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

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

extern const char *__progname;

static Display *disp;
static Screen *scr;
static int depth;
static Window rootwin;
static Colormap wincmap;
static int defcmap;
static GC gc;
static XVisualInfo visinfo;
static Window win;
static unsigned long int *imgdata;
static XImage *img;

#include "readloop-X.h"

static void find_visual(void)
{
 XVisualInfo *xvi;
 int nvi;
 XVisualInfo template;
 int i;
 int best;
 int best_onscr;

 template.class = TrueColor;
 xvi = XGetVisualInfo(disp,VisualClassMask,&template,&nvi);
 best = -1;
 best_onscr = -1;
 for (i=0;i<nvi;i++)
  { if (xvi[i].screen == XDefaultScreen(disp))
     { if ( (best_onscr < 0) ||
	    (xvi[i].depth > xvi[best_onscr].depth) ||
	    ( (xvi[i].depth == xvi[best_onscr].depth) &&
	      (xvi[i].visual == XDefaultVisual(disp,xvi[i].screen)) ) )
	{ best_onscr = i;
	}
     }
    if ( (best < 0) ||
	 (xvi[i].depth > xvi[best].depth) ||
	 ( (xvi[i].depth == xvi[best].depth) &&
	   (xvi[i].visual == XDefaultVisual(disp,xvi[i].screen)) ) )
     { best = i;
     }
  }
 if (best < 0)
  { fprintf(stderr,"%s: no TrueColor visual available\n",__progname);
    exit(1);
  }
 if (best_onscr < 0)
  { fprintf(stderr,"%s: no TrueColor visual on screen %d, using screen %d\n",__progname,XDefaultScreen(disp),xvi[best].screen);
  }
 else
  { best = best_onscr;
  }
 visinfo = xvi[best];
}

static void setup_gc(void)
{
 if (depth == XDefaultDepthOfScreen(scr))
  { gc = XDefaultGCOfScreen(scr);
  }
 else
  { Pixmap p;
    p = XCreatePixmap(disp,rootwin,1,1,depth);
    gc = XCreateGC(disp,p,0,0);
    XFreePixmap(disp,p);
  }
}

static void setup_cmap(void)
{
 if (visinfo.visual == XDefaultVisualOfScreen(scr))
  { wincmap = XDefaultColormapOfScreen(scr);
    defcmap = 1;
  }
 else
  { wincmap = XCreateColormap(disp,rootwin,visinfo.visual,AllocNone);
    defcmap = 0;
  }
}

static void setup_image(void)
{
 imgdata = malloc(640*480*4);
 img = XCreateImage(disp,visinfo.visual,depth,ZPixmap,0,(void *)imgdata,640,480,32,640*4);
 img->byte_order = LSBFirst;
 img->bitmap_unit = 32;
 img->bitmap_bit_order = LSBFirst;
 img->bitmap_pad = 32;
}

static void setup_window(void)
{
 unsigned long int attrmask;
 XSetWindowAttributes attr;

 attrmask = 0;
 attr.background_pixel = ~0U;
 attrmask |= CWBackPixel;
 attr.border_pixel = 0;
 attrmask |= CWBorderPixel;
 attr.backing_store = NotUseful;
 attrmask |= CWBackingStore;
 attr.event_mask = 0;
 attrmask |= CWEventMask;
 attr.colormap = wincmap;
 attrmask |= CWColormap;
 win = XCreateWindow(disp,rootwin,0,0,640,480,0,depth,InputOutput,visinfo.visual,attrmask,&attr);
 XMapRaised(disp,win);
}

static void ping_myself(void)
{
 XEvent e;

 e.type = ClientMessage;
 e.xclient.send_event = True;
 e.xclient.window = win;
 e.xclient.message_type = XA_X_HEIGHT;
 e.xclient.format = 8;
 XSendEvent(disp,win,False,0,&e);
}

static void await_ping(void)
{
 XEvent e;

 do
  { XNextEvent(disp,&e);
  } while (e.type != ClientMessage);
}

void setup_X(void)
{
 disp = XOpenDisplay(0);
 if (disp == 0)
  { fprintf(stderr,"%s: can't open display\n",__progname);
    exit(1);
  }
 find_visual();
 scr = XScreenOfDisplay(disp,visinfo.screen);
 depth = visinfo.depth;
 rootwin = XRootWindowOfScreen(scr);
 setup_gc();
 setup_cmap();
 setup_image();
 setup_window();
 ping_myself();
 XFlush(disp);
}

void display_frame(const unsigned char *dbuf)
{
 int x;
 int y;
 unsigned long int *ip;

 ip = imgdata;
 for (y=0;y<640;y++)
  { for (x=0;x<480;x+=2)
     { *ip++ = 0x00010101 * *dbuf++;
       dbuf ++;
       *ip++ = 0x00010101 * *dbuf++;
       dbuf ++;
     }
  }
 await_ping();
 XPutImage(disp,win,gc,img,0,0,0,0,640,480);
 ping_myself();
 XFlush(disp);
}