The next step in planning a reactor-based application is to determine how and when
to attach reactors. You need to attach two object reactors for the polyline border
of any garden path (one to respond to a modification event, the other to respond to
erasure), and one editor reactor to alert your application when users complete their
modification to the polyline. Object reactors are attached to entities, while editor
reactors are registered with AutoCAD.

There is another consideration to account for. To recalculate the polyline outline—return
it to a rectilinear shape—after the user modifies it, you must know what the vertex
configuration was before the modification. This information cannot be determined once
the polyline has been modified. By that time you can only retrieve information on
what the new configuration is. So how do you solve this? You could keep this information
in a global variable, but there is a major problem with that idea. Users can draw
as many garden paths as they want, and every new path would require a new global variable.