tray_icon.c

/*
 * A simple client icon that "does nothing".
 *
 * Copyright © 2021 Uli Schlachter <psychon@znc.in>
 *
 * 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 2 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, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <xcb/xcb.h>
#include <xcb/xcb_atom.h>
#include <xcb/xcb_aux.h>

#include "common/atoms.h"
#include "common/util.h"

// Include all the C code we might need directly into this file - I am lazy
#include "common/atoms.c"
#include "common/util.c"

#define SYSTEM_TRAY_REQUEST_DOCK 0

static xcb_atom_t systray_atom(xcb_connection_t *conn, int screen) {
    char *atom_name;
    xcb_intern_atom_reply_t *reply;
    xcb_atom_t atom;

    atom_name = xcb_atom_name_by_screen("_NET_SYSTEM_TRAY", screen);
    if(!atom_name)
        fatal("Error getting systray atom name\n");

    reply = xcb_intern_atom_reply(conn, xcb_intern_atom(conn, 0, strlen(atom_name), atom_name), NULL);
    free(atom_name);
    if (!reply)
        fatal("Error interning systray icon\n");

    atom = reply->atom;
    free(reply);
    return atom;
}

static xcb_window_t find_systray(xcb_connection_t *conn, xcb_atom_t net_system_tray) {
    xcb_get_selection_owner_reply_t* reply = xcb_get_selection_owner_reply(conn, xcb_get_selection_owner(conn, net_system_tray), NULL);
    if (!reply)
        fatal("Failed to request selection owner\n");
    xcb_window_t owner = reply->owner;
    if (owner == XCB_NONE)
        fatal("No systray running\n");
    free(reply);
    return owner;
}

static uint32_t get_color(xcb_connection_t *conn, xcb_screen_t *screen, uint16_t red, uint16_t green, uint16_t blue) {
    xcb_alloc_color_reply_t *reply = xcb_alloc_color_reply(conn, xcb_alloc_color(conn, screen->default_colormap, red, green, blue), NULL);
    if (!reply)
        fatal("Error allocating color");
    uint32_t pixel = reply->pixel;
    free(reply);
    return pixel;
}

int main() {
    int default_screen;
    xcb_connection_t* conn = xcb_connect(NULL, &default_screen);
    if (xcb_connection_has_error(conn)) {
        fatal("Could not connect to X11 server: %d\n", xcb_connection_has_error(conn));
    }
    atoms_init(conn);
    xcb_screen_t* screen = xcb_aux_get_screen(conn, default_screen);

    // Create a window for the systray icon
    xcb_window_t window = xcb_generate_id(conn);
    xcb_create_window(conn, screen->root_depth, window, screen->root, 0, 0, 10, 10, 0, XCB_WINDOW_CLASS_INPUT_OUTPUT,
            screen->root_visual, XCB_CW_BACK_PIXEL, (uint32_t[]) { get_color(conn, screen, 0xffff, 0x9999, 0x0000) });
    xcb_change_property(conn, XCB_PROP_MODE_REPLACE, window, _XEMBED_INFO, _XEMBED_INFO, 32, 2, (uint32_t[]) { 0, 1 });

    // Make our window a systray icon
    xcb_window_t systray_owner = find_systray(conn, systray_atom(conn, default_screen));
    xcb_client_message_event_t ev;

    p_clear(&ev, 1);
    ev.response_type = XCB_CLIENT_MESSAGE;
    ev.window = systray_owner;
    ev.format = 32;
    ev.data.data32[0] = XCB_CURRENT_TIME;
    ev.data.data32[1] = SYSTEM_TRAY_REQUEST_DOCK;
    ev.data.data32[2] = window;
    ev.data.data32[3] = 0;
    ev.data.data32[4] = 0;
    ev.type = _NET_SYSTEM_TRAY_OPCODE;
    xcb_send_event(conn, false, systray_owner, XCB_EVENT_MASK_NO_EVENT, (char *) &ev);

    xcb_flush(conn);
    xcb_generic_event_t *event;
    while ((event = xcb_wait_for_event(conn)) != NULL) {
        free(event);
    }

    xcb_disconnect(conn);
    return 0;
}

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