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On 18-Sep-2014 06:54, LucaDC wrote:
IMHO each file should adhere to the units related to the page format: A4 is expressed in mm, US Letter is expressed in inches, Icon 16x16 is in px and so on.
Tav wrote problems. I also need to understand the purpose of the 'inkscape:document-units' property.
There are two things going on.
1. Defining the size of the document in length units. For that, as Tav pointed out, we have the viewbox. For letter it could be:
<svg width="8.5in" height="11in" viewBox="0 0 816 1056">
After some consideration it seems to me that the viewbox coordinates should come out to 96dpi no matter what the physical length units are. Since they are not integers there is no reason to expand the "precision" by using extra digits, for instance "0 0 8160 10560". By always using 96dpi for the viewBox if the viewBox line was deleted nothing would change. (A viewBox is not really needed to specify the size of the drawing, if the viewBox uses 96 dpi, then it just tells the physical program the physical length units to use - for the same length.)
It would be natural for a letter sized document to be in inches, but there is no reason it could not be in mm, and there are probably applications where that would be useful. Changing from one to the other should be (but is not currently) as simple as changing that one line to:
<svg width="215.9mm" height="279.4mm" viewBox="0 0 816 1056">
and nothing else would need to change withing the document, since its "natural" unit would still be in use at 96dpi. This pixels to units conversion is used on export and import of data from the SVG file, including printing it and sending it to plotters.
2. Defining the length units for the GUI. This would affect what the user sees for cursor position, and any lengths, as in the rectangle drawing too. That would be set by:
inkscape:document-units
This should not affect the rest of the SVG document in any way. This is also broken in places, notably the rectangle drawing tool, which doesn't keep track of all the units/transforms.
Regards,
David Mathog mathog@...1176... Manager, Sequence Analysis Facility, Biology Division, Caltech