validDetails  Customising grid grob Validation 
 Description
This generic hook function is called whenever a grid grob is created or edited via grob, gTree, grid.edit or editGrob. This provides an opportunity for customising the validation of a new class derived from grob (or gTree). 
Usage
validDetails(x)
Arguments
| x | A grid grob. | 
Details
This function is called by grob, gTree, grid.edit and editGrob. A method should be written for classes derived from grob or gTree to validate the values of slots specific to the new class. (e.g., see grid:::validDetails.axis). 
Note that the standard slots for grobs and gTrees are automatically validated (e.g., vp, gp slots for grobs and, in addition, children, and childrenvp slots for gTrees) so only slots specific to a new class need to be addressed. 
Value
The function MUST return the validated grob.
Author(s)
Paul Murrell
See Also
    Copyright (©) 1999–2012 R Foundation for Statistical Computing.
Licensed under the GNU General Public License.