Add signal InputRedirection::keyStateChanged

Complements all other signals for internal usage that there is an
input event.

Needed by e.g. DPMS implementation to re-enable the outputs.

input.cpp

@@ -855,6 +855,7 @@ void InputRedirection::updateKeyboardWindow()
 
 void InputRedirection::processKeyboardKey(uint32_t key, InputRedirection::KeyboardKeyState state, uint32_t time)
 {
+    emit keyStateChanged(key, state);
     const Qt::KeyboardModifiers oldMods = keyboardModifiers();
     m_xkb->updateKey(key, state);
     if (oldMods != keyboardModifiers()) {

input.h

@@ -182,6 +182,13 @@ Q_SIGNALS:
      * @param oldMods The previous modifiers state
      */
     void keyboardModifiersChanged(Qt::KeyboardModifiers newMods, Qt::KeyboardModifiers oldMods);
+    /**
+     * @brief Emitted when the state of a key changed.
+     *
+     * @param keyCode The keycode of the key which changed
+     * @param oldMods The new key state
+     */
+    void keyStateChanged(quint32 keyCode, InputRedirection::KeyboardKeyState state);
 
 private:
     static QEvent::Type buttonStateToEvent(PointerButtonState state);