Platform: don't leak XApplication modifiers into buttons and vice versa.

Couldn't discover this without having them actually printed in the test.

src/Magnum/Platform/AbstractXApplication.cpp

@@ -169,18 +169,18 @@ bool AbstractXApplication::mainLoopIteration() {
             /* Key/mouse events */
             case KeyPress:
             case KeyRelease: {
-                KeyEvent e(static_cast<KeyEvent::Key>(XLookupKeysym(&event.xkey, 0)), static_cast<InputEvent::Modifier>(event.xkey.state), {event.xkey.x, event.xkey.y});
+                KeyEvent e(static_cast<KeyEvent::Key>(XLookupKeysym(&event.xkey, 0)), event.xkey.state, {event.xkey.x, event.xkey.y});
                 event.type == KeyPress ? keyPressEvent(e) : keyReleaseEvent(e);
             } break;
             case ButtonPress:
             case ButtonRelease: {
-                MouseEvent e(static_cast<MouseEvent::Button>(event.xbutton.button), static_cast<InputEvent::Modifier>(event.xkey.state), {event.xbutton.x, event.xbutton.y});
+                MouseEvent e(static_cast<MouseEvent::Button>(event.xbutton.button), event.xkey.state, {event.xbutton.x, event.xbutton.y});
                 event.type == ButtonPress ? mousePressEvent(e) : mouseReleaseEvent(e);
             } break;
 
             /* Mouse move events */
             case MotionNotify: {
-                MouseMoveEvent e(static_cast<InputEvent::Modifier>(event.xmotion.state), {event.xmotion.x, event.xmotion.y});
+                MouseMoveEvent e(event.xmotion.state, {event.xmotion.x, event.xmotion.y});
                 mouseMoveEvent(e);
             } break;
         }

src/Magnum/Platform/AbstractXApplication.h

@@ -643,20 +643,24 @@ class AbstractXApplication::InputEvent {
         bool isAccepted() const { return _accepted; }
 
         /** @brief Modifiers */
-        Modifiers modifiers() const { return _modifiers; }
+        Modifiers modifiers() const {
+            return Modifiers(_modifiers & (ShiftMask|ControlMask|Mod1Mask|Mod5Mask|LockMask|Mod2Mask));
+        }
 
         /** @brief Mouse buttons */
-        Buttons buttons() const { return Button(static_cast<unsigned int>(_modifiers)); }
+        Buttons buttons() const {
+            return Buttons(_modifiers & (Button1Mask|Button2Mask|Button3Mask));
+        }
 
     #ifndef DOXYGEN_GENERATING_OUTPUT
     protected:
-        explicit InputEvent(Modifiers modifiers): _modifiers(modifiers), _accepted(false) {}
+        explicit InputEvent(unsigned int modifiers): _modifiers(modifiers), _accepted(false) {}
 
         ~InputEvent() = default;
     #endif
 
     private:
-        Modifiers _modifiers;
+        unsigned int _modifiers;
         bool _accepted;
 };
 
@@ -1014,7 +1018,7 @@ class AbstractXApplication::KeyEvent: public AbstractXApplication::InputEvent {
         Vector2i position() const { return _position; }
 
     private:
-        explicit KeyEvent(Key key, Modifiers modifiers, const Vector2i& position): InputEvent(modifiers), _key(key), _position(position) {}
+        explicit KeyEvent(Key key, unsigned int modifiers, const Vector2i& position): InputEvent(modifiers), _key(key), _position(position) {}
 
         const Key _key;
         const Vector2i _position;
@@ -1049,7 +1053,7 @@ class AbstractXApplication::MouseEvent: public AbstractXApplication::InputEvent
         Vector2i position() const { return _position; }
 
     private:
-        explicit MouseEvent(Button button, Modifiers modifiers, const Vector2i& position): InputEvent(modifiers), _button(button), _position(position) {}
+        explicit MouseEvent(Button button, unsigned int modifiers, const Vector2i& position): InputEvent(modifiers), _button(button), _position(position) {}
 
         const Button _button;
         const Vector2i _position;
@@ -1068,7 +1072,7 @@ class AbstractXApplication::MouseMoveEvent: public AbstractXApplication::InputEv
         Vector2i position() const { return _position; }
 
     private:
-        explicit MouseMoveEvent(Modifiers modifiers, const Vector2i& position): InputEvent(modifiers), _position(position) {}
+        explicit MouseMoveEvent(unsigned int modifiers, const Vector2i& position): InputEvent(modifiers), _position(position) {}
 
         const Vector2i _position;
 };