QuickLook/QuickLook/FocusMonitor.cs

// Copyright © 2017 Paddy Xu
// 
// This file is part of QuickLook program.
// 
// 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 <http://www.gnu.org/licenses/>.

using System;
using System.Threading;
using System.Threading.Tasks;

namespace QuickLook
{
    internal class FocusMonitor
    {
        public delegate void HeartbeatEventHandler(HeartbeatEventArgs e);

        private static FocusMonitor _instance;

        public bool IsRunning { get; private set; }

        public event HeartbeatEventHandler Heartbeat;

        public void Start()
        {
            IsRunning = true;

            new Task(() =>
            {
                while (IsRunning)
                {
                    Thread.Sleep(500);

                    if (NativeMethods.QuickLook.GetFocusedWindowType() ==
                        NativeMethods.QuickLook.FocusedWindowType.Invalid)
                        continue;

                    var file = NativeMethods.QuickLook.GetCurrentSelection();
                    Heartbeat?.Invoke(new HeartbeatEventArgs(DateTime.Now.Ticks, file));
                }
            }).Start();
        }

        public void Stop()
        {
            IsRunning = false;
        }

        internal static FocusMonitor GetInstance()
        {
            return _instance ?? (_instance = new FocusMonitor());
        }
    }

    internal class HeartbeatEventArgs : EventArgs
    {
        public HeartbeatEventArgs(long tick, string files)
        {
            InvokeTick = tick;
            FocusedFile = files;
        }

        public long InvokeTick { get; }
        public string FocusedFile { get; }
    }
}