Add support for layers in documents created with Draw.io

[ThinkBriK]

Hi !

It would be really cool to support SVG exported by Draw.io (I actually opened https://github.com/jgraph/drawio/issues/694 without success so far).

Currently draw.io exported SVG transform layers into groups which are not usable by Sozi.

• Which version of Sozi are you using : 19.04
• Which drawing software did you use : Draw.io 12.5.6
• On which platform : Fedora Linux 31 64-bit
• If your problem happens when playing a presentation, which browsers have you tried? Chromium 79.0.3945.117

[magicvince]

Same problem beetween Inkscape 1.01 and diagrams. The problem seems to be a bad svg export from draw.io/diagrams.net

I had notified this bug on novembre 2019 : [(https://github.com/jgraph/drawio-desktop/issues/184)]

[sagb]

How to change an arbitrary SVG group into format which Sozi interprets as layer? I've tried to emulate inkscape's

<g   inkscape:groupmode="layer"   id="layer2"   inkscape:label="2nd part"

to no avail. What's missing here?

[aumouvantsillage]

@sagb Have you added the inkscape namespace to your document?

<svg
    ...
    xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
    ...