Create a new GtkSourceCompletionContext for completion. The position where
the completion occurs can be specified by position. If position is NULL,
the current cursor position will be used.
a new GtkSourceCompletionContext. The reference being returned is a 'floating' reference, so if you invoke gtk_source_completion_show() with this context you don't need to unref it. [transfer floating]
Create a new GtkSourceCompletionContext for completion. The position where the completion occurs can be specified by position. If position is NULL, the current cursor position will be used.