Move cursor visible check into implementations

src/OpenTK/NativeWindow.cs

@@ -476,11 +476,7 @@ namespace OpenTK
         public bool CursorVisible
         {
             get { return implementation.CursorVisible; }
-            set
+            set { implementation.CursorVisible = value; }
-            {
-                if (value == implementation.CursorVisible) return;
-                implementation.CursorVisible = value;
-            }
         }
 
         /// <summary>

src/OpenTK/Platform/Linux/LinuxNativeWindow.cs

@@ -508,6 +508,7 @@ namespace OpenTK.Platform.Linux
             }
             set
             {
+                if (value == is_cursor_visible) return;
                 if (value && !is_cursor_visible)
                 {
                     SetCursor(cursor_current);

src/OpenTK/Platform/MacOS/CocoaNativeWindow.cs

@@ -1239,6 +1239,7 @@ namespace OpenTK.Platform.MacOS
             get { return cursorVisible; }
             set
             {
+                if (value == cursorVisible) return;
                 if (value && !cursorVisible)
                 {
                     SetCursorVisible(true);

src/OpenTK/Platform/SDL2/Sdl2NativeWindow.cs

@@ -933,6 +933,7 @@ namespace OpenTK.Platform.SDL2
             }
             set
             {
+                if (value == is_cursor_visible) return;
                 lock (sync)
                 {
                     if (Exists)