Fix #715: add 1s timeout before any previewing request

QuickLook/App.xaml.cs

@@ -16,8 +16,6 @@
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 using System;
-using System.Configuration;
-using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Reflection;
@@ -80,7 +78,7 @@ namespace QuickLook
                 Shutdown();
                 return;
             }
-            
+
             CheckUpdate();
             RunListener(e);
 
@@ -115,7 +113,7 @@ namespace QuickLook
 
             PluginManager.GetInstance();
             ViewWindowManager.GetInstance();
-            BackgroundListener.GetInstance();
+            KeystrokeDispatcher.GetInstance();
             PipeServerManager.GetInstance();
         }
 
@@ -128,7 +126,7 @@ namespace QuickLook
 
             PipeServerManager.GetInstance().Dispose();
             TrayIconManager.GetInstance().Dispose();
-            BackgroundListener.GetInstance().Dispose();
+            KeystrokeDispatcher.GetInstance().Dispose();
             ViewWindowManager.GetInstance().Dispose();
         }
 

QuickLook/Helpers/GlobalKeyboardHook.cs

@@ -16,14 +16,13 @@
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 using System;
-using System.Collections.Generic;
 using System.Windows.Forms;
 using System.Windows.Input;
 using QuickLook.Common.NativeMethods;
 using KeyEventArgs = System.Windows.Forms.KeyEventArgs;
 using KeyEventHandler = System.Windows.Forms.KeyEventHandler;
 
-namespace QuickLook
+namespace QuickLook.Helpers
 {
     internal class GlobalKeyboardHook : IDisposable
     {
@@ -31,7 +30,6 @@ namespace QuickLook
 
         private User32.KeyboardHookProc _callback;
         private IntPtr _hhook = IntPtr.Zero;
-        internal List<Keys> HookedKeys = new List<Keys>();
 
         protected GlobalKeyboardHook()
         {
@@ -72,25 +70,23 @@ namespace QuickLook
 
         private int HookProc(int code, int wParam, ref User32.KeyboardHookStruct lParam)
         {
-            if (code >= 0)
-                if (!IsWindowsKeyPressed())
-                {
-                    var key = (Keys) lParam.vkCode;
-                    if (HookedKeys.Contains(key))
-                    {
-                        key = AddModifiers(key);
+            if (code < 0)
+                return User32.CallNextHookEx(_hhook, code, wParam, ref lParam);
 
-                        var kea = new KeyEventArgs(key);
-                        if (wParam == User32.WM_KEYDOWN || wParam == User32.WM_SYSKEYDOWN)
-                            KeyDown?.Invoke(this, kea);
-                        if (wParam == User32.WM_KEYUP || wParam == User32.WM_SYSKEYUP)
-                            KeyUp?.Invoke(this, kea);
-                        if (kea.Handled)
-                            return 1;
-                    }
-                }
+            if (IsWindowsKeyPressed())
+                return User32.CallNextHookEx(_hhook, code, wParam, ref lParam);
 
-            return User32.CallNextHookEx(_hhook, code, wParam, ref lParam);
+            var key = (Keys) lParam.vkCode;
+            key = AddModifiers(key);
+
+            var kea = new KeyEventArgs(key);
+
+            if (wParam == User32.WM_KEYDOWN || wParam == User32.WM_SYSKEYDOWN)
+                KeyDown?.Invoke(this, kea);
+            else if (wParam == User32.WM_KEYUP || wParam == User32.WM_SYSKEYUP)
+                KeyUp?.Invoke(this, kea);
+
+            return kea.Handled ? 1 : User32.CallNextHookEx(_hhook, code, wParam, ref lParam);
         }
 
         private bool IsWindowsKeyPressed()

QuickLook/KeystrokeDispatcher.cs

@@ -16,22 +16,35 @@
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.Windows.Forms;
 using QuickLook.Common.Helpers;
+using QuickLook.Helpers;
 
 namespace QuickLook
 {
-    internal class BackgroundListener : IDisposable
+    internal class KeystrokeDispatcher : IDisposable
     {
-        private static BackgroundListener _instance;
+        private static KeystrokeDispatcher _instance;
+
+        private static HashSet<Keys> _validKeys;
 
         private GlobalKeyboardHook _hook;
         private bool _isKeyDownInDesktopOrShell;
+        private long _lastInvalidKeyPressTick;
 
-        protected BackgroundListener()
+        private const long VALID_KEY_PRESS_DELAY = TimeSpan.TicksPerSecond * 1;
+
+        protected KeystrokeDispatcher()
         {
             InstallKeyHook(KeyDownEventHandler, KeyUpEventHandler);
+
+            _validKeys = new HashSet<Keys>(new[]
+            {
+                Keys.Up, Keys.Down, Keys.Left, Keys.Right,
+                Keys.Enter, Keys.Space, Keys.Escape
+            });
         }
 
         public void Dispose()
@@ -55,7 +68,7 @@ namespace QuickLook
             if (e.Modifiers != Keys.None)
                 return;
 
-            // set variable only when KeyDown
+            // check if the window is valid at the time of pressing a key, used for case 1
             if (isKeyDown)
             {
                 _isKeyDownInDesktopOrShell = NativeMethods.QuickLook.GetFocusedWindowType() !=
@@ -64,17 +77,32 @@ namespace QuickLook
                 _isKeyDownInDesktopOrShell |= WindowHelper.IsForegroundWindowBelongToSelf();
             }
 
-            // call InvokeRoutine only when the KeyDown is valid
+            // call InvokeRoutine only when:
+            // (1) user released a key which was pressed in a valid window, or
+            // (2) user pressed a key in a valid window
             if (_isKeyDownInDesktopOrShell)
                 InvokeRoutine(e.KeyCode, isKeyDown);
 
-            // reset variable only when KeyUp
+            // in case 2, reset the variable
             if (!isKeyDown)
                 _isKeyDownInDesktopOrShell = false;
         }
 
         private void InvokeRoutine(Keys key, bool isKeyDown)
         {
+            if (!_validKeys.Contains(key))
+            {
+                Debug.WriteLine($"Invalid keypress: key={key},down={isKeyDown}, time={_lastInvalidKeyPressTick}");
+
+                _lastInvalidKeyPressTick = DateTime.Now.Ticks;
+                return;
+            }
+
+            if (DateTime.Now.Ticks - _lastInvalidKeyPressTick < VALID_KEY_PRESS_DELAY)
+                return;
+
+            _lastInvalidKeyPressTick = 0L;
+
             Debug.WriteLine($"InvokeRoutine: key={key},down={isKeyDown}");
 
             if (isKeyDown)
@@ -110,20 +138,13 @@ namespace QuickLook
         {
             _hook = GlobalKeyboardHook.GetInstance();
 
-            _hook.HookedKeys.Add(Keys.Enter);
-            _hook.HookedKeys.Add(Keys.Space);
-            _hook.HookedKeys.Add(Keys.Escape);
-            _hook.HookedKeys.Add(Keys.Up);
-            _hook.HookedKeys.Add(Keys.Down);
-            _hook.HookedKeys.Add(Keys.Left);
-            _hook.HookedKeys.Add(Keys.Right);
             _hook.KeyDown += downHandler;
             _hook.KeyUp += upHandler;
         }
 
-        internal static BackgroundListener GetInstance()
+        internal static KeystrokeDispatcher GetInstance()
         {
-            return _instance ?? (_instance = new BackgroundListener());
+            return _instance ?? (_instance = new KeystrokeDispatcher());
         }
     }
 }

QuickLook/QuickLook.csproj

@@ -180,8 +180,8 @@
       <DependentUpon>App.xaml</DependentUpon>
       <SubType>Code</SubType>
     </Compile>
-    <Compile Include="BackgroundListener.cs" />
-    <Compile Include="GlobalKeyboardHook.cs" />
+    <Compile Include="KeystrokeDispatcher.cs" />
+    <Compile Include="Helpers\GlobalKeyboardHook.cs" />
     <Compile Include="ViewerWindow.xaml.cs">
       <DependentUpon>ViewerWindow.xaml</DependentUpon>
       <SubType>Code</SubType>