The CommandButton openContentPane is currently only supported when the commandButton is inside a contentStack. It would be useful to support this attribute outside of a contentStack so a commandButton could use the openContentPane attribute in places such as a pagePanel header outside of a contentStack.

It would be good to avoid forcing the developer to specify the contentStack with a new attribute, so the following algorithm might be workable.

1. Search for the contentStack in the parent hierarchy.
2. If not found, search for the first content stack, top down, from the root of the component tree.

This will have the constraint that if the commandButton is not nested within the contentStack, the openContentPane attribute will only work with the first located contentStack, so using this with multiple contentStacks on the the page, in this context, should be avoided.