#include <string.h>
#include <stdlib.h>
#include "SDL/SDL.h"
 
SDL_Surface *screen;
 
typedef struct {
    SDL_Surface *image;
    SDL_Surface *bgsave;
    Uint16 x;
    Uint16 y;
    Uint16 ox;
    Uint16 oy;
} sprite, *sprite_ptr;
 
void RS_Blit(SDL_Surface *bitmap, Sint16 x, Sint16 y);
void play_game();
SDL_Surface *prep_image(char *file);
 
void draw_sprite(sprite *s);
void erase_sprite(sprite *s);
 
void RS_Blit(SDL_Surface *bitmap, Sint16 x, Sint16 y)
{
    SDL_Rect dest;
    dest.x = x;
    dest.y = y;
    dest.w = bitmap->w;
    dest.h = bitmap->h;
    SDL_BlitSurface(bitmap, NULL, screen, &dest);
}
 
SDL_Surface *prep_image(char *file)
{
    SDL_Surface *image;
 
    image=SDL_LoadBMP(file);
    return(image);
}
 
void get_bg(SDL_Surface *surface, int x, int y)
{
    /* Blits a surface sized chunk of background to that surface */
    SDL_Rect src;
    SDL_Rect dst;
 
    src.x = x;
    src.y = y;
    src.w = surface->w;
    src.h = surface->h;
 
    dst.x = 0;
    dst.y = 0;
    dst.w = surface->w;
    dst.h = surface->h;
    SDL_BlitSurface(screen, &src, surface, &dst);
}
 
int main(int argc, char *argv[])
{
 
    SDL_Init(SDL_INIT_VIDEO);
    screen = SDL_SetVideoMode(640, 480, 0, SDL_SWSURFACE);
    play_game();
    SDL_Quit();
    exit(0);
}
 
void play_game()
{
    SDL_Event event;
    Uint8 *keys;
    int x, y;
    int ox, oy;
    int done=0, translucent=0;
 
    /* The buttons and mouse cursor surfaces */
    SDL_Surface *button1;
    SDL_Surface *button2;
    SDL_Surface *cursor;
 
    /* Used to hold background oblitered when mouse is blitted */
 
    SDL_Surface *cursor_save;
 
    /* Hide the existing cursor */
 
    SDL_ShowCursor(0);
 
    /* Load the cursor, and set the color key (100% blue for this one) */
 
    cursor=prep_image("cursor.bmp");
    SDL_SetColorKey(cursor, SDL_SRCCOLORKEY|SDL_RLEACCEL,SDL_MapRGB(cursor->format, 0, 0, 255));
 
    /* Set up the save, by loading the cursor image it makes sure it is the
    same size.  This should'nt be color keyed */
 
    cursor_save=prep_image("cursor.bmp");
 
    /* Load the buttons */
    button1=prep_image("button1.bmp");
    button2=prep_image("button2.bmp");
 
    x=0;
    y=0;
    get_bg(cursor_save, x, y);
 
    RS_Blit(button2, 0, 0);
    RS_Blit(button1, 640-button1->w, 480-button1->h);
    SDL_UpdateRect(screen,0, 0, 0, 0);
 
    do {
        SDL_GetMouseState(&x, &y);
        while ( SDL_PollEvent(&event) ) {
            ox = x;
            oy = y; /* Save old values for erasing the cursor */
            if ( event.type == SDL_QUIT )
                done=1;
 
            if ( event.type == SDL_MOUSEBUTTONDOWN ) {
                if( (x>640-button1->w)&&(x<640) ) {
                    if ((y>480-button1->h)&&(y<480))
                        done=1;
                }
 
                if( (x>0)&&(x<button2->w) ) {
                    if ((y>0)&&(y<button2->h)) {
                        if(translucent) {
                            SDL_SetAlpha(cursor, SDL_SRCALPHA, 0);
                            translucent=0;
                        } else {
                            SDL_SetAlpha(cursor, SDL_SRCALPHA, 127);
                            translucent=1;
                        }
                    }
                }
            }
        }
 
        keys = SDL_GetKeyState(NULL);
        if(keys[SDLK_ESCAPE] == SDL_PRESSED)
            done=1;
 
        /* Draw anything to the screen before drawing the cursor, or
        else the cursor may be covered or and it may not restore the
        background correctly */
 
        get_bg(cursor_save, x, y);
        RS_Blit(cursor, x, y);
 
        /* In real life redrawing the whole screen is bad (read as "slow") */
        SDL_UpdateRect(screen,0, 0, 0, 0);
        RS_Blit(cursor_save, x, y);
    } while(!done);
 
    /* Free the surfaces */
    SDL_FreeSurface(button1);
    SDL_FreeSurface(button2);
    SDL_FreeSurface(cursor);
    SDL_FreeSurface(cursor_save);
}