• com.google.fonts/check/ftxvalidator_is_available

--- Rationale ---

There's no reasonable (and legal) way to run the command `ftxvalidator` of the
Apple Font Tool Suite on a non-macOS machine. I.e. on GNU+Linux or Windows etc.

If Font Bakery is not running on an OSX machine, the machine running Font
Bakery could access `ftxvalidator` on OSX, e.g. via ssh or a remote procedure
call (rpc).

There's an ssh example implementation at:
https://github.com/googlefonts/fontbakery/blob/master/prebuilt/workarounds
/ftxvalidator/ssh-implementation/ftxvalidator

• ⚠ WARN Could not find ftxvalidator.

• com.google.fonts/check/name/license

--- Rationale ---

A known licensing description must be provided in the NameID 14 (LICENSE
DESCRIPTION) entries of the name table.

The source of truth for this check (to determine which license is in use) is a
file placed side-by-side to your font project including the licensing terms.

Depending on the chosen license, one of the following string snippets is
expected to be found on the NameID 13 (LICENSE DESCRIPTION) entries of the name
table:
- "This Font Software is licensed under the SIL Open Font License, Version 1.1.
This license is available with a FAQ at: https://scripts.sil.org/OFL"
- "Licensed under the Apache License, Version 2.0"
- "Licensed under the Ubuntu Font Licence 1.0."


Currently accepted licenses are Apache or Open Font License.
For a small set of legacy families the Ubuntu Font License may be acceptable as
well.

When in doubt, please choose OFL for new font projects.

• ⚠ WARN Please consider using HTTPS URLs at name table entry [plat=3, enc=1, name=13] [code: http-in-description]
• ⚠ WARN For now we're still accepting http URLs, but you should consider using https instead. [code: http]

• com.google.fonts/check/name/license_url

--- Rationale ---

A known license URL must be provided in the NameID 14 (LICENSE INFO URL) entry
of the name table.

The source of truth for this check is the licensing text found on the NameID 13
entry (LICENSE DESCRIPTION).

The string snippets used for detecting licensing terms are:
- "This Font Software is licensed under the SIL Open Font License, Version 1.1.
This license is available with a FAQ at: https://scripts.sil.org/OFL"
- "Licensed under the Apache License, Version 2.0"
- "Licensed under the Ubuntu Font Licence 1.0."


Currently accepted licenses are Apache or Open Font License.
For a small set of legacy families the Ubuntu Font License may be acceptable as
well.

When in doubt, please choose OFL for new font projects.

• ⚠ WARN Please consider using HTTPS URLs at name table entry [plat=3, enc=1, name=13] [code: http-in-description]
• ⚠ WARN Please consider using HTTPS URLs at name table entry [plat=3, enc=1, name=13] [code: http-in-description]
• ⚠ WARN Please consider using HTTPS URLs at name table entry [plat=3, enc=1, name=13] [code: http-in-description]
• ⚠ WARN For now we're still accepting http URLs, but you should consider using https instead. [code: http]

• com.google.fonts/check/metadata/listed_on_gfonts

• ⚠ WARN Family not found via Google Fonts API. [code: not-found]

• com.google.fonts/check/valid_glyphnames

--- Rationale ---

Microsoft's recommendations for OpenType Fonts states the following:

'NOTE: The PostScript glyph name must be no longer than 31 characters, include
only uppercase or lowercase English letters, European digits, the period or the
underscore, i.e. from the set [A-Za-z0-9_.] and should start with a letter,
except the special glyph name ".notdef" which starts with a period.'

https://docs.microsoft.com/en-us/typography/opentype/spec/recom#post-table


In practice, though, particularly in modern environments, glyph names can be as
long as 63 characters.
According to the "Adobe Glyph List Specification" available at:

https://github.com/adobe-type-tools/agl-specification

• ⚠ WARN The following glyph names may be too long for some legacy systems which may expect a maximum 31-char length limit: numbersign_underscore_parenleft.liga, asciitilde_asciitilde_greater.liga and less_dollar_greater.liga.BRACKET.600 [code: legacy-long-names]

• com.google.fonts/check/monospace

--- Rationale ---

There are various metadata in the OpenType spec to specify if a font is
monospaced or not. If the font is not truly monospaced, then no monospaced
metadata should be set (as sometimes they mistakenly are...)

Requirements for monospace fonts:

* post.isFixedPitch - "Set to 0 if the font is proportionally spaced, non-zero
if the font is not proportionally spaced (monospaced)"
  www.microsoft.com/typography/otspec/post.htm

* hhea.advanceWidthMax must be correct, meaning no glyph's width value is
greater.
  www.microsoft.com/typography/otspec/hhea.htm

* OS/2.panose.bProportion must be set to 9 (monospace). Spec says: "The PANOSE
definition contains ten digits each of which currently describes up to sixteen
variations. Windows uses bFamilyType, bSerifStyle and bProportion in the font
mapper to determine family type. It also uses bProportion to determine if the
font is monospaced."
  www.microsoft.com/typography/otspec/os2.htm#pan
  monotypecom-test.monotype.de/services/pan2

* OS/2.xAvgCharWidth must be set accurately.
  "OS/2.xAvgCharWidth is used when rendering monospaced fonts, at least by
Windows GDI"
  http://typedrawers.com/discussion/comment/15397/#Comment_15397

Also we should report an error for glyphs not of average width.

Please also note:
Thomas Phinney told us that a few years ago (as of December 2019), if you gave
a font a monospace flag in Panose, Microsoft Word would ignore the actual
advance widths and treat it as monospaced. Source:
https://typedrawers.com/discussion/comment/45140/#Comment_45140

• ⚠ WARN Font is monospaced but 38 glyphs (2.3413431916204557%) have a different width. You should check the widths of: ['uni0308', 'uni0307', 'gravecomb', 'acutecomb', 'uni030B', 'uni0302', 'uni030C', 'uni0306', 'uni030A', 'tildecomb', 'uni0304', 'hookabovecomb', 'uni0312', 'uni031B', 'dotbelowcomb', 'uni0326', 'uni0327', 'uni0328', 'uni0340', 'uni0341', 'uni0308.case', 'uni0307.case', 'gravecomb.case', 'acutecomb.case', 'uni030B.case', 'uni0302.case', 'uni030C.case', 'uni0306.case', 'uni030A.case', 'tildecomb.case', 'uni0304.case', 'hookabovecomb.case', 'uni031B.case', 'acutecomb.loclPLK', 'acutecomb.case.loclPLK', 'uni0342', 'brevecombcy', 'brevecombcy.case'] [code: mono-outliers]

• com.google.fonts/check/gpos_kerning_info

• ⚠ WARN GPOS table lacks kerning information. [code: lacks-kern-info]