* Input/Mouse.cs:

* Platform/X11/X11Mouse.cs:
* Platform/X11/XI2Mouse.cs: Added internal list of mouse devices in
  preparation for multi-mouse support.

Source/OpenTK/Input/Mouse.cs

@@ -61,6 +61,8 @@ namespace OpenTK.Input
         /// <returns>A <see cref="OpenTK.Input.MouseState"/> structure containing the state of the mouse device.</returns>
         public static MouseState GetState(int index)
         {
+            if (index < 0)
+                throw new ArgumentOutOfRangeException("index");
             return driver.GetState(index);
         }
 

Source/OpenTK/Platform/X11/X11Mouse.cs

@@ -77,13 +77,12 @@ namespace OpenTK.Platform.X11
 
         public MouseState GetState(int index)
         {
-
-            // X11Mouse supports a single mouse only
-            if (index < 0 || index > 1)
-                throw new ArgumentOutOfRangeException("index");
-
             ProcessEvents();
-            return mouse;
+            // X11Mouse supports only one device
+            if (index == 0)
+                return mouse;
+            else
+                return new MouseState();
         }
 
         void WriteBit(MouseButton offset, int enabled)

Source/OpenTK/Platform/X11/XI2Mouse.cs

@@ -37,8 +37,10 @@ namespace OpenTK.Platform.X11
     // This should be easy: just read the device id and route the data to the correct device.
     sealed class XI2Mouse : IMouseDriver
     {
-        MouseState state = new MouseState();
+        List<MouseState> mice = new List<MouseState>();
-        X11WindowInfo window;
+        Dictionary<int, int> rawids = new Dictionary<int, int>(); // maps raw ids to mouse ids
+        int first_mouse;
+        readonly X11WindowInfo window;
         readonly int XIOpCode;
 
         static readonly Functions.EventPredicate PredicateImpl = IsEventValid;
@@ -88,13 +90,19 @@ namespace OpenTK.Platform.X11
         public MouseState GetState()
         {
             ProcessEvents();
-            return state;
+            if (mice.Count > 0)
+                return mice[0];
+            else
+                return new MouseState();
         }
 
         public MouseState GetState(int index)
         {
             ProcessEvents();
-            return state;
+            if (mice.Count > index)
+                return mice[index];
+            else
+                return new MouseState();
         }
 
         void ProcessEvents()
@@ -114,7 +122,14 @@ namespace OpenTK.Platform.X11
                     {
                         XIRawEvent raw = (XIRawEvent)
                             Marshal.PtrToStructure(cookie.data, typeof(XIRawEvent));
-        
+
+                        if (!rawids.ContainsKey(raw.deviceid))
+                        {
+                            mice.Add(new MouseState());
+                            rawids.Add(raw.deviceid, mice.Count - 1);
+                        }
+                        MouseState state = mice[rawids[raw.deviceid]];
+
                         switch (raw.evtype)
                         {
                             case XIEventType.RawMotion:
@@ -162,6 +177,7 @@ namespace OpenTK.Platform.X11
                                 }
                                 break;
                         }
+                        mice[rawids[raw.deviceid]] = state;
                     }
                     Functions.XFreeEventData(window.Display, ref cookie);
                 }