`oxf.fr.detail.button.$button.visible` doesn't support `fr:control-string-value()`

[ebruchez]

This started happening since we introduced fr:buttons-bar. The evaluation context of the visibility expressions is now inside an XBL component. We use xxf:evaluate() for those.

Considering a way to tell to evaluate the expression in a given XForms context:

• adding parameter to xxf:evaluate()
• or adding a new function

We only document a single parameter to xxf:evaluate(), although on the JVM we just delegate to saxon:evaluate() which can take more parameters. On JS, we only implement one parameter, the XPath expression as string.

+1 from customer

[ebruchez]

• [x] fix
• [x] add support for $control notation

[ebruchez]

For the $control notation, the expression must be processed through replaceVarReferencesWithFunctionCallsFromString(). It is desirable not to do this at each evaluation of a button's visibility, which means this should be cached.

An obvious place to do this is in the properties, as we cache a result associated with that.

[ebruchez]

Cool, @avernet just added replaceVarReferencesWithFunctionCallsFromProperty() :)

[ebruchez]

• [x] test