Re: Help with print encoding

On 14/02/2017 20:32, Lifepillar wrote:
> On 14/02/2017 16:43, Mike Williams wrote:
>> On 14/02/2017 07:25, Lifepillar wrote:
>>> On 13/02/2017 18:08, Mike Williams wrote:
>>>> The reason you see the upside-down question marks is because VIM
>>>> converts the buffer content from utf-8 to latin1, but the latin1
>>>> character set does not include the left and right single quotes and VIM
>>>> will change them to upside-down quotes so they stand out. On Macs there
>>>> is special code to convert utf-8 to Mac encoding where the left and
>>>> right quotes exist, so that should work for you. Unfortunately I don't
>>>> have access to a Mac to confirm this.
>>>
>>> I do not know much about print encondings, but... wouldn't it be
>>> possible to define new print encodings, namely a UTF-8 print encoding?
>>
>> That would make life easier, but history is against you I'm afraid.
>
> Would you care to elaborate? Is PostScript the problem? If so, can Vim
> bypass generating a PostScript file?

Almost all printing technology pre-dates Unicode and earlier unified
character set technology. Early products would be sales region specific
- for example Western printers would not print East Asian text and vice
versa (OK they did ASCII but not the wider European character set, but I
digress).

The early printers were very limited in processing power and available
memory. The original methods of font definition and use were organised
around minimising font sizes and a lot of the print file text encoding
methods were designed to support this. They provide some internal fonts
but because of font licensing and hardware constraints there were only a
few fonts covering the basic design styles - fixed width, serif,
sans-serif, and symbols.

This means if you wanted to use any other fonts on the printer they have
to be downloaded to the printer. These fonts could be large, and if you
use multiple fonts your print file size balloons, and then your printer
runs out of memory and fails to print. Techniques developed to reduce
the final file size to help printing these complex files, but they were
not trivial.

VIM printing support was added in the late 90s. It uses four fonts
(each of the Courier normal, bold, italic and bold-italic variations are
distinct fonts) which are all provided by default in PostScript printing
systems. Importantly this also means that everything is known about the
fonts (glyph sizes, complement, etc.).

Most printing technology in use today (PS, PDF, XPS) supports fonts with
a large number of glyphs, and multi-byte character encodings (including
various Unicode encodings) for the text to be printed. It would be
possible to add support to VIM given time - it would need to include a
font reader, font rewriter (to avoid including a few megabytes of font
data not needed), four fonts to be used for the four styles (although it
could implement a poor man's version for bold and italic versions) which
are suitably licensed for inclusion with VIM. Adding support for
arbitrary fonts provided by the user raises the bar further due to the
various font formats available and varying glyph complements. And you
still have the issue of what to do if a font does not contain the glyph
for the character you want printed.

At the end of the day VIM is a text editor. It supports basic printing
with limited styling - it is not a full Unicode scripting engine with
printing. Generally text files are written in a single well defined
script, or character set, which can normally be handled by an 8-bit
encoding (there is support for CJK MBCS printing as well). The
immediate problem is handling the transcoding of Unicode to a suitable
single byte character set. There are two possible solutions, selection
of single byte character set based on glyphs to be printed, or use
Unicode character alternates when transcoding to a character set. For
example converting your left and right quotes to apostrophes. I will be
suggesting the latter one to start with to the dev team.

Basically yes it could be done, but the amount of work and additions to
VIM seems out of proportion to the benefit gained. Some may say they
would love a full Unicode print support, possibly even with proportional
fonts but they their will be issues with composing characters and
possibly a layout-engine. These are far from trivial to implement and
most VIM users would have other priorities.

I hope that helps understand some of the issues to do with printing
these days.

TTFN

Mike
--
Where there's smoke, there's toast.

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