Closed shapes with mix of curves and straights are messed up by DXF exporter

[Steve Baker]

If I create a closed shape in Inkscape with a mix of curved and straight lines - then SaveAs DXF, the resulting shape contains additional lines that should not be present in the output.

I've attached an example of a file that fails. When you export as DXF (with default settings), you get an additional horizontal line cutting across the "tabs" along the bottom edge of the left-hand shape and the top edge of the right-hand shape. Since I'm using this for laser-cutting, the result is a disaster!

Unchecking the "use LWPOLYLINE type of line output" option (which is checked by default) seems to work around the bug.

I'm not a DXF expert and I'm not familiar with Inkscape internals - but what I *SUSPECT* is happening is this:

* SVG supports both curved lines and straight lines within
  the same underlying structure...and it knows when a shape
  is "closed" or "open".

* DXF has DIFFERENT underlying structures for splines,
  straight lines and collections-of-straight-lines (POLYLINES).

* So the DXF exporter breaks apart SVG shapes into curves and
  straight lines and puts them into different DXF structures.

* When "use LWPOLYLINE" is selected, the exporter seems to collect
  all of the straight lines into one DXF structure...a polyline.
  Otherwise each line goes into a separate DXF object.

* What it SHOULD do is to realize that in breaking up a
  single SVG shape into multiple DXF shapes, it has to convert
  from a "closed" shape into several "open" shapes.

* It looks like LWPOLYLINE option incorrectly sets the
  resulting polyline shape to "closed" - when in fact it's now
  "open" because we removed the curves from the original SVG shape.

If my guess is right then this should be an easy fix - but if not, then someone should remove the "use LWPOLYLINE" option until the bug can be properly tracked down and fixed.

Thanks guys! Inkscape rocks! You do a great job.

[Steve Baker (y9a7s7tjd2-s1eac-si9yrl01qs)]

Here is the broken DXF file generated by exporting the SVG file that's attached to the bug report with default export options.

[Alvin Penner (apenner)]

- not reproduced on Windows 10, Inkscape 0.92.1 r15371
- you may need to upgrade to a newer version of Inkscape, or just upgrade the dxf output routine by itself.
- you can get a recent version of the files dxf_outlines.py, and dxf_outlines.inx, and inkex.py from:

http://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/files/head:/share/extensions/

if you decide to use a newer version, you will need to be aware of the fact that current Inkscape uses a default resolution of 96 dpi while previous versions used 90 dpi as the default.

[Steve Baker (y9a7s7tjd2-s1eac-si9yrl01qs)]

Yeah - I agree, it seems to be fixed in 0.92.1 - regardless of whether you check the use LWPOLYLINE flag is set.

Many thanks!

[Alvin Penner (apenner)]

good to hear, in that case I'll mark this as fixed