Comment 10 for bug 611907

> The term quadrant is a poor choice. It bears no relation to the
> x-y axis of the plot (true Cartesian coordinate system
> quadrants), but is basically internal angles from zero to pi/2
> or interior angles from pi/2+ to 2pi. It does not matter in
> which Cartesian quadrant the arc starts or finishes but whether
> the included angle would span one or multiple quadrants if the
> centre was placed at the origin and the start on an axis.

A reference I have seen would seem to contradict this.

http://www.rulabinsky.com/cavd/text/chapa.html

Section A.3

In this he gives an example of drawing an arc, centered at 0,0, starting at -4,3 and going to 3,4 and states that it must be split up into 2 arcs, one going from -4,3 to 0,5 and one from 0,5 to 3,4

Also, at http://www.ams-us.com/princi.html the description of G74 versus G75 seems to imply this.

Here is a quote:

"Another important case for G codes is when determining if the arc is a quadrant (G74) or Full 360 (G75). Quadrant arcs never cross quadrant boundaries, because the center co-ordinate offsets (I,J Codes) are always unsigned (even if they are negative!). Therefore, it requires at least four G74 arcs to draw one complete circle.

center co-ordinate offsets for 360 arcs (G75) can be positive or negative, allowing for a single command to draw a complete circle.

In either case, the center co-ordinates are given relative to the start point of the arc. The most dramatic difference between Quadrant and Full 360 arcs is that a Quadrant arc with identical start and end points has a sweep of 0 degrees, whereas a similar Full 360 arc is a full circle."