awesome/objects/selection_watcher.c

/*
 * selection_watcher.h - selection change watcher
 *
 * Copyright © 2019 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 "objects/selection_watcher.h"
#include "common/luaobject.h"
#include "globalconf.h"

#include <xcb/xfixes.h>

#define REGISTRY_WATCHER_TABLE_INDEX "awesome_selection_watchers"

typedef struct selection_watcher_t
{
    LUA_OBJECT_HEADER
    /** Is this watcher currently active and watching? Used as reference with luaL_ref */
    int active_ref;
    /** Atom identifying the selection to watch */
    xcb_atom_t selection;
    /** Window used for watching */
    xcb_window_t window;
} selection_watcher_t;

static lua_class_t selection_watcher_class;
LUA_OBJECT_FUNCS(selection_watcher_class, selection_watcher_t, selection_watcher)

void
event_handle_xfixes_selection_notify(xcb_generic_event_t *ev)
{
    xcb_xfixes_selection_notify_event_t *e = (void *) ev;
    lua_State *L = globalconf_get_lua_State();

    /* Iterate over all active selection watchers */
    lua_pushliteral(L, REGISTRY_WATCHER_TABLE_INDEX);
    lua_rawget(L, LUA_REGISTRYINDEX);
    lua_pushnil(L);
    while (lua_next(L, -2) != 0) {
        if (lua_type(L, -1) == LUA_TUSERDATA) {
            selection_watcher_t *selection = lua_touserdata(L, -1);

            if (selection->selection == e->selection && selection->window == e->window) {
                lua_pushboolean(L, e->owner != XCB_NONE);
                luaA_object_emit_signal(L, -2, "selection_changed", 1);
            }
        }
        /* Remove the watcher */
        lua_pop(L, 1);
    }
    /* Remove watcher table */
    lua_pop(L, 1);
}

/** Create a new selection watcher object.
 * \param L The Lua VM state.
 * \return The number of elements pushed on the stack.
 */
static int
luaA_selection_watcher_new(lua_State *L)
{
    size_t name_length;
    const char *name;
    xcb_intern_atom_reply_t *reply;
    selection_watcher_t *selection;

    name = luaL_checklstring(L, 2, &name_length);
    selection = (void *) selection_watcher_class.allocator(L);
    selection->active_ref = LUA_NOREF;
    selection->window = XCB_NONE;

    /* Get the atom identifying the selection to watch */
    reply = xcb_intern_atom_reply(globalconf.connection,
            xcb_intern_atom_unchecked(globalconf.connection, false, name_length, name),
            NULL);
    if (reply) {
        selection->selection = reply->atom;
        p_delete(&reply);
    }

    return 1;
}

static int
luaA_selection_watcher_set_active(lua_State *L, selection_watcher_t *selection)
{
    bool b = luaA_checkboolean(L, -1);
    bool is_active = selection->active_ref != LUA_NOREF;
    if(b != is_active)
    {
        if (b)
        {
            /* Selection becomes active */

            /* Create a window for it */
            if (selection->window == XCB_NONE)
                selection->window = xcb_generate_id(globalconf.connection);
            xcb_create_window(globalconf.connection, globalconf.screen->root_depth,
                    selection->window, globalconf.screen->root, -1, -1, 1, 1, 0,
                    XCB_COPY_FROM_PARENT, globalconf.screen->root_visual,
                    0, NULL);

            /* Start watching for selection changes */
            if (globalconf.have_xfixes)
            {
                xcb_xfixes_select_selection_input(globalconf.connection, selection->window, selection->selection,
                        XCB_XFIXES_SELECTION_EVENT_MASK_SET_SELECTION_OWNER |
                        XCB_XFIXES_SELECTION_EVENT_MASK_SELECTION_WINDOW_DESTROY |
                        XCB_XFIXES_SELECTION_EVENT_MASK_SELECTION_CLIENT_CLOSE);
            } else {
                luaA_warn(L, "X11 server does not support the XFixes extension; cannot watch selections");
            }

            /* Reference the selection watcher. For this, first get the tracking
             * table out of the registry. */
            lua_pushliteral(L, REGISTRY_WATCHER_TABLE_INDEX);
            lua_rawget(L, LUA_REGISTRYINDEX);

            /* Then actually get the reference */
            lua_pushvalue(L, -3 - 1);
            selection->active_ref = luaL_ref(L, -2);

            /* And pop the tracking table again */
            lua_pop(L, 1);
        } else {
            /* Stop watching and destroy the window */
            if (globalconf.have_xfixes)
                xcb_xfixes_select_selection_input(globalconf.connection, selection->window, selection->selection, 0);
            xcb_destroy_window(globalconf.connection, selection->window);

            /* Unreference the selection object */
            lua_pushliteral(L, REGISTRY_WATCHER_TABLE_INDEX);
            lua_rawget(L, LUA_REGISTRYINDEX);
            luaL_unref(L, -1, selection->active_ref);
            lua_pop(L, 1);

            selection->active_ref = LUA_NOREF;
        }
        luaA_object_emit_signal(L, -3, "property::active", 0);
    }
    return 0;
}

static int
luaA_selection_watcher_get_active(lua_State *L, selection_watcher_t *selection)
{
    lua_pushboolean(L, selection->active_ref != LUA_NOREF);
    return 1;
}

void
selection_watcher_class_setup(lua_State *L)
{
    static const struct luaL_Reg selection_watcher_methods[] =
    {
        LUA_CLASS_METHODS(selection_watcher)
        { "__call", luaA_selection_watcher_new },
        { NULL, NULL }
    };

    static const struct luaL_Reg selection_watcher_meta[] = {
        LUA_OBJECT_META(selection_watcher)
        LUA_CLASS_META
        { NULL, NULL }
    };

    /* Reference a table in the registry that tracks active watchers. This code
     * does debug.getregistry()[REGISTRY_WATCHER_TABLE_INDEX] = {}
     */
    lua_pushliteral(L, REGISTRY_WATCHER_TABLE_INDEX);
    lua_newtable(L);
    lua_rawset(L, LUA_REGISTRYINDEX);

    luaA_class_setup(L, &selection_watcher_class, "selection_watcher", NULL,
            (lua_class_allocator_t) selection_watcher_new, NULL, NULL,
            luaA_class_index_miss_property, luaA_class_newindex_miss_property,
            selection_watcher_methods, selection_watcher_meta);
    luaA_class_add_property(&selection_watcher_class, "active",
            (lua_class_propfunc_t) luaA_selection_watcher_set_active,
            (lua_class_propfunc_t) luaA_selection_watcher_get_active,
            (lua_class_propfunc_t) luaA_selection_watcher_set_active);
}

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