Purpose

Fixes a bug which would make the preview hide even when the mouse was
moved over a visible part of it. This happened only when the preview
area was wider than the node.

The cause of the bug I would argue is some very strange behavior of
HitTest. When run on the NodeView, this test would not consider the
right part of the preview, like if the box was as wide as the node but
displaced to the left.

Likewise, running a HitTest on the PreviewControl itself provided
inconsistent results. Initially this would work as expected, but after
the preview was expanded and recondensed, the box would remain forever
bloated as if still expanded. This resulted in inconsistencies with the
leave event, which used the real margins of the control.

The problem was fixed by checking explicitly that the preview visible
area is abandoned before hiding the preview.

Declarations

Check these if you believe they are true

• The codebase is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.
• Changes to the API follow Semantic Versioning and are documented in the API Changes document.

Reviewers

@QilongTang @mjkkirschner

FYIs

@DynamoDS/dynamo