Add functions to show GUI windows (bug #57213) * event-manager.h (interpreter_events::focus_window): New empty method. (event_manager::focus_window): New vistual method that executes the instance's focus_window method. * event_manager.cc (commandwindow, commandhistory, filebrowser, workspace): New builtin interpreter functions. * qt-interpreter-events.[h, cc] (qt_interpreter_events::focus_window_signal): New signal. (qt_interpreter_events::focus_window): Implements event_manager::focus_window, emits focus_window_signal. * main-window.[h, cc] (main_window::focus_window): New slot that activates the named window. * octave-qobject.cc (gui_qobject::gui_qobject): Connect qt_interpreter_events::focus_window_signal to main_window::focus_window. * __unimplemented__.m: Remove commandwindow, commandhistory, filebrowser, and workspace from the list. * gui.txi: Add commandwindow, commandhistory, filebrowser, workspace docstrings.

--- a/libinterp/corefcn/event-manager.h	Mon Nov 11 20:22:52 2019 +0100
+++ b/libinterp/corefcn/event-manager.h	Tue Nov 12 14:54:25 2019 +0100
@@ -184,6 +184,9 @@
       return false;
     }
 
+    virtual void focus_window (const std::string /*win_name*/)
+    { }
+
     virtual void
     execute_command_in_terminal (const std::string& /*command*/) { }
 
@@ -458,6 +461,12 @@
       return enabled () ? instance->copy_image_to_clipboard (file) : false;
     }
 
+    virtual void focus_window (const std::string win_name)
+    {
+      if (enabled ())
+        instance->focus_window (win_name);
+    }
+
     // Preserves pending input.
     void execute_command_in_terminal (const std::string& command)
     {