Computes the common prefix that is shared by all rows in completion that start with key.
If no row matches key, null will be returned. Note that a text column must have been set for this function to work, see gtk.entry_completion.EntryCompletion.setTextColumn for details.
The text to complete for
The common prefix all rows starting with key
Deprecated: GtkEntryCompletion will be removed in GTK 5.
Computes the common prefix that is shared by all rows in completion that start with key.
If no row matches key, null will be returned. Note that a text column must have been set for this function to work, see gtk.entry_completion.EntryCompletion.setTextColumn for details.