UserInputHandler: add virtual method OnRawKey()

src/AsyncUserInput.cxx

@@ -55,6 +55,12 @@ AsyncUserInput::OnSocketReady(unsigned) noexcept
 	}
 #endif
 
+	if (handler.OnRawKey(key)) {
+		// TODO: begin_input_event() ?
+		end_input_event();
+		return;
+	}
+
 	Command cmd = translate_key(key);
 	if (cmd == Command::NONE)
 		return;

src/Instance.cxx

@@ -82,3 +82,10 @@ Instance::Run()
 
 	event_loop.Run();
 }
+
+bool
+Instance::OnRawKey(int key) noexcept
+{
+	(void)key;
+	return false;
+}

src/Instance.hxx

@@ -119,6 +119,7 @@ private:
 #endif
 
 	// virtual methods from AsyncUserInputHandler
+	bool OnRawKey(int key) noexcept override;
 	bool OnCommand(Command cmd) noexcept override;
 #ifdef HAVE_GETMOUSE
 	bool OnMouse(Point p, mmask_t bstate) noexcept override;

src/UserInputHandler.hxx

@@ -15,6 +15,16 @@ struct Point;
  */
 class UserInputHandler {
 public:
+	/**
+	 * Implementing this method gives the handler a chance to
+	 * handle a key code pressed by the user.  This is called
+	 * before looking up hot keys.
+	 *
+	 * @return true if the character was consumed, false to pass
+	 * it on to the hot key checker
+	 */
+	virtual bool OnRawKey(int key) noexcept = 0;
+
 	/**
 	 * A hot key for a #Command was pressed.
 	 *