Using the DialogHandler, the targetWidth/targetHeight parameters have to be defined at dialog, because I don't see a clean way of getting back to the control holding the rest of the configuration. If we introduce a postSave mechanism in 3.1, it should somehow get a map of control config nodes / saveInfo to be able to set the target size at control level.
for 3.0 compatibility, we're providing a DialogHandler (extends ParagraphEditDialog)
for 3.1, we will potentially introduce a postSave() mechanism on the SaveHandler