Re: gtk_menu_item_set_accel_path()

[Christian Schoenebeck <schoenebeck linuxsampler org>]

On Donnerstag, 8. Februar 2018 12:17:06 CET Daniel Boles wrote:
> > are correctly updated with the expected textual representation of the
> > keyboard
> > accelerator key(s) (i.e. "Ctrl c", "F1", etc.), however the menu item's
> > GtkAccelLabel would never be displayed on screen.
>
> I think we'd need to see precisely how you're setting up this MenuItem to
> do anything other than speculate wildly.

Hi Daniel,

first of all, the application code to reproduce this issue is actually gtkmm 
code and it is perfectly working with gtkmm2 & Gtk2. After investigating this 
a bit further, it seems to be a bug on gtkmm(3) level rather than on gtk(3) 
level, but I am not absolutely sure yet.

Here is the setup, first as gtkmm C++ code (followed by unwrapped gtk C code):

// MainWindow being subclass of Gtk::Window
MainWindow::MainWindow() {
        ...
        // create a global keyboard acceleration entry for Shif+F1 and acceleration 
        // path to be named "<Foo>/bla"
        Gtk::AccelMap::add_entry("<Foo>/bla", GDK_KEY_F1, Gdk::SHIFT_MASK);

        // actually creates (implied) a new acceleration group and assigns it to 
        // window
        Glib::RefPtr<Gtk::AccelGroup> accelGroup = this->get_accel_group(); 

        // assign newly created acceleration group to menu
        menu->set_accel_group(accelGroup);

        // add menu item to menu
        Gtk::MenuItem* menuItem = new Gtk::MenuItem("Some text");
        menu->append(menuItem);

        // assign keyboard acceleration path to menu item
        menuItem->set_accel_path("<Foo>/bla");

        // assign a callback as action when either menu item is clicked or 
        // triggered by keyboard accelerator
        menuItem->signal_activate().connect(
                sigc::men_fun(*this, &MainWindow::doSomething)
        );
}

That gtkmm code still provides its expected base functionality with gtkmm3, 
that is the menu item's action is triggered correctly when the keyboard 
accelerator is used, but unlike with gtkmm2 the accelerator keys are no longer 
displayed in the menu with gtkmm3.

Now unwrapped as gtk C code it would look like this:

        // create a global keyboard acceleration entry for Shif+F1 and acceleration 
        // path to be named "<Foo>/bla"
        gtk_accel_map_add_entry("<Foo>/bla", GDK_KEY_F1, GDK_SHIFT_MASK);

        // create an acceleration group and assign it to main window and menu
        GtkAccelGroup* accelGroup = gtk_accel_group_new();
        gtk_window_add_accel_group(mainWindow, accelGroup);
        gtk_menu_set_accel_group(menu, accelGroup);

        // add menu item to menu
        GtkWidget* menuItem = gtk_menu_item_new_with_label("Some text");
        gtk_menu_shell_append(menu, menuItem);

        // assign keyboard acceleration path to menu item
        gtk_menu_item_set_accel_path(GTK_MENU_ITEM(menuItem), "<Foo>/bla");

        gtk_widget_show(menuItem);

        // assign a callback as action when either menu item is clicked or 
        // triggered by keyboard accelerator
        g_signal_connect( G_OBJECT(menuItem), "activate",                                   
                G_CALLBACK(doSomething), NULL );

And in fact that C code works perfectly even with Gtk 3, but gtkmm3 is doing 
something differently than in above's C code: in the Gtk::MenuItem constructor 
they explicitly create an acceleration label for the menu item and I am not 
sure whether they should not do that, or whether gtk should rather be able to 
handle that:

        https://github.com/GNOME/gtkmm/blob/gtkmm-3-22/gtk/src/menuitem.ccg
        (line 46 and line 51-61 being the relevant ones) 

As far as I can read from the gtk sources, gtk automatically creates the menu 
item's acceleration label (even if no accelerators are used at all). But right 
now I cannot judge which side is wrong here (gtkmm3 or gtk3).

> Isn't this a tautology? Why would the size be updated for an accelerator
> that is not being shown...?

Well, if I force a greater allocation size for the menu item, the accelerator 
is in fact displayed (even with gtkmm3 that is).

CU
Christian