ID 252227 - Scrollbar doesn’t appear in NetworkMaterial tree widgets

Problem summary
When viewing a NetworkMaterial’s material.nodes attribute in the Attributes tab, no scrollbar appears when the nodes are expanded beyond the tree widget’s box size, and the box is not resizeable.
It is necessary to resize the tab to get a scrollbar to appear.

Steps to reproduce

1. Open the attached reproduction scene, or create a shading network with 4 connected nodes going into a NetworkMaterial.

2. View the scene graph from the NetworkMaterial node and open its attributes.

3. In the Attributes tab, expand to material.nodes and expand the individual nodes in the tree widget. The nodes will be expanded beyond the size of the box, but there is no scrollbar to view the lower nodes.

4. Slightly adjust the width of the Attributes tab. A scrollbar will appear.
   

   

Workaround
Change the width of the Attributes tab very slightly to get a scrollbar to appear.

Reproduced by support
Katana 1.6v3, 2.0v1, 2.0v5, 2.1v1, 2.1v5, 2.5v1, 2.5v4 RHEL 6.3
Katana 2.5v1, 2.5v4 Windows 7

Expected behaviour
A scrollbar should appear as soon as the tree view is expanded beyond what is visible in the box.

Actual behaviour
It is necessary to resize the tab to make the scrollbar appear.