gEDA-dev: Broken libgd support in gschem (arc drawing) PATCH

[Peter Clifton]

I've discovered that after enabling libgd, it draws the arcs upside-down
with respect to what gschem does.

It appears that libgd has angles starting with 0 degrees on the +ve X
axis (rightmost), and +ve clockwise.

gschem appears to have 0 degrees on the +ve X axis (rightmost), and +ve
ANTI-clockwise (which is more what an electrical engineer might
expect :))

The code before was obviously buggy - look at some of the "if"
statements - so I've re-written it. It appears to work in all cases I
tried.

libgd has a requirement that start_angle < end_angle, and draws
clockwise between the two. It doesn't like -ve angle inputs.

So.. for example, to draw between -10 and 10 degrees, spanning an arc of
20 degrees, you'd pass start_angle = 350 and end_angle = 370.

(I think it also works with start_angle = 350 and end_angle = 10 but the
manual does specifically say end_angle must be greater than start_angle)

*** If you want to wait on this bug, until after the noscreen work
merges - there is already a combined fix for this and noscreen in my
branch (git - not CVS yet) ***

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)
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