Developing a DSL Graphical Notation - Eclipse Modeling Project: A Domain-Specific Language Toolkit - page 116

We plan to implement a custom EditPolicy for our ToolTip, which is the
standard GEF approach for adding behavior to an EditPart . It might seem like
overkill when you see the actual implementation, but this gives us an opportu-
nity to illustrate this extension approach.
The GMF generator model enables us to define Custom Behaviour ele-
ments as children of Gen Top Level Node elements. We need to add a refer-
ence from our Tooltip class to this element in the GMF generator model. Using
the Load Resource menu followed by the convenient Browse Registered
Packages button brings up the dialog shown in Figure 4-21. It takes a few sec-
onds to populate, but when it does, we select our GMF GenModel from the list.
Be sure to select Runtime Version and not Development Time Version , and then
accept the corresponding warning that models referenced in this manner will not
appear as a root in the editor. Selecting Runtime Version means that references
to this loaded model will use the registered package Namespace URI instead of
a platform:/ URI, as is the case when selecting Development Time Version .

Figure 4-21 Package Selection dialog

We now create an editpolicy reference from our Tooltip class to the
CustomBehaviour class in the loaded GMF GenModel. To reference the text
we need to display in our ToolTip, we add a reference to the Ecore EAttribute
element. Similar to our earlier procedure, we first use the Load Resource menu
item to add the http://www.eclipse.org/emf/2002/Ecore model to our