#include <X11/X.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

typedef unsigned long ulong;

#define SIZEX		400
#define SIZEX2		(SIZEX/2)
#define SIZEY		400
#define SIZEY2		(SIZEY/2)

static int SCANSCALE	=64;

static Display		*display;
static Window		window,root;
static XImage		*src,*dest;
static XEvent		ev;
static ulong		black,white;
static int		width,height,cx,cy;
static int		shrink=False;
static GC		gc;

int main(int argc, char *argv[])
{
    void ScaleImg(XImage *dest, XImage *src);
    char str[180];
    Window rw,cw;
    int rx,ry,cx,cy,bmask;
    int f;

    if (argc>1)
	if (!strcmp(argv[1],"-help"))
	{
	    fprintf(stderr,"Keys :\n");
	    fprintf(stderr,"LMB -  Lower viewing angle\n");
	    fprintf(stderr,"MMB -  Raise viewing angle\n");
	    fprintf(stderr,"RMB -  Quit\n");
	}

    if (!(display=XOpenDisplay(NULL)))
    {
	fprintf(stderr,"%s: couldn't open display\n",argv[0]);
	exit(1);
    }

    root=DefaultRootWindow(display);
    root=RootWindow(display,DefaultScreen(display));
    width=DisplayWidth(display,DefaultScreen(display));
    height=DisplayHeight(display,DefaultScreen(display));

    window=XCreateSimpleWindow (display,root,0,800,SIZEX,SIZEY,0,0,0);

    gc=XCreateGC(display,window,0L,NULL);

    XSetBackground(display,gc,white=WhitePixel(display,0));
    XSetForeground(display,gc,black=BlackPixel(display,0));
    XSetPlaneMask(display,gc,AllPlanes);

    XSelectInput (display,window,ButtonPressMask);
    XMapWindow(display,window);

    while(True)
    {
	if (XCheckTypedWindowEvent(display,window,ButtonPress,&ev))
	    switch(ev.xbutton.button)
	    {
		case 1:
		    SCANSCALE=SCANSCALE>>1;

		    if (SCANSCALE<1)
			SCANSCALE=1;
		    break;

		case 2:
		    SCANSCALE=SCANSCALE<<1;
		    break;

		case 3:
		    XCloseDisplay(display);
		    exit(0);
		    break;
	    }

	XQueryPointer(display,window,&rw,&cw,&rx,&ry,&cx,&cy,&bmask);

	rx-=SIZEX/2;
	ry-=SIZEY/2;

	if (rx<0)
	    rx=0;

	if (ry<0)
	    ry=0;

	if ((rx+SIZEX)>=width)
	    rx=width-SIZEX;

	if ((ry+SIZEY)>=height)
	    ry=height-SIZEY;

	src=XGetImage(display,root,rx,ry,SIZEX,SIZEY,AllPlanes,ZPixmap);

	/* Cheat to create an image we know will be the same as the source...
	*/
	dest=XGetImage(display,root,0,0,SIZEX,SIZEY,AllPlanes,ZPixmap);

	ScaleImg(src,dest);

	XPutImage(display,window,gc,dest,0,0,0,0,SIZEX,SIZEY);

	XDestroyImage (src);
	XDestroyImage (dest);
	/* XSync(display,False); */
    }
}


int ScaleX (double n, double sc)
{
    return SIZEX2-(int)((SIZEX2-n)/sc);
}


int ScaleY (double n, double sc)
{
    return SIZEY2-(int)((SIZEY2-n)/sc);
}


void ScaleImg(XImage *src, XImage *dest)
{
    int x,y;
    double sc;

    sc=1.0;

    for(y=0;y<SIZEY;y++)
    {
	for(x=0;x<SIZEX;x++)
		if (sc==1)
		    XPutPixel(dest,x,y,XGetPixel(src,x,y));
		else
		    XPutPixel(dest,x,y,XGetPixel(src,ScaleX((double)x,sc),
						 ScaleY((double)y,sc)));

	sc+=(1.0/SCANSCALE);
    }
}