GTK+ 3 transition: Use accessor functions

[charles]

GTK+ 3.0 is making most GTK+ struct's fields private. Instead of using direct access, the fields must be read by accessor methods. More background information on this can be found at ​http://live.gnome.org/GnomeGoals/UseGseal

[charles]

r11567: use gtk_dialog_content_area() instead of GTK_DIALOG(w)->vbox

[charles]

r11589: don't directly access GtkCellRenderer?.xpad, GtkCellRenderer?.ypad, or GtkWidget?.window.

[ijuxda]

gtr_cell_renderer_get_padding( &cell->parent, &xpad, &ypad );

Shouldn't that be

gtr_cell_renderer_get_padding( GTK_CELL_RENDERER( cell ), &xpad, &ypad );

?

[charles]

I don't see the benefit of adding redundant RTTI... by the time we reach that point in the code, we already know that cell is a valid TorrentCellRenderer? pointer.

[ijuxda]

1. The point of this ticket was to remove direct references to struct fields.
2. There is no precedent for such an access style in all of gtk.
3. The type macro expands to a pointer cast for release builds, not rtti.
4. The type macro works even if the name of the embedded struct changes.
5. The type macro works even if TorrentCellRenderer? does not directly derive from GtkCellRenderer?.

[charles]

Those are good points. I agree.

Added to trunk in r11601.