/* $Id$/

Cell Content		Jody Goldberg <jody@gnome.org>


Overview
    GnmCell is one of the most widely used aspects of Gnumeric.  This document
    describes the operations and state changes that are available.

Content
    location : Cells contain pointers to their sheet, the row, and the column
               that contains them.  This may change.

    value : A GnmValue *.  All displayable cells should have a value.

    renderedvalue : A placeholder for future use.

LifeCycle

    When a cell is first created it is initialized to have value_empty and no location.

Actions
    - Mark sheet as dirty
    - Queue depends for recalc
    - Calculate
    - Render
    - Dimension
    - Spans
    - Redraw
    - link expression to master list
    - Update the edit area
    - Recalc the auto expression

Future plans
    - just in span calculation
    - span ovelap
    - Have spans use run length encoding