Add: News menu entry and shortcut for deleting all messages. (#7240)

src/window.cpp

@@ -39,6 +39,7 @@
 #include "framerate_type.h"
 #include "network/network_func.h"
 #include "guitimer_func.h"
+#include "news_func.h"
 
 #include "safeguards.h"
 
@@ -3370,6 +3371,17 @@ restart_search:
 	}
 }
 
+/**
+ * Delete all messages and their corresponding window (if any).
+ */
+void DeleteAllMessages()
+{
+	InitNewsItemStructs();
+	InvalidateWindowData(WC_STATUS_BAR, 0, SBI_NEWS_DELETED); // invalidate the statusbar
+	InvalidateWindowData(WC_MESSAGE_HISTORY, 0); // invalidate the message history
+	DeleteWindowById(WC_NEWS_WINDOW, 0); // close newspaper or general message window if shown
+}
+
 /**
  * Delete all windows that are used for construction of vehicle etc.
  * Once done with that invalidate the others to ensure they get refreshed too.