On k, 2008-06-10 at 21:17 +0400, Alexandre Prokoudine wrote:

I believe, https://blueprints.launchpad.net/inkscape/+spec/real-units deals with this issue in some way. Any ideas?

Hi!

Im really pleased to see this draft caught your eyes!

This blueprint in draft right now, I have informations which didnt write it down yet. And I also believe that there are some faults in there (coordinate origins (inkscape vs. svg standard. all the two defines top-left corner as 0,0?).

So I want to collect more information to be really helpful for somebody who will actually implement this long standing request. (just search in bug database to the words "coordinate", "viewbox", "transform", "units" to get an idea how widespread is this problem).

My understanding in a nutshell:

1. svg standard requires all units to be in px. And the origin of the coordinate is at the top-left point. (mirrored upside-down, how mere mortals would imagine)

2. The correct solution would be to define 22mm as 22px unit in the svg document, and use viewbox which scales by factor "3.5433070866"

3. For coordinate flipping use svg tranform element.

In this way all the conversion inaccuracies just would go away.

I need to research if it is possible for somebody who want to mix multiple unit (mm, in, pt) without inaccuracies. So if the default unit would be mm (so there would be a root viewbox element), all the other units would have a transform element with a scaling factor. So for "in" this scaling factor would be "90/3.5433070866".

This feature would be really helpful for CAD-like use-cases.

For more CAD use-cases please visit either this wiki page: http://wiki.inkscape.org/wiki/index.php/CAD

Or Albert's summer of code blueprint here: http://wiki.inkscape.org/wiki/index.php/BlueprintGeometricAndTechDrawing

Best regards, Khiraly