GtkEntryCompletion popup size

[Dave Howorth <dhoworth mrc-lmb cam ac uk>]

I'm using a GtkEntryCompletion in popup-mode and controlling the list of
matches myself. I see that it displays up to 15 matches and if there are
more it adds a scroll bar to the popup window.

For my purposes it doesn't seem worthwhile to have a scroll bar. Is
there any way to control whether or when a scroll bar is added? Or is
there any way to discover the maximum number of rows that will be
visible in the popup? Or is it always guaranteed to be 15?

Thanks, Dave