The ruler in SPLOT has many options, which can be accessed in the context menu called by a right mouse click in ruler:
Discern inactive parts - if checked, ruler will distinguish between active and inactive parts in the ruler. The inactive parts are those lying outside the drawing.
Show selection - if checked, ruler will reflect a selection rectangle for trimming etc.
Show measurement - if checked, ruler will reflect the measurement boundaries (i.e. only vertical and horizontal projections of the distance boundaries).
Show values - select here what additional values will be shown in the ruler:
Cursor position - to show the values of the cursor position in the ruler.
Selection - to show the values of the selection rectangle in the ruler.
Measurement - to show the values of the measurement in the ruler.
Reflect rotation - if checked, then ruler will reflect the screen or plotter rotation in the ruler also for length units. By default the screen or plotter rotation is reflected in ruler only for the the plotter logical units, i.e. for the plotter unit and for the HP-GL user unit.
No negative length values - if checked, then the length unit values will be always displayed as positive (i.e. their absolute values will be displayed).
Large size - select here the size of the ruler.
Large font - select here the font size of the ruler. The font sizes are maintained separately for small and large size of the ruler.
Serif font - if checked, a serif variant of the font will be used.
All the remaining items in the ruler menu serve for unit selection or definition:
Centimeter unit - the ruler unit is centimeter.
Millimeter unit - the ruler unit is millimeter.
Inch unit - the ruler unit is inch ( 1 inch = 2.54 cm ).
Custom unit - the ruler unit is some of the custom defined units.
Define/Select Custom unit - in this submenu you can either call a dialog to define a new custom defined unit or select some already defined custom unit.
Plotter unit - the ruler unit is plotter unit.
HP-GL User unit - the ruler unit is HP-GL user unit.