Provide support of HotKeys to manage thumbnails and corresponding EVE clients - implemented w/o GUI required to set hotkeys

Eve-O-Preview/Hotkeys/HotkeyHandler.cs

@@ -0,0 +1,159 @@
+using System;
+using System.Windows.Forms;
+using System.ComponentModel;
+
+namespace EveOPreview.UI
+{
+	class HotkeyHandler : IMessageFilter, IDisposable
+	{
+		private static int _currentId;
+		private const int MaxId = 0xBFFF;
+
+		#region Private fields
+		private readonly int _hotkeyId;
+		private readonly IntPtr _hotkeyTarget;
+		#endregion
+
+		public HotkeyHandler(IntPtr target, Keys hotkey)
+		{
+			this._hotkeyId = HotkeyHandler._currentId;
+			HotkeyHandler._currentId = (HotkeyHandler._currentId + 1) & HotkeyHandler.MaxId;
+
+			this._hotkeyTarget = target;
+
+			// Assign properties
+			this.IsRegistered = false;
+
+			this.KeyCode = hotkey;
+		}
+
+		public void Dispose()
+		{
+			if (this.IsRegistered)
+			{
+				this.Unregister();
+			}
+
+			GC.SuppressFinalize(this);
+		}
+
+		~HotkeyHandler()
+		{
+			// Unregister the hotkey if necessary
+			if (this.IsRegistered)
+			{
+				try
+				{
+					this.Unregister();
+				}
+				catch (Exception)
+				{
+					// Please no exceptions in the finalizer thread
+				}
+			}
+		}
+
+		public bool IsRegistered { get; private set; }
+
+		public Keys KeyCode { get; private set; }
+
+		public event HandledEventHandler Pressed;
+
+		public bool CanRegister()
+		{
+			// Any exception means "no, you can't register"
+			try
+			{
+				// Attempt to register
+				if (this.Register())
+				{
+					// Unregister and say we managed it
+					this.Unregister();
+					return true;
+				}
+			}
+			catch (Win32Exception)
+			{
+			}
+			catch (NotSupportedException)
+			{
+			}
+
+			return false;
+		}
+
+		public bool Register()
+		{
+			// Check that we have not registered
+			if (this.IsRegistered)
+			{
+				throw new NotSupportedException("This hotkey is already registered");
+			}
+
+			if (this.KeyCode == Keys.None)
+			{
+				throw new NotSupportedException("Cannot register an empty hotkey");
+			}
+
+			// Remove all modifiers from the 'main' hotkey
+			uint key = (uint)this.KeyCode & (~(uint)Keys.Alt) & (~(uint)Keys.Control) & (~(uint)Keys.Shift);
+
+			// Get unmanaged version of the modifiers code
+			uint modifiers = (this.KeyCode.HasFlag(Keys.Alt) ? HotkeyHandlerNativeMethods.MOD_ALT : 0)
+							 | (this.KeyCode.HasFlag(Keys.Control) ? HotkeyHandlerNativeMethods.MOD_CONTROL : 0)
+							 | (this.KeyCode.HasFlag(Keys.Shift) ? HotkeyHandlerNativeMethods.MOD_SHIFT : 0);
+
+			// Register the hotkey
+			if (!HotkeyHandlerNativeMethods.RegisterHotKey(this._hotkeyTarget, this._hotkeyId, modifiers, key))
+			{
+				return false;
+			}
+
+			Application.AddMessageFilter(this);
+
+			this.IsRegistered = true;
+
+			// We successfully registered
+			return true;
+		}
+
+		public void Unregister()
+		{
+			// Check that we have registered
+			if (!this.IsRegistered)
+			{
+				throw new NotSupportedException("This hotkey was not registered");
+			}
+
+			Application.RemoveMessageFilter(this);
+
+			// Clean up after ourselves
+			if (!HotkeyHandlerNativeMethods.UnregisterHotKey(this._hotkeyTarget, this._hotkeyId))
+			{
+				throw new Win32Exception();
+			}
+
+			this.IsRegistered = false;
+		}
+
+		#region IMessageFilter
+		public bool PreFilterMessage(ref Message message)
+		{
+			return this.IsRegistered
+					&& (message.Msg == HotkeyHandlerNativeMethods.WM_HOTKEY)
+					&& (message.WParam.ToInt32() == this._hotkeyId)
+					&& this.OnPressed();
+		}
+		#endregion
+
+		private bool OnPressed()
+		{
+			// Fire the event if we can
+			HandledEventArgs handledEventArgs = new HandledEventArgs(false);
+			this.Pressed?.Invoke(this, handledEventArgs);
+
+			// Return whether we handled the event or not
+			return handledEventArgs.Handled;
+		}
+	}
+}