gtk_widget_set_margin_end has no effect

[Alex <acs82 gmx de>]

H gtk-devs,

could it possibly be that "gtk_widget_set_margin_end"/"gtk_widget_set_margin_right" is ignored if the used 
theme already defines a value for "margin-right" ?

I have a custom widget which has GtkToggleButtonClass as parent.

For my widget it seems like "gtk_widget_set_margin_end"/"gtk_widget_set_margin_right" has no effect at all.

However if I change the style-property via css:

gtk_css_provider_load_from_data (provider, " .toggle { margin-right: 0; }", -1, NULL);

Than I get the needed effect.

Why this is the case ?

I am using gtk3 v.  3.22.11-1

Thanks & Cheers,

Alex