/* 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 */
/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */
static void quit(int rc)
{
SDL_Quit();
exit(rc);
}
/* Fill the screen with a gradient */
static void FillBackground(SDL_Surface *screen)
{
Uint8 *buffer;
Uint16 *buffer16;
Uint16 color;
Uint8 gradient;
int i, k;
/* Set the surface pixels and refresh! */
if ( SDL_LockSurface(screen) < 0 ) {
fprintf(stderr, "Couldn't lock the display surface: %s\n",
SDL_GetError());
quit(2);
}
buffer=(Uint8 *)screen->pixels;
if (screen->format->BytesPerPixel!=2) {
for ( i=0; i<screen->h; ++i ) {
memset(buffer,(i*255)/screen->h, screen->w*screen->format->BytesPerPixel);
buffer += screen->pitch;
}
}
else
{
for ( i=0; i<screen->h; ++i ) {
gradient=((i*255)/screen->h);
color = (Uint16)SDL_MapRGB(screen->format, gradient, gradient, gradient);
buffer16=(Uint16*)buffer;
for (k=0; k<screen->w; k++)
{
*(buffer16+k)=color;
}
buffer += screen->pitch;
}
}
SDL_UnlockSurface(screen);
SDL_UpdateRect(screen, 0, 0, 0, 0);
}
/* Create a "light" -- a yellowish surface with variable alpha */
SDL_Surface *CreateLight(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;
int w, h;
Uint8 video_bpp;
Uint32 videoflags;
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());
return(1);
}
/* Alpha blending doesn't work well at 8-bit color */
#ifdef _WIN32_WCE
/* Pocket PC */
w = 240;
h = 320;
#else
w = 640;
h = 480;
#endif
info = SDL_GetVideoInfo();
if ( info->vfmt->BitsPerPixel > 8 ) {
video_bpp = info->vfmt->BitsPerPixel;
} else {
video_bpp = 16;
fprintf(stderr, "forced 16 bpp mode\n");
}
videoflags = SDL_SWSURFACE;
for ( i = 1; argv[i]; ++i ) {
if ( strcmp(argv[i], "-bpp") == 0 ) {
video_bpp = atoi(argv[++i]);
if (video_bpp<=8) {
video_bpp=16;
fprintf(stderr, "forced 16 bpp mode\n");
}
} else
if ( strcmp(argv[i], "-hw") == 0 ) {
videoflags |= SDL_HWSURFACE;
} else
if ( strcmp(argv[i], "-warp") == 0 ) {
videoflags |= SDL_HWPALETTE;
} else
if ( strcmp(argv[i], "-width") == 0 && argv[i+1] ) {
w = atoi(argv[++i]);
} else
if ( strcmp(argv[i], "-height") == 0 && argv[i+1] ) {
h = atoi(argv[++i]);
} else
if ( strcmp(argv[i], "-resize") == 0 ) {
videoflags |= SDL_RESIZABLE;
} else
if ( strcmp(argv[i], "-noframe") == 0 ) {
videoflags |= SDL_NOFRAME;
} else
if ( strcmp(argv[i], "-fullscreen") == 0 ) {
videoflags |= SDL_FULLSCREEN;
} else {
fprintf(stderr,
"Usage: %s [-width N] [-height N] [-bpp N] [-warp] [-hw] [-fullscreen]\n",
argv[0]);
quit(1);
}
}
/* Set video mode */
if ( (screen=SDL_SetVideoMode(w,h,video_bpp,videoflags)) == NULL ) {
fprintf(stderr, "Couldn't set %dx%dx%d video mode: %s\n",
w, h, video_bpp, SDL_GetError());
quit(2);
}
FillBackground(screen);
/* Create the light */
light = CreateLight(82);
if ( light == NULL ) {
quit(1);
}
/* Load the sprite */
if ( LoadSprite(screen, "icon.bmp") < 0 ) {
SDL_FreeSurface(light);
quit(1);
}
/* Print out information about our surfaces */
printf("Screen is at %d bits per pixel\n",screen->format->BitsPerPixel);
if ( (screen->flags & SDL_HWSURFACE) == SDL_HWSURFACE ) {
printf("Screen is in video memory\n");
} else {
printf("Screen is in system memory\n");
}
if ( (screen->flags & SDL_DOUBLEBUF) == SDL_DOUBLEBUF ) {
printf("Screen has double-buffering enabled\n");
}
if ( (sprite->flags & SDL_HWSURFACE) == SDL_HWSURFACE ) {
printf("Sprite is in video memory\n");
} else {
printf("Sprite is in system memory\n");
}
/* Run a sample blit to trigger blit acceleration */
MoveSprite(screen, NULL);
if ( (sprite->flags & SDL_HWACCEL) == SDL_HWACCEL ) {
printf("Sprite blit uses hardware alpha acceleration\n");
} else {
printf("Sprite blit dosn't uses hardware alpha acceleration\n");
}
/* 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) {
case SDL_VIDEORESIZE:
screen = SDL_SetVideoMode(event.resize.w, event.resize.h, video_bpp, videoflags);
if ( screen ) {
FillBackground(screen);
}
break;
/* 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:
#ifndef _WIN32_WCE
if ( event.key.keysym.sym == SDLK_ESCAPE ) {
done = 1;
}
#else
// there is no ESC key at all
done = 1;
#endif
break;
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);
}
SDL_Quit();
return(0);
}