/*
 * _NET_WM_ICON helpers for slide puzzle game
 * Copyright © 2022-2023 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>
#include <stdint.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 };

static unsigned long scale16to8(uint_least32_t x)
{
	return x*0xff / 0xffff;
}

static unsigned long wm_pixel(const XColor *c)
{
	uint_least32_t t = -1;

	t = (t << 8) + scale16to8(c->red);
	t = (t << 8) + scale16to8(c->green);
	t = (t << 8) + scale16to8(c->blue);

	return t & 0xffffffff;
}

void ewmh_icon_prepare_cmap(XColor *map, unsigned n)
{
	unsigned i;

	for (i = 0; i < n; i++) {
		map[i].pixel = wm_pixel(&map[i]);
	}
}

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

	area--;
	for (i = 0; i <= area; i++) {
		argb[area-i] = (map + index[area-i])->pixel;
	}
}

void *ewmh_icon_generate(const unsigned long *seq, const XColor *map)
{
	static const unsigned char dims[ICON_MAX] = { 16, 24, 32, 48 };
	unsigned long *work, *ret;
	unsigned i, j, fullsize, size;

	work = ret = malloc(sizeof *work * EWMH_ICON_NELEM);
	if (!work)
		return NULL;

	for (i = fullsize = 0; i < ICON_MAX; i++) {
		work += fullsize;

		size = dims[i];
		*work++ = size;
		*work++ = size;

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

			switch (i) {
			case 0: icon_tile16((void *)work, seq[j], x, y); break;
			case 1: icon_tile24((void *)work, seq[j], x, y); break;
			case 2: icon_tile32((void *)work, seq[j], x, y); break;
			case 3: icon_tile48((void *)work, seq[j], x, y); break;
			}
		}

		fullsize = size*size;
		do_remap(work, fullsize, map);
	}

	return ret;
}

#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