Search all objects of the selected layer's named rtree on the current sheet
and return a list of idpaths.
<p>
The first argument is a layer name with an optional suffix. A layer name
is the same as layer names printed by the GUI, e.g. "wire" or
"hub &amp; terminal". Suffix may be "-stroke" or "-fill"; when no
suffix is appended, "-stroke" is assumed. All normal objects are in
the stroke rtree; polygons with fill enabled are also in the fill rtree.
<p>
If coordinates of a box is give, smaller coords first, the search
is performed only within that box and any object that has overlapping
bounding box (on the given layer) is returned. Otherwise the search
is performed on the whole rtree, returning all objects on the layer.