QuickLook/QuickLook/KeystrokeDispatcher.cs

// Copyright © 2017-2025 QL-Win Contributors
//
// 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 QuickLook.Common.Helpers;
using QuickLook.Helpers;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Windows.Forms;

namespace QuickLook;

internal class KeystrokeDispatcher : IDisposable
{
    private static KeystrokeDispatcher _instance;

    private static HashSet<Keys> _validKeys;

    private GlobalKeyboardHook _hook;
    private bool _isPreviewRequest;
    private bool _spaceIsDown;
    private long _spaceHoldTick;
    private long _lastInvalidKeyPressTick;

    private const long HOLD_TO_PREVIEW_DURATION = TimeSpan.TicksPerMillisecond * 750;
    private const long VALID_KEY_PRESS_DELAY = TimeSpan.TicksPerSecond * 1;

    protected KeystrokeDispatcher()
    {
        InstallKeyHook(KeyDownEventHandler, KeyUpEventHandler);

        _validKeys =
        [
            Keys.Up, Keys.Down, Keys.Left, Keys.Right,
            Keys.Enter, Keys.Space, Keys.Escape
        ];
    }

    public void Dispose()
    {
        _hook?.Dispose();
        _hook = null;
    }

    private void KeyDownEventHandler(object sender, KeyEventArgs e)
    {
        CallViewWindowManagerInvokeRoutine(e, true);
    }

    private void KeyUpEventHandler(object sender, KeyEventArgs e)
    {
        CallViewWindowManagerInvokeRoutine(e, false);
    }

    private void CallViewWindowManagerInvokeRoutine(KeyEventArgs e, bool isKeyDown)
    {
        // skip invalid keys, but record the timestamp
        if (!_validKeys.Contains(e.KeyCode))
        {
            Debug.WriteLine($"Invalid keypress: key={e.KeyCode},down={isKeyDown}, time={_lastInvalidKeyPressTick}");
            _lastInvalidKeyPressTick = DateTime.Now.Ticks;
            return;
        }

        // skip valid keys when modifiers are used
        if (isKeyDown && e.Modifiers != Keys.None)
            return;

        // skip if key is valid but too close after pressing an invalid key
        if (DateTime.Now.Ticks - _lastInvalidKeyPressTick < VALID_KEY_PRESS_DELAY)
            return;
        _lastInvalidKeyPressTick = 0L;

        // skip if user is holding Space (don't skip other valid keys)
        if (isKeyDown && e.KeyCode == Keys.Space)
        {
            if (_spaceIsDown)
                return;
            _spaceIsDown = true;
            _spaceHoldTick = DateTime.Now.Ticks;
        }

        // check if the valid key is a preview request
        if (isKeyDown)
        {
            _isPreviewRequest = NativeMethods.QuickLook.GetFocusedWindowType() !=
                                NativeMethods.QuickLook.FocusedWindowType.Invalid;
            _isPreviewRequest |= WindowHelper.IsForegroundWindowBelongToSelf();
        } // else (when isKeyDown is false), _isPreviewRequest retain its current state

        // call InvokeRoutine only when user pressed a key in a valid window, or
        // released a key which was pressed in a valid window, with an exception of Space which
        // must be hold for 750ms before releasing.
        if (_isPreviewRequest)
        {
            if (isKeyDown || e.KeyCode != Keys.Space ||
                DateTime.Now.Ticks - _spaceHoldTick >= HOLD_TO_PREVIEW_DURATION)
                InvokeRoutine(e.KeyCode, isKeyDown);
        }

        // when the key has been released, reset variables
        if (!isKeyDown)
        {
            _isPreviewRequest = false;
            _spaceIsDown = e.KeyCode != Keys.Space && _spaceIsDown;
        }
    }

    private void InvokeRoutine(Keys key, bool isKeyDown)
    {
        Debug.WriteLine($"InvokeRoutine: key={key},down={isKeyDown}");

        if (isKeyDown)
        {
            switch (key)
            {
                case Keys.Enter:
                    PipeServerManager.SendMessage(PipeMessages.RunAndClose);
                    break;

                case Keys.Space:
                    PipeServerManager.SendMessage(PipeMessages.Toggle);
                    break;
            }
        }
        else
        {
            switch (key)
            {
                case Keys.Up:
                case Keys.Down:
                case Keys.Left:
                case Keys.Right:
                    PipeServerManager.SendMessage(PipeMessages.Switch);
                    break;

                case Keys.Escape:
                    PipeServerManager.SendMessage(PipeMessages.Close);
                    break;

                case Keys.Space:
                    PipeServerManager.SendMessage(PipeMessages.Toggle);
                    break;
            }
        }
    }

    private void InstallKeyHook(KeyEventHandler downHandler, KeyEventHandler upHandler)
    {
        _hook = GlobalKeyboardHook.GetInstance();

        _hook.KeyDown += downHandler;
        _hook.KeyUp += upHandler;
    }

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