Re: Please help (core dump)

[Carlo Wood <carlo alinoe com>]

Hi Kjell,

thank you so much for helping me out!

I'm not sure what you mean with doing

LinuxChessboardWidget(......) : Glib::ObjectBase("myWidgetClass")

since Glib::ObjectBase is a base class of Gio::ActionMap,
I can't call that from LinuxChessboardWidget no?

What I have is the following:

class LinuxChessApplication : public Gtk::Application
{
...
  void on_menu_file_exit();

Where 'Exit' is not related to a single window, but is application
wide (it closes all windows and exits the application).
I add this with add_action to Gtk::Application.

Then I have:

class LinuxChessWindow : public Gtk::ApplicationWindow
{
...
  void on_menu_file_load();
  void on_menu_file_save();
  void on_menu_game_new();
  void on_menu_game_clear();
  void on_menu_game_export();
  void on_menu_game_undo();
  void on_menu_game_flip();
  void on_menu_mode_editposition();
  void on_menu_mode_editgame();

These are added, using add_action, to Gtk::ApplicationWindow.

So, I am using what you said. But, then I have:

class LinuxChessboardWidget : public cwmm::ChessPositionWidget
{
...
  void on_menu_mode_showcandidates();
  void on_menu_mode_showreachables();
  void on_menu_mode_showattacked();
  void on_menu_mode_showdefendables();
  void on_menu_mode_showdefended_black();
  void on_menu_mode_showdefended_white();
  void on_menu_mode_showmoves();
  void on_menu_mode_placepieces();

It is possible, though silly imho, to add those member funtions to
LinuxChessWindow (all those would do is call the member functions of
its LinuxChessboardWidget). So, I rather register these directly.

I couldn't think of another way than to derive LinuxChessboardWidget
from Gio::ActionMap, like Gtk::Application and Gtk::ApplicationWindow.

Should I add a Gio::SimpleActionGroup to LinuxChessboardWidget instead
and add them to that? If I do that, then how can get this
Gio::SimpleActionGroup to be used for my menu? And under what name
would do I have to refer to them in the `ui_info` xml string that
I use for my Gtk::Builder? Or should I use a separate Gtk::Builder?

With 'name' I mean that the menu entries that are added to
Gtk::Application are refered to as "app.*" and those that are
added to Gtk::ApplicationWindow are refered to as "win.*".
I'd like it when the methods of LinuxChessboardWidget can be
refered to as -say- "chessboard.*".


On Sun, 26 Jul 2020 11:06:53 +0200
Kjell Ahlstedt <kjellahlstedt gmail com> wrote:

> Gio::ActionMap is an interface. That's why its constructor is
> protected. An interface can't be instantiated by itself. It must be
> implemented by a class which can be instantiated. If you really must
> implement Gio::ActionMap in your class (which I doubt), there is one
> or (probably) two errors.
>
> First, interfaces must come before the widget class in the list of
> base classes.
>
> class LinuxChessboardWidget : public Gio::ActionMap, public
> cwmm::ChessPositionWidget
>
> This is opposite to what's done in gtkmm's classes that wrap gtk
> classes.
>
> Second, your constructor must call a special Glib::ObjectBase
> constructor that registers your class with its own GType in glib's
> GType system. For instance
>
> LinuxChessboardWidget(......) : Glib::ObjectBase("myWidgetClass")
> ..... // Or whatever you want to call it.
>
> This is an unusual way of using Gio::ActionMap. I don't know if these
> are the only necessary changes. Much more common is to use one of the
> classes that already implement Gio::ActionMap:
> Gio::SimpleActionGroup, Gtk::Application (via Gio::Application) or
> Gtk::ApplicationWindow.