/*
 * _NET_WM_ICON helpers for slide puzzle game
 * Copyright © 2022 Nick Bowler
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

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

#if !X_DISPLAY_MISSING
#  include <X11/Intrinsic.h>
#  include <X11/Xatom.h>
#endif

#include "ewmhicon.h"
#include "colour.h"
#include "icon.h"

enum { ICON_16x16, ICON_24x24, ICON_32x32, ICON_48x48, ICON_MAX };

/*
 * Allocate storage for the EWMH _NET_WM_ICON array.  The sizes array is
 * populated with pointers to the beginning of each icon's pixel data.  For
 * example, sizes[ICON_24x24] points to the first pixel of the 24x24 image.
 *
 * The returned value can then be passed to XChangeProperty to set the icon,
 * (use EWMH_ICON_NELEM for the number of elements) and must be freed by the
 * caller.
 */
static void *ewmh_icon_alloc(unsigned long **sizes)
{
	unsigned long *buf;

	buf = calloc(sizeof *buf, EWMH_ICON_NELEM);
	if (buf) {
		sizes[ICON_16x16] = buf;
		*sizes[ICON_16x16]++ = 16;
		*sizes[ICON_16x16]++ = 16;

		sizes[ICON_24x24] = sizes[ICON_16x16] + 16*16;
		*sizes[ICON_24x24]++ = 24;
		*sizes[ICON_24x24]++ = 24;

		sizes[ICON_32x32] = sizes[ICON_24x24] + 24*24;
		*sizes[ICON_32x32]++ = 32;
		*sizes[ICON_32x32]++ = 32;

		sizes[ICON_48x48] = sizes[ICON_32x32] + 32*32;
		*sizes[ICON_48x48]++ = 48;
		*sizes[ICON_48x48]++ = 48;
	}

	return buf;
}

static unsigned long scale16to8(unsigned x)
{
	return x*0xfful / 0xffff;
}

static unsigned long wm_pixel(const XColor *c)
{
	return 0xff000000
	     | scale16to8(c->red) << 16
	     | scale16to8(c->green) << 8
	     | scale16to8(c->blue);
}

static void do_remap(void *icon, unsigned size, const XColor *map)
{
	unsigned char *index = icon;
	unsigned long *argb = icon;
	unsigned i, count = size*size;

	for (i = 0; i < count; i++) {
		argb[count-i-1] = wm_pixel(map + index[count-i-1]);
	}
}

void *ewmh_icon_generate(const unsigned long *seq, const XColor *map)
{
	unsigned long *buf, *sizes[ICON_MAX];
	unsigned i, j;

	buf = ewmh_icon_alloc(sizes);
	if (!buf)
		return NULL;

	for (i = 0; i < 9; i++) {
		unsigned x = i%3, y = i/3;

		icon_tile16((void *)sizes[ICON_16x16], seq[i], x, y);
		icon_tile24((void *)sizes[ICON_24x24], seq[i], x, y);
		icon_tile32((void *)sizes[ICON_32x32], seq[i], x, y);
		icon_tile48((void *)sizes[ICON_48x48], seq[i], x, y);
	}

	for (i = 0; i < ICON_MAX; i++) {
		/* Produces the sequence 16, 24, 32, 48 */
		unsigned size = 16 + (1u<<i)/2 * 8;

		do_remap(sizes[i], size, map);
	}

	return buf;
}

#if !X_DISPLAY_MISSING

/*
 * EWMH-supporting window managers that handle _NET_WM_ICON add this atom to
 * the _NET_SUPPORTED list on the root window.  Look for that and return 1
 * if it is found, or 0 otherwise.
 */
int ewmh_probe_wm_icon(Widget shell)
{
	Display *display = XtDisplay(shell);
	Screen *screen = XtScreen(shell);
	Window root = RootWindowOfScreen(screen);
	Atom net_supported, net_wm_icon, type;

	unsigned long offset = 0, i, nitems, bytes_after, *props;
	unsigned char *prop_return;
	int format;

	net_wm_icon = XInternAtom(display, "_NET_WM_ICON", 0);
	net_supported = XInternAtom(display, "_NET_SUPPORTED", 0);
	do {
		XGetWindowProperty(display, root, net_supported, offset, 10,
		                            0, XA_ATOM, &type, &format,
		                            &nitems, &bytes_after,
		                            &prop_return);

		if (format != 32 || type != XA_ATOM)
			break;
		offset += nitems;

		props = (void *)prop_return;
		for (i = 0; i < nitems; i++) {
			if (props[i] == net_wm_icon) {
				XFree(props);
				return 1;
			}
		}
		XFree(props);
	} while (nitems > 0 && bytes_after > 0);

	return 0;
}

#endif