gtk:stack-interpolate-size (object)

object -- a gtk:stack widget
interpolate -- true if child sizes are interpolated

The accessor for the interpolate-size slot gets or sets whether the stack is set up to interpolate between the sizes of children on page switch. If the interpolate-size property is set to true, the stack will interpolate its size between the current one and the one it will take after changing the visible child, according to the set transition duration.