make-overlay and endpoints

Hi all I have encountered an issue with respect to compatibility between Emacs overlays and our extents. Here's what the GNU Emacs List Reference Manual says: “The arguments front-advance and rear-advance specify the marker insertion type for the start of the overlay and for the end of the overlay, respectively. See Marker Insertion Types. If they are both nil, the default, then the overlay extends to include any text inserted at the beginning, but not text inserted at the end.” This appears to be the same as with extents. However, when creating an overlay in Emacs that has identical start and end positions and the default endpoint properties, then deleting characters at that position does not delete the overlay. In XEmacs 21.5.34 doing the same with an extent (start-closed/end-open) removes the extent from the buffer. “Deletion of a character on a side of a zero-length extent whose corresponding endpoint is closed causes the extent to be detached if its `detachable' property is set; if the corresponding endpoint is open, the extent remains in the buffer, moving as necessary.” What exactly does “a character on a side” mean. I can only delete a character “at” the extent. In which case the start-closed seems to have a higher priority. In the case at hand this is easy enough to work around, but I am wondering if that difference is deliberate, whether it may make sense to change the behavior or whether to tell authors to not rely on either behavior since it is a nasty corner case scenario anyway. Thanks Marcus _______________________________________________ XEmacs-Beta mailing list XEmacs-Beta(a)xemacs.org http://lists.xemacs.org/mailman/listinfo/xemacs-beta