If you need to get the Y position of a vertically scrolling container, create a text box. Then on the container scroll trigger, set a variable that evaluates the numerical callback value from the event (Y position). Then add a callback that changes the text property of the text box by reading from the variable.

Design of play store.

An extended collection of fully animatable UI libraries like triangles, stars, arrows and more, let you bring your idea to life all within Proto.io.

This is an expand/collapse menu example that can be created using container states.

An example of a sticky scrolling sidebar (website)