Add SteamController implementation

This adds a Steam Shortcuts, Desktop Mode, and X360 Emulation
- Supports all Steam Shortcuts (including on-screen keyboard, and brightness)
- Supports Desktop mode (with a scroll on left pad and left stick), and trackpoint (on right stick)
- Supports X360 mode: hold Options for 1s to switch between Desktop and X360
- Holding Steam button enables Desktop like controls and stops passing all inputs to X360

SteamController/Devices/KeyboardController.cs

@@ -0,0 +1,95 @@
+using WindowsInput;
+
+namespace SteamController.Devices
+{
+    public class KeyboardController : IDisposable
+    {
+        InputSimulator simulator = new InputSimulator();
+
+        HashSet<VirtualKeyCode> keyCodes = new HashSet<VirtualKeyCode>();
+        HashSet<VirtualKeyCode> lastKeyCodes = new HashSet<VirtualKeyCode>();
+
+        public KeyboardController()
+        {
+        }
+
+        public void Dispose()
+        {
+        }
+
+        public bool this[VirtualKeyCode button]
+        {
+            get { return keyCodes.Contains(button); }
+            set
+            {
+                if (value)
+                    keyCodes.Add(button);
+                else
+                    keyCodes.Remove(button);
+            }
+        }
+
+        public VirtualKeyCode[] DownKeys
+        {
+            get { return keyCodes.ToArray(); }
+        }
+
+        internal void BeforeUpdate()
+        {
+            lastKeyCodes = keyCodes;
+            keyCodes = new HashSet<VirtualKeyCode>();
+        }
+
+        internal void Update()
+        {
+            try
+            {
+                // Key Up: it is missing now
+                var keyUp = lastKeyCodes.Except(keyCodes).ToArray();
+                if (keyUp.Any())
+                    simulator.Keyboard.KeyUp(keyUp);
+
+                // Key Down: new keys being down
+                var keyDown = keyCodes.Except(lastKeyCodes).ToArray();
+                if (keyDown.Any())
+                    simulator.Keyboard.KeyUp(keyDown);
+            }
+            catch (InvalidOperationException)
+            {
+            }
+        }
+
+        public void KeyPress(params VirtualKeyCode[] keyCodes)
+        {
+            try
+            {
+                simulator.Keyboard.KeyPress(keyCodes);
+            }
+            catch (InvalidOperationException)
+            {
+            }
+        }
+
+        public void KeyPress(VirtualKeyCode modifierKey, params VirtualKeyCode[] keyCodes)
+        {
+            try
+            {
+                simulator.Keyboard.ModifiedKeyStroke(modifierKey, keyCodes);
+            }
+            catch (InvalidOperationException)
+            {
+            }
+        }
+
+        public void KeyPress(IEnumerable<VirtualKeyCode> modifierKeys, params VirtualKeyCode[] keyCodes)
+        {
+            try
+            {
+                simulator.Keyboard.ModifiedKeyStroke(modifierKeys, keyCodes);
+            }
+            catch (InvalidOperationException)
+            {
+            }
+        }
+    }
+}