Re: Impact of fix for bug 50339 on keyboard accessibility of panel

[Owen Taylor <otaylor redhat com>]

"Padraig O'Briain" <Padraig Obriain Sun COM> writes:

> The fix for bug 50339, setting a focus widget in a GtkWindow if it contains a 
> focusable widget, has caused me a problem with keyboard access to the panel.
> 
> Is it the intention of this bug fix that a GtkWindow should never have focus if 
> it contains a focusdable widget?

I don't think there is any new problem. With the default GtkWindow
code, the window itself is never in the tab chain. While the widget
came up in a buggy "no widget has focus" state, hitting Tab any number
of times would never return to that state.

I don't think treating "no widget has focus" as "window has focus" is
legitimate.  Characteristics of the focus widget include:

 - Has the HAS_FOCUS flag set on it if the toplevel has focus
 - gtk_widget_is_focus() returns TRUE for it
 - The ->focus_widget pointer of the toplevel points to it.

In _theory_ if a widget derived from GtkWindow wants to have a focus
state that was focus on itself, it would call gtk_widget_grab_focus ()
on itself to do that.

In practice, I'm pretty sure GTK+'s going to blow up if you did
that. We can fix that, and probably should. But see below for a more
immediate workaround.

> I need keyboard focus in the panel in order to access its context menu. I also 
> need keyboard focus on the objects on the panel.
> 
> I had done this by regarding focus on the panel as the BasePWidget, which 
> derives from GtkWindow, having focus.
> 
> Would the following change to gtkwindow.c be accepted?
> 
> Index: gtkwindow.c
> ===================================================================
> RCS file: /cvs/gnome/gtk+/gtk/gtkwindow.c,v
> retrieving revision 1.188
> diff -u -p -r1.188 gtkwindow.c
> --- gtkwindow.c	2002/01/30 23:35:08	1.188
> +++ gtkwindow.c	2002/01/31 13:31:18
> @@ -3039,7 +3039,7 @@ gtk_window_show (GtkWidget *widget)
>    /* Try to make sure that we have some focused widget
>     */
>    if (!window->focus_widget)
> -    gtk_window_move_focus (window, GTK_DIR_TAB_FORWARD);
> +    GTK_WINDOW_GET_CLASS (window)->move_focus (window, GTK_DIR_TAB_FORWARD);
>    
>    if (window->modal)
>      gtk_grab_add (widget);

No, I wouldn't consider it correct for a derived class to override
::move-focus, no.  ::move-focus is an action signal used to connect
key bindings to behavior; it's presence in the GtkWindow vtable is
purely accidental and results from the fact that we reuse the signal
mechanism to do key bindings.

And isn't what you are really trying to override is the (!window->focus_widget)
not the behavior of move_focus()?

I believe the simplest way of achieving your goals is to create a
dummy child widget to represent "focus on the panel" and to position
that at a position outside of bounds of the panel dialog widget so it
isn't visible.

Regards,
                                        Owen