PS/PDF API Change Proposal: (Re: [cairo] Semantics of transparent objects)

[Michael Sweet]

Carl Worth wrote:
> On Wed, 18 Jan 2006 20:01:04 -0500, Michael Sweet wrote:
>> Carl Worth wrote:
>>> ...
>>> Obviously, there _are_ a lot of printing-specific options, settings,
>>> and metadata that users will need to provide. And the point has been
>>> made above that these need to be available on a per-page basis.
>>>
>>> I'm wondering if we can't just use cairo_t for these, and specify that
>>> the time to set them is before any drawing operation on any given
>>> page. That is, just after cairo_create or cairo_show_page, and before
>>> any of cairo_stroke, cairo_fill, cairo_paint, cairo_mask,
>>> cairo_show_text/glyphs on that page.
>> That would work.  IMHO, the only "required" per-page attributes are
>> the media attributes: media color (the color of the paper, not whether
>> the output is in color), page size, media source, media type, and
>> media weight.
> 
> What's not clear to me yet is what cairo is supposed to do with these
> options. From the recent discussion on the desktop_printing list[*]
> it's been made quite clear that applications should emit
> printer-independent PostScript and that that should be passed along
> with printer-specific options to CUPS.

True, however that doesn't prevent inclusion of per-page options, you
just need to do it a little differently using %%IncludeFeature...

> So, cairo fits in on the PostScript-generation side of things. And if
> it should then always be generating printer-independent PostScript
> then I don't see why it should see any printer-specific settings, (or
> even what it could do with them if it shouldn't put them into the
> PostScript output).

At the very least you may want a mix of page sizes...

> Or are all the attributes you describe above printer-independent? I
> don't know for sure what you mean by "media source" for example. Is
> that the printer's paper tray? If so, that's clearly printer-specific.

Right.  Maybe an example will help:

     %%Page: 1 1
     %%PageBoundingBox: 0 0 595 842
     %%BeginPageSetup
     %%IncludeFeature: *PageSize A4
     %%IncludeFeature: *InputSlot LargeCapacity
     %%IncludeFeature: *MediaType Glossy
     %%IncludeFeature: *MediaColor White
     %%EndPageSetup

The PageBoundingBox comment tells CUPS the bounding box of the page.
It is important to note that the coordinates are *integers*...

The IncludeFeature lines allow you to inject per-page options without
putting printer-specific PostScript commands in the file...  They
also make sure that the options are set in the right order...

-- 
______________________________________________________________________
Michael Sweet, Easy Software Products           mike at easysw dot com
Internet Printing and Publishing Software        http://www.easysw.com