[cairo] [Bug 90166] Add a way to specify units (in SVG output)

[Bill Spitzak]

I would put USER first as it appears to be the default value, making
it zero is a good idea to avoid confusion.


On Mon, Oct 16, 2017 at 7:16 AM, Antonio Ospite <ao2 at ao2.it> wrote:
> On Mon, 16 Oct 2017 18:32:10 +1030
> Adrian Johnson <ajohnson at redneon.com> wrote:
>
>> On 16/10/17 18:24, David Kastrup wrote:
>> > Frankly, this is not just the "SVG abbreviations".  It's TeX terminology
>> > as well as used in HTML/CSS.  Programmers will tend to know the two
>> > character abbreviations better than the long names (FONT_X ? For real?).
>> >
>> > This does not look like an actual improvement to me.  That it prompts a
>> > bikeshedding discussion should be proof enough that this makes things
>> > more rather than less arbitrary and harder rather than easier to guess.
>>
>> I'm open to suggestions.
>
> From the comments, it looks like leaving the original names for the
> units seems acceptable, they may not be the easiest for everyone but
> they are standard, simple and more consistent in form (except PERCENT,
> and USER, sure), and I tried to document their meaning in the API doc.
>
> About reordering the enum, I'd just like to point out that the
> current order is taken from the CSS spec itself, we don't have to
> necessarily follow it, but it was like that for some reason.
> That said, just tell me how you want the enum ordered and I'll follow.
>
> After we sort out the ordering doubt I will submit a v2 with a
> clearer documentation and a getter function.
>
> Finally, I think that allowing also relative units to be used in the
> final document is OK, AFAICS their are all valid for width and height,
> at least according to SVG schema from here:
> https://github.com/oreillymedia/HTMLBook/tree/master/schema/svg
>
> I can validate Cairo SVGs like this:
>
>   1. Get all the files from here:
>      https://github.com/ao2/HTMLBook/tree/svg-schema-add-version-attribute/schema/svg
>      The original schema from w3c does not work with xmllint, and it
>      does not seem to be _official_ anyways.
>
>   2. Run the test program in the bug report to create the svg files, and
>      then:
>      $ for file in svg_output_*.svg; do xmllint --noout --schema SVG.xsd "$file"; done
>
> Ciao,
>    Antonio
>
> --
> Antonio Ospite
> https://ao2.it
> https://twitter.com/ao2it
>
> A: Because it messes up the order in which people normally read text.
>    See http://en.wikipedia.org/wiki/Posting_style
> Q: Why is top-posting such a bad thing?
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