This method allows you to set any of the flags defined by the GtkWidgetFlags enumerated values. These flags share the flags space in GtkObject; the first four bits are taken by GtkObjectFlags, and derived objects use the remaining bitfields. The GtkWidgetFlags settings determine the capabilities of a widget; e.g the flag GTK_NO_WINDOW is set on certain widgets during their creation in the GTK source, reversing the generic widget property of $widget->window; - such widgets are not able to respond unilaterally to GDK events. (Use a GtkEventBox to capture events on windowless widgets.)

You would use set_flags() in a situation where the widget needs capabilities it does not have at base; setting for instance GTK_CAN_DEFAULT on a GtkButton you want to have keyboard grab by default will cause that button to be drawn in such a way that space is allowed for it to be displayed with default status.

Although all the flag bitfields are reversible in this way, it is not always sane to alter them, given that the chief characteristics of a widget are controlled by them. For example, unsetting the GTK_NO_WINDOW flag on a GtkLabel widget will prevent the label from displaying its current text.

See also: flags() , unset_flags() , and a whole host of GtkWidget methods such as set_sensitive() and grab_default() which either act as wrappers for the set_flags() function or need to work in tandem with GtkWidgetFlags values set in this way.