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

[David Kastrup]

Adrian Johnson <ajohnson at redneon.com> writes:

> On 16/10/17 07:42, Petr Kobalíček wrote:
>> 'MM/CM' vs 'INCHES' and all others seems inconsistent to me.
>
> What do you suggest?
>
>> 
>> On Thu, Oct 12, 2017 at 9:38 PM, Adrian Johnson <ajohnson at redneon.com
>> <mailto:ajohnson at redneon.com>> wrote:
>> 
>>     On 12/10/17 21:59, Adrian Johnson wrote:
>>     > On 12/10/17 20:55, Antonio Ospite wrote:
>>     >> The API addition I originally proposed[1,2] looks like this:
>>     >>
>>     >> void cairo_svg_surface_set_document_unit (cairo_surface_t*,
>>     >> cairo_svg_unit_t)
>>     >>
>>     >> Where cairo_svg_unit_t is an enum type representing all the possible
>>     >> units.
>>     >
>>     > The enum in the patch is:
>>     >
>>     > typedef enum _cairo_svg_unit {
>>     >     CAIRO_SVG_UNIT_EM,
>>     >     CAIRO_SVG_UNIT_EX,
>>     >     CAIRO_SVG_UNIT_PX,
>>     >     CAIRO_SVG_UNIT_IN,
>>     >     CAIRO_SVG_UNIT_CM,
>>     >     CAIRO_SVG_UNIT_MM,
>>     >     CAIRO_SVG_UNIT_PT,
>>     >     CAIRO_SVG_UNIT_PC,
>>     >     CAIRO_SVG_UNIT_PERCENT,
>>     >     CAIRO_SVG_UNIT_USER
>>     > } cairo_svg_unit_t;
>> 
>>     We don't have to use the SVG abbreviations in the enum. The non standard
>>     abbreviations can be expanded to make it clearer. I've reordered it
>>     slightly to put the default first followed by the more common units.
>> 
>>     typedef enum _cairo_svg_unit {
>>         CAIRO_SVG_UNIT_POINTS,
>>         CAIRO_SVG_UNIT_PIXELS,
>>         CAIRO_SVG_UNIT_MM,
>>         CAIRO_SVG_UNIT_CM,
>>         CAIRO_SVG_UNIT_INCHES,
>>         CAIRO_SVG_UNIT_PICAS,
>>         CAIRO_SVG_UNIT_FONT_EM,
>>         CAIRO_SVG_UNIT_FONT_X,
>>         CAIRO_SVG_UNIT_PERCENT,
>>         CAIRO_SVG_UNIT_USER
>>     } cairo_svg_unit_t;

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.

-- 
David Kastrup