Better Ruler / Straight Line tool.

[GoogleCodeExporter]

As I am studying Physics, I need to draw diagrams and tables very often. 
Some things that would make it more comfortable woukd be: 

optional Snapping to certain angles or paper lines
drawing of three point lines for creating specific angles. 
Display of the angle's current degree while drawing for every line you are 
crossing.
Display of the actual line's lenght while drawing.
Pressing the pen button to finish the line, because if you have to lift the pen 
up for that like now, the endpoint will almost always shift a little bit.

Thank you for the great software!

Original issue reported on code.google.com by [email protected] on 15 Sep 2013 at 11:08