[Gzz] New PEG: containment--benja

[Benja Fallenstein]

==================================================================
PEG ``containment--benja``: First cut at the containment mechanism
==================================================================

:Author:       Benja Fallenstein
:Date:         $Date: 2002/10/28 12:05:21 $
:Revision:     $Revision: 1.1 $
:Date-Created: 2002-10-28
:Status:       Current


Ted has specified a containment mechanism for zzstructure
[http://xanadu.com.au/mail/zzdev/msg01569.html]. I need this
implemented in Gzz for the email client.


Issues
------

- Viewing a cell containing other cells.
- Editing a cell containing other cells.

It would be possible to handle containment in the views,
but that would mean that the edit bindings would have to
be changed too; it would be more convenient to use the
``CellTexter`` interface.

However, this creates additional difficulties. As the very
first step, let's only do viewing, in the views; that means
that you can see the whole contained text, but you cannot
move the edit cursor beyond the first cell. As for the next
step, well, let's see what our experiences are.


Changes
-------

For now, let's handle containment through a
``gzz.zzutil.Contaiment`` class with the following methods::

   public static String getContainedText(Cell c) {
   // ...
   }

   public static Enfilade1D getContainedEnfilade(Cell c) {
   // ...
   }

These methods interpret the containment structure and return the
respective representation of the content.

Additionally, new ``p``/``P`` bindings as (IIRC) specified by Ted:
``p`` puts the left window's cell at the end of the right window's
list of contained cells; ``P`` does the reverse. (Actually, let's
use the prefix mechanism explained in PEG 1022: other window if
no cells are marked; the marked cells, if any; in the future,
the cell identified by number, if any.)

- Benja