#include <X11/Xlib.h>
#include <stdlib.h>
#include <unistd.h>

#include <Xft.h>

void die( char *s) {
    puts( s);

    exit(1);
}

void expose( Display *dpy, Window win,
	XftDraw *xftdraw, XftColor *xftcolor, XftFont *xftfont)
{
    FT_UInt glyphs[16];
    FT_UInt i,j;

    XClearWindow( dpy, win);

    for( i=0; i<16; i++) {
	for( j=0; j<16; j++) {
	    glyphs[j] = 16*i + j;
	}
	XftDrawGlyphs( xftdraw, xftcolor, xftfont, 10,
		10 + xftfont->ascent + (xftfont->ascent + xftfont->descent)*i,
		glyphs, 16);
    }
    // puts( "drew string");
}

int main(int argc, char *argv[]) {
    Display	*dpy;
    int		screen;
    Window	win;

    Visual	*visual;
    Colormap	cmap;

    XftFont	 *xftfont = NULL;
    XftDraw	 *xftdraw;
    XRenderColor color;
    XftColor	 xftcolor;

    XftPattern   *pattern = XftPatternCreate(), *match;
    XftResult	 fr;

    XEvent	ev;

    char *fontname;

    if( argc > 1)
	fontname = argv[1];
    else
	fontname = "Bitstream Vera Sans Mono";

    if( !(dpy = XOpenDisplay(0)) )
	die("Could not open display");

    screen = DefaultScreen( dpy);
    visual = DefaultVisual( dpy, screen);
    cmap   = DefaultColormap( dpy, screen);

    XftPatternAddString(  pattern, XFT_FAMILY, fontname);
    XftPatternAddInteger( pattern, XFT_SIZE, 20);
    XftPatternAddInteger( pattern, XFT_SPACING, XFT_MONO);

    match = XftFontMatch ( dpy, screen, pattern, &fr);
    FcPatternPrint( match);

    xftfont = XftFontOpenPattern( dpy, match);

    /*
     * BUG: XftFontOpenPattern() frees the pattern if it returns an already
     * open font. Thus closing and re-opening the *same* font will cause a
     * segfault when we attempt to acces the pattern match. Commenting the next
     * two lines causes perfect execution.
     */
    XftFontClose( dpy, xftfont);
    xftfont = XftFontOpenPattern( dpy, match);

    XftPatternDestroy( match);
    XftPatternDestroy( pattern);

    win = XCreateSimpleWindow( dpy, DefaultRootWindow(dpy), 0, 0,
	    20 + xftfont->max_advance_width * 16,
	    20 + (xftfont->ascent + xftfont->descent) * 16,
	    0, BlackPixel( dpy, screen), BlackPixel( dpy, screen));

    xftdraw = XftDrawCreate(dpy, win, visual, cmap);

    color.red	= 0xb000;
    color.blue	= 0xb000;
    color.green = 0xb000;
    color.alpha = 0;

    XftColorAllocValue(dpy, visual, cmap, &color, &xftcolor);

    // Wait untill window is mapped
    XSelectInput( dpy, win, ExposureMask | KeyPressMask );
    XMapWindow( dpy, win);

    while(1) {
	XNextEvent( dpy, &ev);

	if( ev.type == KeyPress && ev.xkey.keycode == 24 ) break;
	else if( ev.type == Expose) {
	    while( XCheckTypedWindowEvent( dpy, win, ExposureMask, &ev) );
	    expose(dpy, win, xftdraw, &xftcolor, xftfont);
	}
    };
    
    XftColorFree( dpy, visual, cmap, &xftcolor);
    XftDrawDestroy( xftdraw);
    XftFontClose( dpy, xftfont);

    XCloseDisplay(dpy);

    puts( "Closed.");
    return 0;
}