#4 Validation of drag and drop edits

[Mike Henderson]

If components have restrictions on where they can be
placed, such as some of the contrib library table
components, or the core form related components which
must appear inside a form, the palette should reject
edits that violate these restrictions.

Since this is a feature that applies to third-party
component libraries as much as the core libraries the
solution should support validation of component edits
as part of the shipped component library

Perhaps develop an interface or class name pattern that
library implementors can deliver inside the component
library JAR file. The palette can provide the library
code with method arguments containing a DOM
representation of the template, or a tree
representation of the component heirarchy in the
template along with a proposed location in the
hierarchy at which a component will be placed as well
as the name of the component.

The library code can query the arguments and validate
that it is appropriate to place the component at the
provided location in the hierarchy. If not appropriate,
then throw an exception with a message (i18n) which can
be displayed to the user and trigger the edit to be
rejected.

This feature could also be incorporated into Spindle