Cell Grid Safe Area [was Re: ISSUE-163 (Cell units): Clarify use of cell units in certain properties [DFXP 1.0]]

On Tue, Mar 13, 2012 at 11:30 AM, John Birch <John.Birch@screensystems.tv>wrote:

>  Cell grid is taken from root extent, which implies that cell 0, 0 is at
> the top left boundary of the root extent.
>
> Unfortunately in practise this is often undesirable as it is unlikely that
> you would want text placed so close to the boundary of the root extent.***
> *
>
> Is there any *padding* *like* mechanism that would allow a ‘safe area’ to
> be defined around the edge of the ‘virtual grid’ created by cell resolution.
>

We do not define that the root container is coterminous with the visible
screen. The external authoring context determines the origin of the root
container. I believe we have assumed that all of the root container is
within a safe area, but I agree that the spec does not specifically read on
this point.