fix: client to server modifier press/release

Pressing a modifier on the client and moving to the server and releasing
it breaks the modifier on the client. This resolves the issue.

src/lib/deskflow/IKeyState.h

@@ -103,6 +103,16 @@ public:
   */
   virtual void fakeAllKeysUp() = 0;
 
+  //! Clear stale modifiers
+  /*!
+  Clears stuck modifier state in platform-specific keyboard tracking (e.g. XKB).
+  Default implementation does nothing.
+  */
+  virtual void clearStaleModifiers()
+  {
+    // Default implementation does nothing
+  }
+
   //! Fake ctrl+alt+del
   /*!
   Synthesize a press of ctrl+alt+del.  Return true if processing is

src/lib/deskflow/IPlatformScreen.h

@@ -187,6 +187,7 @@ public:
   KeyModifierMask pollActiveModifiers() const override = 0;
   int32_t pollActiveGroup() const override = 0;
   void pollPressedKeys(KeyButtonSet &pressedKeys) const override = 0;
+  void clearStaleModifiers() override = 0;
 
 protected:
   //! Handle system event

src/lib/deskflow/KeyState.cpp

@@ -760,6 +760,7 @@ void KeyState::updateKeyState()
   }
 
   // get the current modifier state
+  clearStaleModifiers();
   m_mask = pollActiveModifiers();
 
   // set active modifiers

src/lib/deskflow/PlatformScreen.cpp

@@ -85,6 +85,11 @@ void PlatformScreen::pollPressedKeys(KeyButtonSet &pressedKeys) const
   getKeyState()->pollPressedKeys(pressedKeys);
 }
 
+void PlatformScreen::clearStaleModifiers()
+{
+  getKeyState()->clearStaleModifiers();
+}
+
 int32_t PlatformScreen::mapClientScrollDirection(int32_t x) const
 {
   return (m_invertScrollDirection ? -x : x);

src/lib/deskflow/PlatformScreen.h

@@ -62,6 +62,7 @@ public:
   KeyModifierMask pollActiveModifiers() const override;
   int32_t pollActiveGroup() const override;
   void pollPressedKeys(KeyButtonSet &pressedKeys) const override;
+  void clearStaleModifiers() override;
 
   // IPlatformScreen overrides
   void enable() override = 0;

src/lib/platform/EiKeyState.cpp

@@ -309,4 +309,13 @@ void EiKeyState::updateXkbState(uint32_t keyval, bool isPressed)
   xkb_state_update_key(m_xkbState, keyval, isPressed ? XKB_KEY_DOWN : XKB_KEY_UP);
 }
 
+void EiKeyState::clearStaleModifiers()
+{
+  // Recreate the XKB state to clear stuck modifiers that happen when
+  // modifier keys are press on client and released on server
+  if (m_xkbState) {
+    xkb_state_unref(m_xkbState);
+  }
+  m_xkbState = xkb_state_new(m_xkbKeymap);
+}
 } // namespace deskflow

src/lib/platform/EiKeyState.h

@@ -35,6 +35,7 @@ public:
   void pollPressedKeys(KeyButtonSet &pressedKeys) const override;
   KeyID mapKeyFromKeyval(std::uint32_t keyval) const;
   void updateXkbState(std::uint32_t keyval, bool isPressed);
+  void clearStaleModifiers() override;
 
 protected:
   // KeyState overrides