UCI getFormContext does not exist

Hi team, 

I created a button ion my ribbon and I pass two parameter in the js function 

showme(pPrimaryControl, pEntityid)....

suppostly pPrimaryControl has a getFormContext but I only see GlobalContext function. In this function I am trying to get some control value, but is impossible.

Somebody knows how I can use this context? when I use a ribbon button this method (getFormContext) is available?