! Sets the key of the graph's data point the tracer will be positioned at. This is the only free coordinate of a tracer when attached to a graph. Depending on \ref setInterpolating, the tracer will be either positioned on the data point closest to \a key, or will stay exactly at \a key and interpolate the value linearly. \see setGraph, setInterpolating */
source not stored for this graph (policy: none)
nothing calls this directly
no outgoing calls
no test coverage detected