Need instructions for updating custom document templates and extensions

[Hachmann]

On inkscapeforum.com, tylerdurden mentioned that his default template didn't seem to use the new dpi value. Turned out that it was a custom template (http://www.inkscapeforum.com/viewtopic.php?f=5&t=31553).

On the same forum, someone reported that the extension they made didn't work correctly with Inkscape 0.92 (http://www.inkscapeforum.com/viewtopic.php?t=31525)

I think we need some simple instructions for these cases, that can be added to the release notes or as a tutorial to the website.

I don't know enough to compose it myself, but I'll be happy to copyedit and put it where people can find it.

[Pelle Nilsson (lifelike)]

I was the one that had problems with extensions not working properly in 0.92. I asked a Question here on launchpad a few days ago also asking for some clarification on how an extension is expected to properly parse and generate SVG to work properly with user-units for different versions of Inkscape used to create the document or run the extension.

https://answers.launchpad.net/inkscape/+question/431543

[Hachmann (marenhachmann)]

Pelle, I've subscribed you to this report (this doesn't happen automatically). I hope that was okay :)

[su_v (suv-lp)]

@Pelle - re «extensions handling user-units and query-all in 0.92», this is probably bug #1508400, now tracked in bug #1525418.

[Pelle Nilsson (lifelike)]

Thanks! So it has been known for over a year and I need to learn to search better.

I will have a look at the extensions mentioned as doing their own viewBox calculations and see if something similar (or copies of their code) will also work as a workaround for my extension.

[su_v (suv-lp)]

@Pelle - the extension 'Visualize > Measure' AFAICT is one of the bundled extensions which does support arbitrary document scale:
https://bazaar.launchpad.net/~inkscape.dev/inkscape/0.92.x/view/15320/share/extensions/measure.py#L214
measure.py does not rely on methods from inkex.py to determine the document scale stored in the 'factor' variable (page dimension / viewBox dimension) - not an ideal solution either, IMvHO. Personally, I still think that the unit conversion methods provided for the Effect() class in inkex.py should support arbitrary document scales, even if I retracted my originally proposed implementation (the issue is not solved).

The code as originally proposed for (closed) bug #1508400 is still in use for example in these custom, externally hosted extensions:
* https://gitlab.com/su-v/inx-exportcoords
* https://gitlab.com/su-v/inx-exportobjects
They have a compatibility class for Effect() with a new get_document_scale() method, which is used by overloaded unittouu() and uutounit() methods. The code called by get_document_scale() is rather dated, and I probably would change parts of it based on what I have learned since.