Nothing gets drawn on screen except for bounding boxes after importing a DXF file

[Yegor]

If I import this particular DXF, the drawing area becomes blank. This includes objects that are visible prior to importing the file. Changing the display mode, zooming in/out doesn't help. Saving to SVG and re-opening doesn't help either. Bounding boxes, guides and other non-payload stuff are all visible and can be acted upon, but the image itself is blank. It does render on export though.

Steps to take:
1. Start new Inkscape instance.
2. Draw something, a couple shapes will do.
3. Drag the DXF file into the drawing area to import it.
4. Observe the bug.
5. Export the drawing to a PNG file - the image will be there.

The DXF file was generated by Ascon Kompas 3D V13.

Windows 10 64-bit, Inkscape 0.91 r13725

[su_v (suv-lp)]

DXF import with Inkscape 0.91 creates text objects with font size 0px:
  style="font-size: 0.0px;
which triggers a known regression in Inkscape 0.91:
* Bug #1294784 “text with font of size zero pixels renders drawing invisible (rev >= 12488)”
  https://bugs.launchpad.net/inkscape/+bug/1294784

[su_v (suv-lp)]

Font size '0px' reproduced on DXF import of the test case with Inkscape 0.91 r13725 and 0.91+devel r14430 on OS X 10.7.5.

The text renders visible in other DXF viewers/editors, so possibly DXF import could be improved to extract and assign the correct font size. Using "UTF 8" as character encoding for import works ok for the content of the text objects and layer names, but does not help wrt font size.

[Alvin Penner (apenner)]

attached is a proposed modification of the file dxf_input.py. It will ignore the font size if it is zero, and will use a default value instead. This will make the file file.dxf visible.

[Alvin Penner (apenner)]

committed to rev 14437

[su_v (suv-lp)]

Fix backported to 0.91.x in rev 13847.