* Don't call gtk_widget_show_all() on popup dialog.
Fixes#15317.
Notes: Fixed incorrect display of some GtkMessageDialog icons.
The issue is caused because GtkMessageDialog contains an icon widget
which is not shown when there's no associated icon. Our call to
`gtk_widget_show_all()` overrides this, showing the uninitialized
icon widget.
This PR fixes the issue by calling `gtk_widget_show()` where needed
and removing use of `gtk_widget_show_all()` in the message dialog.
* use gtk_dialog_set_default_response() for default
* fix: support icons on gtk+ messageboxes.
869e0ab14d