We've all seen this in numerous applications: checking a node in a checkbox tree widget selects all descendants and grays out all ancestors. Similarly, unchecking a node recursively executes the same logic in reverse. As a familiar example, the Resource Working Set dialog comes to mind (org.eclipse.ui.internal.dialogs.ResourceWorkingSetPage):
In fact, this behavior is so commonplace that if you've never used the JFace CheckboxTreeViewer class before, you might expect it to implement this behavior by default. However, this is not the case.
After reimplementing this behavior repeatedly in my applications, I finally made a simple helper class to make this process easier. To add this behavior to your CheckboxTreeViewer, simply add the following code, before setting the viewer input:CheckboxTreeSelectionHelper.attach(checkboxTreeViewer,myContentProvider);
Make sure your content provider implements getParent(), otherwise ancestor updates won't work correctly.
I've attached the helper class along with a complete example application. Hopefully this will make it easier for you to implement this commonplace checkbox tree behavior in your applications.
A word of caution: this code is provided as-is and has not undergone extensive testing. Please post any bug fixes or enhancements here.
Example app: CheckboxTreeSelectionHelperTestDialog.java