Add `-dfont-ps-resdir` option to embed fonts to PDFs later

Add `-dfont-ps-resdir` option to embed fonts to PDFs later

A similar purpose option, `-dfont-export-dir` exports fonts
as individual PostScript files for font embedding later.
However it cannot embed CID fonts to PDFs with Ghostscript 9.26 and later.

This `-dfont-ps-resdir` option creates
a subset of PostScript resource directory
in the directory specified by the option.
The directory contains symbolic links to font files
that Ghostscript can use to embed the fonts to PDFs later.
This method can embed CID fonts, even with Ghostscript 9.26 and later.

This `-dfont-ps-resdir` option skips TrueType fonts
because garbled characters occur same as `-dfont-export-dir` option.
Unlike `-dfont-export-dir` option,
it skips OTC (OpenType Collection/CFF) font files
because Ghostscript cannot handle them directly.

Simple usage:

```
$ lilypond -dfont-ps-resdir=resdir -dgs-never-embed-fonts foo.ly
$ gs -q -dBATCH -dNOPAUSE -sDEVICE=pdfwrite \
     -I resdir -I resdir/Font \
     -sOutputFile=foo.embedded.pdf foo.pdf
```

Note:
It is better not to specify the directory
that contains the name `Resource` because it has a special meaning
when specified with the -I option for Ghostscript.

[lemzwerg, 2020-04-28 15:51:33]

Very nice, thanks!

There are some grammar glitches in the documentation – I hope that a native
English speaker can improve that.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
File Documentation/usage/running.itely (right):

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:652: This is useful when you want to create a
font-non-embedded PDFs first
Replace this and the next line with

This is useful if you want to create PDFs without embedded fonts first, letting
Ghostscript embed the fonts in a follow-up step as shown below.

https://codereview.appspot.com/577900043/diff/577910043/scm/framework-ps.scm
File scm/framework-ps.scm (right):

https://codereview.appspot.com/577900043/diff/577910043/scm/framework-ps.scm#...
scm/framework-ps.scm:291: (ly:warning (_ "Font ~a cannot be used in PostScript
resource directory because it is an OpenType/CFF Collection (OTC) font.") name))
Please fold lines longer than 80 characters.

[Trevor Daniels, 2020-04-28 17:37:01]

Please read my suggested changes carefully and amend, as I've no knowledge of
the subject matter.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
File Documentation/usage/running.itely (right):

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:662: Note: Unlikely @code{font-ps-resdir},
Unlike ...

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:668: because embedding TrueType fonts later
cause garbled characters.
... causes ...

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:670: @code{gs-never-embed-fonts} embeds
TrueType fonts despite its name.
To avoid garbling characters, use
@code{gs-never-embed-fonts}, as this embeds TrueType fonts
despite its name.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:679: and then embed the fonts with Ghostscript
as shown below.
@item @code{font-ps-resdir} = @var{directory}
Set @var{directory} to build a subset of the PostScript resource directory to be
used for embedding fonts later.
This is useful when you want to create a PDF without embedded
fonts first and later embed the fonts with Ghostscript as shown below.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:694: Note: Unlikely @code{font-export-dir},
Unlike ...

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:702: @code{gs-never-embed-fonts} embeds
TrueType fonts despite its name.
See corresponding change above.

[trueroad, 2020-04-29 04:01:22]

Fix 80 characters and document

[trueroad, 2020-04-29 04:12:01]

Thank you for your reviewing.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
File Documentation/usage/running.itely (right):

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:652: This is useful when you want to create a
font-non-embedded PDFs first
On 2020/04/28 15:51:33, lemzwerg wrote:
> Replace this and the next line with
> 
> This is useful if you want to create PDFs without embedded fonts first,
letting
> Ghostscript embed the fonts in a follow-up step as shown below.

I used the sentence Trevor suggested below.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:662: Note: Unlikely @code{font-ps-resdir},
On 2020/04/28 17:37:01, Trevor Daniels wrote:
> Unlike ...

Done.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:668: because embedding TrueType fonts later
cause garbled characters.
On 2020/04/28 17:37:01, Trevor Daniels wrote:
> ... causes ...

Done.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:670: @code{gs-never-embed-fonts} embeds
TrueType fonts despite its name.
On 2020/04/28 17:37:00, Trevor Daniels wrote:
> To avoid garbling characters, use
> @code{gs-never-embed-fonts}, as this embeds TrueType fonts
> despite its name.

Done.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:679: and then embed the fonts with Ghostscript
as shown below.
On 2020/04/28 17:37:01, Trevor Daniels wrote:
> @item @code{font-ps-resdir} = @var{directory}
> Set @var{directory} to build a subset of the PostScript resource directory to
be
> used for embedding fonts later.
> This is useful when you want to create a PDF without embedded
> fonts first and later embed the fonts with Ghostscript as shown below.

I'd like to use @var{string} instead of @var{directory}, so I propose this
sentence.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:694: Note: Unlikely @code{font-export-dir},
On 2020/04/28 17:37:01, Trevor Daniels wrote:
> Unlike ...

Done.

https://codereview.appspot.com/577900043/diff/577910043/Documentation/usage/r...
Documentation/usage/running.itely:702: @code{gs-never-embed-fonts} embeds
TrueType fonts despite its name.
On 2020/04/28 17:37:01, Trevor Daniels wrote:
> See corresponding change above.

Done.

https://codereview.appspot.com/577900043/diff/577910043/scm/framework-ps.scm
File scm/framework-ps.scm (right):

https://codereview.appspot.com/577900043/diff/577910043/scm/framework-ps.scm#...
scm/framework-ps.scm:291: (ly:warning (_ "Font ~a cannot be used in PostScript
resource directory because it is an OpenType/CFF Collection (OTC) font.") name))
On 2020/04/28 15:51:33, lemzwerg wrote:
> Please fold lines longer than 80 characters.

Done.

[trueroad, 2020-05-02 09:55:23]

I've pushed to staging.

commit 2ff485fd858d55263ca46db431793943f8c993f1
Date:   Mon Apr 27 23:52:53 2020 +0900

Issue5947/2: Doc: Add `-dfont-ps-resdir` option to running.itely

commit 3ada4bbab00f1ad91bbf78ab4c63324b4e539d10
Date:   Mon Apr 27 23:52:33 2020 +0900

Issue5947/1: Add `-dfont-ps-resdir` option to embed fonts to PDFs later