printing circles and arcs is broken

[westram]

Status:

1. clipping does not work:
   currently there's a hack in print-code, which does a box-clip and then
   • either prints a smaller circle/arc if more than 50% of surface is visible or
   • complete skips the circle/arc
2. drawing partial arcs doesn't work properly (position/size is wrong; probably world/screen-coordinate confusion)
3. drawing arcs with x-radius==0 or y-radius==0 fails assertions

Todo:

1. clipping has to calculate the arc-segments remaining inside visible region and draw each segment separately
2. fix
3. shall fallback to line or dot

[westram]

Replying to description:

2. drawing partial arcs doesn't work properly (position/size is wrong; probably world/screen-coordinate confusion)

Works for secondary structure (bond for character '~' uses arc).

See attachments for example of .

[westram]

patch vs trunk @ 15376 (code discarded during impl. of #578)

[westram]

broken output