Fix: Nested Draggables

[lambdaschmied2]

Instead of returning cs in -measure return (core/measure child _ctx cs)

Donno what cs does or stands for, but I suppose it was just a placeholder ^^

[tonsky]

cs is short for “constraints”

Can you modify an example so that it demonstrates the behaviour that you fixed? I’m not sure I understand what you fixed (or what was broken) in video in #74

[tonsky]

Also, function arguments that start with underscore mean “not currently used in function body”. If you pass it to the child, it should not contain underscore