ID 321055 - ViewerAPI: Viewport::freeze() and Viewport::thaw() functions are never called

Problem summary
The Viewport::freeze() and Viewport::thaw() functions are not called on a custom Viewport implementation when the Katana window is minimised/maximised.

Customer reported version
Katana 3.0v1.001216a

Customer reported platform
ubuntu

Workaround
Manually call the functions from the respective ViewerDelegate functions.

Reproduced by Support
This bug occurs in previous builds from the 2.6 line up to the latest 3.0.1-001216a build

Expected behaviour
The Viewport::freeze() and Viewport::thaw() functions should be called when the Katana window is minimised/maximised.

Actual behaviour
These functions are never called