Make bubble view canvas finite

[dotmacro]

Problem

After the first article is created, in bubble view the user can scroll the bubble section very far (potentially infinitely) in both the X and Y direction. Once the bubbles are out of the viewable area, it can be difficult for the user to find them again.

Note: This does not seem to apply to new subjects with no article.

Solution

The bubble view should be bounded so, at minimum, part of a bubble is always in the viewable area.