In this paper, we consider the leader length minimization problem for boundary labelling, i.e. the problem of finding a legal leader-label placement, such that the total leader length is minimized. We present an O(n 2 log 3 n) algorithm assuming type-opo leaders (rectilinear lines with either zero or two bends) and labels of uniform size which can be attached to all four sides of rectangle R. Our algorithm supports fixed and sliding ports, i.e., the point where each leader is connected to the label (referred to as port) may be fixed or may slide along a label edge.

This work has partially been supported by the DFG grant Ka 512/8-3, by the German-Greek cooperation program GRC 01/048 and by the Operational Program for Educational and Vocational Training II (EPEAEK II) and particularly the Program PYTHAGORAS (co-funded by the European Social Fund (75%) and National Resources (25%)).