Add `-dgs-neverembed-fonts` option

Add `-dgs-never-embed-fonts` option

Issue 4992/6: Doc: add description of `-dgs-never-embed-fonts` option

  This commit adds description of `-dgs-never-embed-fonts` option.

Issue 4992/5: Add never-embed-font-list for `-dgs-load-fonts`

  When you use both `-dgs-never-embed-fonts` and `-dgs-load-fonts` options,
  Ghostscript never embed fonts except TrueType for PDF file output.

Issue 4992/4: Add never-embed-font-list for OpenType/CFF (OTF, OTC) fonts

  When you use `-dgs-never-embed-fonts` option,
  Ghostscript never embed OpenType/CFF (OTF and OTC) fonts
  for PDF file output.

Issue 4992/3: Add never-embed-font-list for Type 1 (PFA and PFB) fonts

  When you use `-dgs-never-embed-fonts` option,
  Ghostscript never embed Type 1 (PFA and PFB) fonts for PDF file output.

Issue 4992/2: Add `never-embed-font-list` and `/NeverEmbed`

  When the option `-dgs-never-embed-fonts` is enabled,
  `/NeverEmbed` distiller parameter from `never-embed-font-list` list
  is added to the outputting PostScript file.

  When Ghostscript converts from the PostScript file to PDF file,
  it never embed the fonts which are in the `never-embed-font-list`.

Issue 4992/1: Add `-dgs-never-embed-fonts` option

  For Ghostscript, never embed fonts.

[lemzwerg, 2016-10-28 17:50:21]

LGTM!

https://codereview.appspot.com/312970043/diff/1/Documentation/usage/running.i...
File Documentation/usage/running.itely (right):

https://codereview.appspot.com/312970043/diff/1/Documentation/usage/running.i...
Documentation/usage/running.itely:602: @tab Ghostscript never embed fonts except
TreuType.
I suggest the following text:

@tab Make Ghostscript embed only TrueType fonts and no other font format.

https://codereview.appspot.com/312970043/diff/1/scm/lily.scm
File scm/lily.scm (right):

https://codereview.appspot.com/312970043/diff/1/scm/lily.scm#newcode287
scm/lily.scm:287: "Ghostscript never embed fonts except TrueType.")
Ditto.

[trueroad, 2016-10-29 08:03:26]

Fix text

[trueroad, 2016-10-29 08:05:57]

Thank you for your reviewing.

https://codereview.appspot.com/312970043/diff/1/Documentation/usage/running.i...
File Documentation/usage/running.itely (right):

https://codereview.appspot.com/312970043/diff/1/Documentation/usage/running.i...
Documentation/usage/running.itely:602: @tab Ghostscript never embed fonts except
TreuType.
On 2016/10/28 17:50:20, lemzwerg wrote:
> I suggest the following text:
> 
> @tab Make Ghostscript embed only TrueType fonts and no other font format.

Done.

https://codereview.appspot.com/312970043/diff/1/scm/lily.scm
File scm/lily.scm (right):

https://codereview.appspot.com/312970043/diff/1/scm/lily.scm#newcode287
scm/lily.scm:287: "Ghostscript never embed fonts except TrueType.")
On 2016/10/28 17:50:21, lemzwerg wrote:
> Ditto.

Done.

[pkx166h, 2016-10-29 11:40:36]

While I don't have any technical contribution and I don't want to stop useful
functionality but I notice that the command contains the phrase 'never embed'
but the description says that it *does* embed fonts after all.

Also, the Tracker description contains much more information in it descriptively
than the doc entry :)

I am happy to help with the documentation if language is a difficulty to
describe, but fundamentally what is the purpose of tihs command and why, as a
user, would I want to use (and perhaps not to use it?).

Thanks

[lemzwerg, 2016-10-29 12:42:55]

> While I don't have any technical contribution and I don't want to stop useful
> functionality but I notice that the command contains the phrase 'never embed'
> but the description says that it *does* embed fonts after all.

The wording is tricky.  TrueType and OpenType fonts are not `normal' fonts on
the PostScript side; you can't address them directly, only by using Ghostscript
extensions.  So if you have PostScript code that says `never embed', it affects
only fonts that are PS resources – and both TTFs and OTFs are not.

> I am happy to help with the documentation if language is a difficulty to
> describe, but fundamentally what is the purpose of this command and why, as a
> user, would I want to use (and perhaps not to use it?).

I leave a detailed answer to Masamichi-san :-)

[trueroad, 2016-10-29 17:18:21]

> > I am happy to help with the documentation if language is a difficulty to
> > describe, but fundamentally what is the purpose of this command and why, as
a
> > user, would I want to use (and perhaps not to use it?).
> 
> I leave a detailed answer to Masamichi-san :-)

This option is very useful when `lilypond-book` invokes `lilypond` command.
You will not use it when you directly invoke `lilypond` command.

When you create a PDF document using `lilypond-book` you may include many
LilyPond snippets in the main PDF file. 
Each snippet intermediate file is a small PDF file which is generated by
`lilypond` command.
Each of the small PDF files use the same fonts, Emmentaler and TeX Gyre.

`lilypond-book` invokes `lilypond` command for generating each snippet
intermediate small PDF file.
Then, it invokes TeX (pdfTeX, XeTeX, LuaTex etc.) for generating main PDF which
includes the small PDF files.

If the small PDF files contain embedded font subsets (it is the default of
`lilypond`), the TeX system includes them as-is in the main PDF.
As a result, several subsets of the same font are embedded in the main PDF.
It is not possible to remove the duplicates since they are different subsets.
This vastly increases the size of the main PDF file.

On the other hand, if the small PDF files contain embedded full font sets (by
the LilyPond `--bigpdfs` option), the TeX system also includes all of them in
the main PDF.
This time, the main PDF contains duplicates of the same full sets of fonts.
Therefore, Ghostscript can remove the duplicates.
This may considerably reduce the main PDF-file's size.

Finally, if the small PDF files contain some fonts that are not embedded (by
this option `-dgs-neverembed-fonts`), the TeX system outputs the main PDF file
with some fonts missing.
In this case, Ghostscript can embed the necessary fonts.
It can significantly reduce the required disk size.

Unfortunately, the never embed method does not work fine for TrueType fonts.
http://lists.gnu.org/archive/html/lilypond-devel/2016-10/msg00080.html

So this option embeds TrueType fonts but does not embed Type 1 fonts and
OpenType/CFF fonts.

[dak, 2016-10-29 17:24:54]

On 2016/10/29 17:18:21, trueroad wrote:
>
> Finally, if the small PDF files contain some fonts that are not embedded (by
> this option `-dgs-neverembed-fonts`), the TeX system outputs the main PDF file
> with some fonts missing.
> In this case, Ghostscript can embed the necessary fonts.
> It can significantly reduce the required disk size.
> 
> Unfortunately, the never embed method does not work fine for TrueType fonts.
> http://lists.gnu.org/archive/html/lilypond-devel/2016-10/msg00080.html
> 
> So this option embeds TrueType fonts but does not embed Type 1 fonts and
> OpenType/CFF fonts.

I'll be quite glad if building the docs stops consuming 4GB of disk space.  I
just had another build failure because of running out of space.

[pwm, 2016-10-31 18:32:09]

For consistency and readability should there be a dash between "never" and
"embed"?  For example: 
-dgs-never-embed-fonts rather than  
-dgs-neverembed-fonts

[trueroad, 2016-11-01 12:07:29]

dash between "never" and "embed"

[trueroad, 2016-11-01 12:46:57]

On 2016/10/31 18:32:09, pwm wrote:
> For consistency and readability should there be a dash between "never" and
> "embed"?  For example: 
> -dgs-never-embed-fonts rather than  
> -dgs-neverembed-fonts

Thank you for reviewing.
I've uploaded Patch set 3.

[trueroad, 2016-11-04 11:51:04]

Fix PNG output

[trueroad, 2016-11-04 11:52:37]

On 2016/11/04 11:51:04, trueroad wrote:
> Fix PNG output

I've noticed that PNG output is broken.
So I've fixed it and uploaded Patch Set 4.

[trueroad, 2016-11-09 14:18:23]

I've pushed to staging.

commit 67861efa3ebcd7e7a2c4f482d7b6b94d6bf29f2c
Issue 4992/6: Doc: add description of `-dgs-never-embed-fonts` option

commit 25369cc54853cf02a42a723c19e4c0f70865677f
Issue 4992/5: Add never-embed-font-list for `-dgs-load-fonts`

commit db313ad3bc0e00e323b9f8f07852070b79d15096
Issue 4992/4: Add never-embed-font-list for OpenType/CFF (OTF, OTC) fonts

commit 507310b9197dba51c57a3a2de280c90d4f65d840
Issue 4992/3: Add never-embed-font-list for Type 1 (PFA and PFB) fonts

commit a27fbd6ec52f5ecf7adbe830599d0d831cc77f97
Issue 4992/2: Add `never-embed-font-list` and `/NeverEmbed`

commit 6471bbe9a2bc3cdfc43adbc1272e936f6521994a
Issue 4992/1: Add `-dgs-never-embed-fonts` option