title: determining the intrinsic size of a UIStackView before display on the screen
body: <p>I would like to determine the instrinstic size of a stack view before displaying it on the screen. The idea is to use it as part of a pull up menu from the bottom of the screen but when I query the object before it appears it has size (-1,-1). Is there anything I should do first before my call to instrinsic content size?</p>