This generic hook function is called whenever a grid grob is edited
This provides an opportunity for customising the editing of a
new class derived from grob (or gTree).
A grid grob.
A list of named elements. The names indicate the grob slots to modify and the values are the new values for the slots.
This function is called by
A method should be written for classes derived from grob or gTree
if a change in a slot has an effect on other slots in the grob or
children of a gTree (e.g., see
Note that the slot already has the new value.
The function MUST return the modified grob.