SVG rendering incorrect for a path with multiple simple subpaths.

[DavidPhillipOster]

The python qrcode package pyqrcode generates SVG using a series of short horizontal and vertical line segments.

Example of creating the .svg attached.

import pyqrcode
from pyqrcode import QRCode
getqrcode = pyqrcode.create("A")
getqrcode.svg("qrA.svg", scale=1)

OpenSCAD version 2021.01, given the following .scad file:

import("qrA.svg");

does not parse this correctly compared to Inkscape and Google Chrome. qrA.svg could be worked up into a unit test.

Originally posted by @DavidPhillipOster in #1740 (comment)

but reduced to a smaller file, with expected and actual results.

the SVG file

qrA.svg renamed so I can attach it here: qrA_svg.txt

Expected results

qrA.svg as rendered by Chrome and Inkscape

Actual results

as rendered by OpenSCAD version 2021.01

The problem is most visible in the corners - what should be a square surrounded by a larger square is merged into a single shape.

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[MichaelAtOz]

Note that QR codes seem to frequently contain points which become non-manifold.
e.g. http://forum.openscad.org/Preview-OK-Render-gets-only-half-tp33306p33315.html
That won't be the cause of the above issue, but could be your next problem.
As shown, offset() is a work-around.

[DavidPhillipOster]

Thank you. Yes:

linear_extrude(1)offset(0.001)import("qrA.svg");

reports as valid. Without the offset() I get:

ERROR: The given mesh is not closed! Unable to convert to CGAL_Nef_Polyhedron. 

But the rendering is still badly wrong: the shapes look nothing like they are supposed to.

To anyone in the future reading this: Python's pyqrcode can generate .png files just a well as .svg and I'd expect that OpenSCAD would have no trouble with a .png barcode.