This only applies if you have custom .js files for widgets.
Most widgets now inherit from WidgetBaseXSL (which inherits from
WidgetBase) to apply the XSL transform to generate widget output.
But widgets can also define their own paint method and inherit from WidgetBase instead
(e.g. AOIBoxDHTML uses pure DHTML to create output).
Between v0.4 and 1.0, the widget inheritance model was changed and also includes using the .apply() method to implement inheretance.
This was to allow much more flexibility in how widgets implement the
paint() method, and using .apply cleans up some unnecessary code.
However it also means that the function signature of the base classes has changed.
This means that if you have any custom widget .js file, you will have to change the way
the base constructors are called.
Instead of this:
It's a very straighforward change but your 0.4 widgets won't work until you make this change.
A similar change was made to the Model base classes.