enforce single use of HID submodule

Author: facchinm

libraries/Keyboard/Keyboard.h

@@ -19,7 +19,13 @@
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
-#if 1
+#if defined(_USING_HID)
+
+#error "Can only attach one submodule to HID module"
+
+#else
+
+#define _USING_HID
 
 #include "HID.h"
 

libraries/Mouse/Mouse.h

@@ -22,7 +22,13 @@
 #ifndef MOUSE_h
 #define MOUSE_h
 
-#if 1 //defined(USBCON)
+#if defined(_USING_HID)
+
+#error "Can only attach one submodule to HID module"
+
+#else
+
+#define _USING_HID
 
 #include "HID.h"
 //================================================================================

libraries/MouseAndKeyboard/MouseAndKeyboard.h

@@ -1,6 +1,12 @@
 #ifndef MOUSEANDKEYBOARD_h
 
-#if 1 //defined(USBCON)
+#if defined(_USING_HID)
+
+#error "Can only attach one submodule to HID module"
+
+#else
+
+#define _USING_HID
 
 #include "HID.h"
 //================================================================================