LINE:interactive_drawing

Xwindows

 When running under X windows, mouse button 2 toggles the continuous
 display of the graphics cursor location. The PHYSICA keyword CUNITS
 is the units type for these numbers. If CUNITS = WORLD, the numbers
 depend on the current units type, either CM or IN, as chosen with SET
 UNITS. If CUNITS = GRAPH, the numbers displayed depend on the current
 graph axis scales. If CUNITS = PERCENT, the numbers depend on the
 current window.

HV

 If the \HV qualifier is used, the line segments will be forced to be
 either horizontal or vertical.