format_heading_markup

Sets the formatted heading of this with Pango markup.

The format is assumed to contain Pango markup.

Special XML characters in the `printf()` arguments passed to this function will automatically be escaped as necessary, see [ func@GLib.markup_printf_escaped].

See [property@MessageDialog:heading].

Parameters:

this	a message dialog
format	the formatted string for the heading with Pango markup
...	the parameters to insert into format