Producer capable of generating or otherwise obtaining AbstractHelpScopes
for filtering the help system. Scopes can be defined either by adding a
'scope' or 'scopeProducer' element to the
"org.eclipse.help.base.scope" extension point.
The 'scopeProducer' allows for runtime scopes to be created.
Obtains a list of IScopeHandles, which in turn will contain
AbstracHelpScope implementations. Use this method to create
or load AbstractHelpScopes at runtime.
Returns:
an array of the contributed scope handles. May not be null.