Sorry for the delay. I think I'm getting it :-)

Now, more or less understanding "user units", I'm back at #3 of your first reply. And here in the middle of that paragraph....I think....is the answer I need.

(temporarily set display unit to px, set scale

to 1, put display unit back to whatever you need),

So when someone needs to change the Display units, so that their drawing is as close to real world size as possible, do this:

1 -- set the desired Page Size and units (this sets the viewBox, right?) 2 -- temporarily change Display units to px 3 -- change the Scale to 1 4 -- change the Display units to the desired unit 5 -- the Scale will automatically change to the appropriate value 6 -- leave everything else alone

If that's correct then

1 -- I'll make a new FAQ item for it (if no objections) - perhaps link to Marc's article about it - or is there a wiki page for it? 2 -- I'm really thinking Inkscape needs to do all that internally. I think users should be able to simply select the unit they want, the page size they want, and Inkscape does the rest. May I make the bug/feature report, or is it already planned or requested?

If that's not correct, please tell me where I'm going wrong.

Oh, one last question.

If you only measure

your stuff with the display units (and do not use units in the code, it should not matter (tools "should" take the scale into account, and if some do not it's an bug

Do you mean to say that it's possible some tools are not respecting the Scale? Or is that more of a theory.

Thanks again, brynn

-----Original Message----- From: Marc Jeanmougin Sent: Friday, September 15, 2017 2:22 AM To: inkscape-user@lists.sourceforge.net Subject: Re: [Inkscape-user] the Scale setting and Display units

On 09/15/2017 10:00 AM, brynn wrote:

What is a "user unit" and what do you mean by "outside coordinate system"? Please don't explain anything below that unless you can't explain "user unit" and "outside coordinate system" otherwise. Hopefully once I understand those 2 things, the rest will make sense. But I need to go one step at a time.

The "outside coordinate system" is just the length of things upon displaying the file, assuming one respects the given "Size" of the document.

"Inside" the file, everything is measured with the "inside" coordinate system. This system's unit is the abstract "user unit": your document may have a rectangle measuring 2 user unit wide and 5 user units tall, and you can tell (in the viewBox) that your complete document is the area between the point of coord (0,0) and the point of coord (20,50), in user units.

They're abstract units, like when you do basic geometry in mathematics, without units; only meaning here that 2 user units wide is 10% of the document's width and 5user unit tall is 10% of the document's height. Only the additional data of the "Size" can tell you what the total height is in the "outside world", hence what 10% of it (== my 5uu of height) are worth.

Now, the units *inside* the file (like the "cm" in my post-scriptum) are only shortcuts for given, fixed, multiples of the user unit (by definition, "px" is the name of that user unit and "in" is the name given to 96 user units), but if you do not set "1 user unit is one outside-world-pixel", they're not worth what they seem.