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int LoadSprite(SDL_Surface *screen, char *file)
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{
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	SDL_Surface *converted;
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	/* Load the sprite image */
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	sprite = SDL_LoadBMP(file);
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	if ( sprite == NULL ) {
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		fprintf(stderr, "Couldn't load %s: %s", file, SDL_GetError());
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		return(-1);
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	}
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	/* Set transparent pixel as the pixel at (0,0) */
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	if ( sprite->format->palette ) {
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		SDL_SetColorKey(sprite, SDL_SRCCOLORKEY,
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						*(Uint8 *)sprite->pixels);
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	}
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	/* Convert sprite to video format */
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	converted = SDL_DisplayFormat(sprite);
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	SDL_FreeSurface(sprite);
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	if ( converted == NULL ) {
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		fprintf(stderr, "Couldn't convert background: %s\n",
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							SDL_GetError());
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		return(-1);
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	}
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	sprite = converted;
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	/* Create the background */
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	backing = SDL_CreateRGBSurface(SDL_SWSURFACE, sprite->w, sprite->h, 8,
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								0, 0, 0, 0);
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	if ( backing == NULL ) {
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		fprintf(stderr, "Couldn't create background: %s\n",
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							SDL_GetError());
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		SDL_FreeSurface(sprite);
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		return(-1);
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	}
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	/* Convert background to video format */
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	converted = SDL_DisplayFormat(backing);
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	SDL_FreeSurface(backing);
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	if ( converted == NULL ) {
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		fprintf(stderr, "Couldn't convert background: %s\n",
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							SDL_GetError());
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		SDL_FreeSurface(sprite);
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		return(-1);
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	}
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	backing = converted;
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	/* Set the initial position of the sprite */
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	position.x = (screen->w-sprite->w)/2;
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	position.y = (screen->h-sprite->h)/2;
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	position.w = sprite->w;
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	position.h = sprite->h;
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	x_vel = 0; y_vel = 0;
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	alpha_vel = 1;
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	/* We're ready to roll. :) */
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	return(0);
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}
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void AttractSprite(Uint16 x, Uint16 y)
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{
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	x_vel = ((int)x-position.x)/10;
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	y_vel = ((int)y-position.y)/10;
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}
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void MoveSprite(SDL_Surface *screen, SDL_Surface *light)
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{
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	SDL_Rect updates[2];
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	int alpha;
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	/* Erase the sprite if it was visible */
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	if ( sprite_visible ) {
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		updates[0] = position;
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		SDL_BlitSurface(backing, NULL, screen, &updates[0]);
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	} else {
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		updates[0].x = 0; updates[0].y = 0;
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		updates[0].w = 0; updates[0].h = 0;
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		sprite_visible = 1;
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	}
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	/* Since the sprite is off the screen, we can do other drawing
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	   without being overwritten by the saved area behind the sprite.
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	 */
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	if ( light != NULL ) {
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		int x, y;
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		SDL_GetMouseState(&x, &y);
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		FlashLight(screen, light, x, y);
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	}
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	/* Move the sprite, bounce at the wall */
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	position.x += x_vel;
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	if ( (position.x < 0) || (position.x >= screen->w) ) {
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		x_vel = -x_vel;
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		position.x += x_vel;
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	}
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	position.y += y_vel;
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	if ( (position.y < 0) || (position.y >= screen->h) ) {
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		y_vel = -y_vel;
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		position.y += y_vel;
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	}
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	/* Update transparency (fade in and out) */
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	alpha = sprite->format->alpha;
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	if ( (alpha+alpha_vel) < 0 ) {
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		alpha_vel = -alpha_vel;
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	} else
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	if ( (alpha+alpha_vel) > 255 ) {
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		alpha_vel = -alpha_vel;
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	}
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	SDL_SetAlpha(sprite, SDL_SRCALPHA, (Uint8)(alpha+alpha_vel));
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	/* Save the area behind the sprite */
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	updates[1] = position;
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	SDL_BlitSurface(screen, &updates[1], backing, NULL);
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	/* Blit the sprite onto the screen */
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	updates[1] = position;
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	SDL_BlitSurface(sprite, NULL, screen, &updates[1]);
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	/* Make it so! */
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	SDL_UpdateRects(screen, 2, updates);
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}
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void WarpSprite(SDL_Surface *screen, int x, int y)
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{
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	SDL_Rect updates[2];
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	/* Erase, move, Draw, update */
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	updates[0] = position;
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	SDL_BlitSurface(backing, NULL, screen, &updates[0]);
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	position.x = x-sprite->w/2;	/* Center about X */
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	position.y = y-sprite->h/2;	/* Center about Y */
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	updates[1] = position;
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	SDL_BlitSurface(screen, &updates[1], backing, NULL);
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	updates[1] = position;
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	SDL_BlitSurface(sprite, NULL, screen, &updates[1]);
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	SDL_UpdateRects(screen, 2, updates);
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}
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int main(int argc, char *argv[])
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{
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	const SDL_VideoInfo *info;
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	SDL_Surface *screen;
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	Uint8  video_bpp;
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	Uint32 videoflags;
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	Uint8 *buffer;
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	int    i, k, done;
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	SDL_Event event;
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	SDL_Surface *light;
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	int mouse_pressed;
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	Uint32 ticks, lastticks;
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	Uint16 *buffer16;
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        Uint16 color;
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        Uint8  gradient;
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	/* Initialize SDL */
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	if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
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		fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());
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		return(1);
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	}
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	/* Alpha blending doesn't work well at 8-bit color */
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	info = SDL_GetVideoInfo();
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	if ( info->vfmt->BitsPerPixel > 8 ) {
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		video_bpp = info->vfmt->BitsPerPixel;
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	} else {
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		video_bpp = 16;
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                fprintf(stderr, "forced 16 bpp mode\n");
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	}
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	videoflags = SDL_SWSURFACE;
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	while ( argc > 1 ) {
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		--argc;
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		if ( strcmp(argv[argc-1], "-bpp") == 0 ) {
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			video_bpp = atoi(argv[argc]);
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                        if (video_bpp<=8) {
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                            video_bpp=16;
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                            fprintf(stderr, "forced 16 bpp mode\n");
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                        }
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			--argc;
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		} else
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		if ( strcmp(argv[argc], "-hw") == 0 ) {
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			videoflags |= SDL_HWSURFACE;
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		} else
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		if ( strcmp(argv[argc], "-warp") == 0 ) {
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			videoflags |= SDL_HWPALETTE;
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		} else
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		if ( strcmp(argv[argc], "-fullscreen") == 0 ) {
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			videoflags |= SDL_FULLSCREEN;
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		} else {
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			fprintf(stderr, 
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			"Usage: %s [-bpp N] [-warp] [-hw] [-fullscreen]\n",
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								argv[0]);
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			quit(1);
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		}
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	}
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	/* Set 640x480 video mode */
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#ifndef _WIN32_WCE
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	if ( (screen=SDL_SetVideoMode(640,480,video_bpp,videoflags)) == NULL ) {
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		fprintf(stderr, "Couldn't set 640x480x%d video mode: %s\n",
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						video_bpp, SDL_GetError());
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		quit(2);
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	}
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#else
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	/* Pocket PC */
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	if ( (screen=SDL_SetVideoMode(240,320,video_bpp,SDL_FULLSCREEN)) == NULL ) {
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		fprintf(stderr, "Couldn't set 240x320x%d video mode: %s\n",
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						video_bpp, SDL_GetError());
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		quit(2);
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	}
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#endif
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	/* Set the surface pixels and refresh! */
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	if ( SDL_LockSurface(screen) < 0 ) {
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		fprintf(stderr, "Couldn't lock the display surface: %s\n",
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							SDL_GetError());
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		quit(2);
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	}
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	buffer=(Uint8 *)screen->pixels;
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	if (screen->format->BytesPerPixel!=2) {
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		for ( i=0; i<screen->h; ++i ) {
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			memset(buffer,(i*255)/screen->h, screen->pitch);
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			buffer += screen->pitch;
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		}
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	}
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        else
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        {
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   371
		for ( i=0; i<screen->h; ++i ) {
slouken@691
   372
			gradient=((i*255)/screen->h);
slouken@691
   373
                        color = SDL_MapRGB(screen->format, gradient, gradient, gradient);
slouken@691
   374
                        buffer16=(Uint16*)buffer;
slouken@691
   375
                        for (k=0; k<screen->w; k++)
slouken@691
   376
                        {
slouken@691
   377
                            *(buffer16+k)=color;
slouken@691
   378
                        }
slouken@691
   379
			buffer += screen->pitch;
slouken@691
   380
		}
slouken@691
   381
        }
slouken@691
   382
slouken@0
   383
	SDL_UnlockSurface(screen);
slouken@0
   384
	SDL_UpdateRect(screen, 0, 0, 0, 0);
slouken@0
   385
slouken@0
   386
	/* Create the light */
slouken@0
   387
	light = CreateLight(screen, 82);
slouken@0
   388
	if ( light == NULL ) {
icculus@1151
   389
		quit(1);
slouken@0
   390
	}
slouken@0
   391
slouken@0
   392
	/* Load the sprite */
slouken@0
   393
	if ( LoadSprite(screen, "icon.bmp") < 0 ) {
slouken@0
   394
		SDL_FreeSurface(light);
icculus@1151
   395
		quit(1);
slouken@0
   396
	}
slouken@0
   397
slouken@886
   398
	/* Print out information about our surfaces */
slouken@886
   399
	printf("Screen is at %d bits per pixel\n",screen->format->BitsPerPixel);
slouken@886
   400
	if ( (screen->flags & SDL_HWSURFACE) == SDL_HWSURFACE ) {
slouken@886
   401
		printf("Screen is in video memory\n");
slouken@886
   402
	} else {
slouken@886
   403
		printf("Screen is in system memory\n");
slouken@886
   404
	}
slouken@886
   405
	if ( (screen->flags & SDL_DOUBLEBUF) == SDL_DOUBLEBUF ) {
slouken@886
   406
		printf("Screen has double-buffering enabled\n");
slouken@886
   407
	}
slouken@886
   408
	if ( (sprite->flags & SDL_HWSURFACE) == SDL_HWSURFACE ) {
slouken@886
   409
		printf("Sprite is in video memory\n");
slouken@886
   410
	} else {
slouken@886
   411
		printf("Sprite is in system memory\n");
slouken@886
   412
	}
slouken@886
   413
slouken@886
   414
	/* Run a sample blit to trigger blit acceleration */
slouken@886
   415
	{ SDL_Rect dst;
slouken@886
   416
		dst.x = 0;
slouken@886
   417
		dst.y = 0;
slouken@886
   418
		dst.w = sprite->w;
slouken@886
   419
		dst.h = sprite->h;
slouken@886
   420
		SDL_BlitSurface(sprite, NULL, screen, &dst);
slouken@886
   421
		SDL_FillRect(screen, &dst, 0);
slouken@886
   422
	}
slouken@886
   423
	if ( (sprite->flags & SDL_HWACCEL) == SDL_HWACCEL ) {
slouken@886
   424
		printf("Sprite blit uses hardware alpha acceleration\n");
slouken@886
   425
	} else {
slouken@886
   426
		printf("Sprite blit dosn't uses hardware alpha acceleration\n");
slouken@886
   427
	}
slouken@886
   428
slouken@0
   429
	/* Set a clipping rectangle to clip the outside edge of the screen */
slouken@0
   430
	{ SDL_Rect clip;
slouken@0
   431
		clip.x = 32;
slouken@0
   432
		clip.y = 32;
slouken@0
   433
		clip.w = screen->w-(2*32);
slouken@0
   434
		clip.h = screen->h-(2*32);
slouken@0
   435
		SDL_SetClipRect(screen, &clip);
slouken@0
   436
	}
slouken@0
   437
slouken@0
   438
	/* Wait for a keystroke */
slouken@0
   439
	lastticks = SDL_GetTicks();
slouken@0
   440
	done = 0;
slouken@0
   441
	mouse_pressed = 0;
slouken@0
   442
	while ( !done ) {
slouken@0
   443
		/* Update the frame -- move the sprite */
slouken@0
   444
		if ( mouse_pressed ) {
slouken@0
   445
			MoveSprite(screen, light);
slouken@0
   446
			mouse_pressed = 0;
slouken@0
   447
		} else {
slouken@0
   448
			MoveSprite(screen, NULL);
slouken@0
   449
		}
slouken@0
   450
slouken@0
   451
		/* Slow down the loop to 30 frames/second */
slouken@0
   452
		ticks = SDL_GetTicks();
slouken@0
   453
		if ( (ticks-lastticks) < FRAME_TICKS ) {
slouken@0
   454
#ifdef CHECK_SLEEP_GRANULARITY
slouken@0
   455
fprintf(stderr, "Sleeping %d ticks\n", FRAME_TICKS-(ticks-lastticks));
slouken@0
   456
#endif
slouken@0
   457
			SDL_Delay(FRAME_TICKS-(ticks-lastticks));
slouken@0
   458
#ifdef CHECK_SLEEP_GRANULARITY
slouken@0
   459
fprintf(stderr, "Slept %d ticks\n", (SDL_GetTicks()-ticks));
slouken@0
   460
#endif
slouken@0
   461
		}
slouken@0
   462
		lastticks = ticks;
slouken@0
   463
slouken@0
   464
		/* Check for events */
slouken@0
   465
		while ( SDL_PollEvent(&event) ) {
slouken@0
   466
			switch (event.type) {
slouken@0
   467
				/* Attract sprite while mouse is held down */
slouken@0
   468
				case SDL_MOUSEMOTION:
slouken@0
   469
					if (event.motion.state != 0) {
slouken@0
   470
						AttractSprite(event.motion.x,
slouken@0
   471
								event.motion.y);
slouken@0
   472
						mouse_pressed = 1;
slouken@0
   473
					}
slouken@0
   474
					break;
slouken@0
   475
				case SDL_MOUSEBUTTONDOWN:
slouken@0
   476
					if ( event.button.button == 1 ) {
slouken@0
   477
						AttractSprite(event.button.x,
slouken@0
   478
						              event.button.y);
slouken@0
   479
						mouse_pressed = 1;
slouken@0
   480
					} else {
slouken@0
   481
						SDL_Rect area;
slouken@0
   482
slouken@0
   483
						area.x = event.button.x-16;
slouken@0
   484
						area.y = event.button.y-16;
slouken@0
   485
						area.w = 32;
slouken@0
   486
						area.h = 32;
slouken@0
   487
						SDL_FillRect(screen, &area, 0);
slouken@0
   488
						SDL_UpdateRects(screen,1,&area);
slouken@0
   489
					}
slouken@0
   490
					break;
slouken@0
   491
				case SDL_KEYDOWN:
slouken@0
   492
					/* Any keypress quits the app... */
slouken@0
   493
				case SDL_QUIT:
slouken@0
   494
					done = 1;
slouken@0
   495
					break;
slouken@0
   496
				default:
slouken@0
   497
					break;
slouken@0
   498
			}
slouken@0
   499
		}
slouken@0
   500
	}
slouken@0
   501
	SDL_FreeSurface(light);
slouken@0
   502
	SDL_FreeSurface(sprite);
slouken@0
   503
	SDL_FreeSurface(backing);
slouken@0
   504
slouken@0
   505
	/* Print out some timing information */
slouken@0
   506
	if ( flashes > 0 ) {
slouken@0
   507
		printf("%d alpha blits, ~%4.4f ms per blit\n", 
slouken@0
   508
			flashes, (float)flashtime/flashes);
slouken@0
   509
	}
icculus@1151
   510
icculus@1151
   511
	SDL_Quit();
slouken@0
   512
	return(0);
slouken@0
   513
}