Ok I really really don't remember where I saw it. It's possible I saw it in a navigation program, or in Virtual Sailor. But I do remember it working in simple centimeters, but the maps having a clear scale of 5 cm (which on screen were more like 3-4 cm
) per 1,5,10,50,100 kilometers. The sides of the ruler were always there and it just got stretched out as you dragged the mouse. The length of the line was digitally printed but it didn't convert automatically to km, you had to do that yourself (a toggle option between cm and actual distances was available). The ruler itself did not create a line. You had to press the Shift key and click to create a line of that length, and the tool allowed you to continue by moving it's starting position to the last click. At the end it showed lengths for each segments and a total length for the entire line. You could move the text anywere along a segment and edit the text itself (converting manually to kilometers, for example). Right clicking reseted the tool.
And another small thing. In both SH3 and 4, everytime we click on an existing element, we modify that element. It's impossible to quickly make 2 lines that start from the same place. Can't you make a default "create mode" and make use the SHIFT click for the "change mode"?