deadbeef plugin written in D broken sample

plugin.d

/*
    Example misc plugin for the DeaDBeeF audio player
    written using the D programming language

    Copyright (C) 2017 Nicolai Syvertsen <saivert@gmail.com>
    
    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.
*/
import core.runtime;
import deadbeef.api;
import deadbeef.gtkui;
import gtk.MessageDialog;
import gtkc.glib;
import headerbarui;
import std.stdio;
import std.string;
import std.experimental.logger;

static DB_functions_t *deadbeefapi;

HeaderbarUI ui;

struct Flags {
    bool disable;
    bool embed_menubar;
    bool show_seek_bar;
    bool seekbar_minimized;
    bool hide_seekbar_on_streaming;
    bool combined_playpause;
    bool show_preferences_button;
    int button_spacing;
}

Flags headerbarui_flags;
bool headerbar_stoptimer;
uint headerbar_timer;

void
printmsg(string a) {
    deadbeefapi.log("some-dlang-plugin: %s\n", a.toStringz());
}

void
headerbarui_getconfig()
{
    trace("");
    headerbarui_flags.disable = !!deadbeefapi.conf_get_int ("headerbarui.disable", 0);
    headerbarui_flags.embed_menubar = !!deadbeefapi.conf_get_int ("headerbarui.embed_menubar", 0);
    headerbarui_flags.show_seek_bar = !!deadbeefapi.conf_get_int ("headerbarui.show_seek_bar", 1);
    if (headerbarui_flags.show_seek_bar)
        headerbarui_flags.hide_seekbar_on_streaming = !!deadbeefapi.conf_get_int ("headerbarui.hide_seekbar_on_streaming", 0);
    else
        headerbarui_flags.hide_seekbar_on_streaming = false;
    headerbarui_flags.combined_playpause = !!deadbeefapi.conf_get_int ("headerbarui.combined_playpause", 1);
    headerbarui_flags.show_preferences_button = !!deadbeefapi.conf_get_int ("headerbarui.show_preferences_button", 0);
    headerbarui_flags.button_spacing = !!deadbeefapi.conf_get_int ("headerbarui.button_spacing", 6);
}

int
gtkui_get_gui_refresh_rate () {
    int fps = deadbeefapi.conf_get_int ("gtkui.refresh_rate", 10);
    if (fps < 1) {
        fps = 1;
    }
    else if (fps > 30) {
        fps = 30;
    }
    return fps;
}

extern (C) {

int
plugin_connect() {
    trace("");
    return 0;
}

int
headerbarui_update_seekbar_cb(void* userdata) {

    return cast(int)headerbar_stoptimer;
}

int
headerbarui_message (uint id, ulong ctx, uint p1, uint p2) {
    trace();
    printmsg("message");
    if (id != DB_EV_CONFIGCHANGED && headerbarui_flags.disable) return 0;
    switch (id) {
    case DB_EV_SONGSTARTED:
        headerbar_stoptimer = false;
        headerbar_timer = g_timeout_add (1000/gtkui_get_gui_refresh_rate (), &headerbarui_update_seekbar_cb, null);
        break;
    case DB_EV_SONGFINISHED:
        headerbar_stoptimer = true;
        break;
    case DB_EV_CONFIGCHANGED:
        //headerbarui_getconfig();
        //g_idle_add (headerbarui_configchanged_cb, NULL);
        //g_idle_add (headerbarui_volume_changed, NULL);
        break;
    case DB_EV_VOLUMECHANGED:
        //g_idle_add (headerbarui_volume_changed, NULL);
        break;
    default: break;
    }
    return 0;
}


int action1_callback(DB_plugin_action_s* action, int ctx) {
    printmsg ("action called");
    return 0;
}

static DB_plugin_action_s action1 = {
    flags: DB_ACTION_COMMON,
    title: "Some test action",
    name: "suckyaction",
    callback2: &action1_callback
};

static DB_misc_t plugin;


DB_plugin_t *
libdpluginsample_load (DB_functions_t *api) {
    Runtime.initialize();
    deadbeefapi = api;

    with (plugin.plugin) {
        type = DB_PLUGIN_MISC;
        api_vmajor = 1;
        api_vminor = 10;
        version_major = 1;
        version_minor = 0;
        id = "some-dlang-plugin";
        name = "D is best";
        descr = "A plugin written in D";
        copyright = "";
        website = "http://saivert.com";
        connect = &plugin_connect;
        get_actions = function DB_plugin_action_s *(DB_playItem_t* it) {
            return &action1;
        };
        stop = function int() {
            Runtime.terminate();
            return 0;
        };
        message = &headerbarui_message;
    }
    return cast(DB_plugin_t*)&plugin;
}

}