misc issues ftom Jose at DaltonMaag

[HinTak]

General Information
W0022 Recommended table is missing
We expect kern table missing because we don’t keep it unless the client specifically ask for it. It is a table that stores ‘old-style’ kerning information, not class kerning. The class kerning we use is stored in the GPOS table.
hdmx and LTSH tables won't be present in fonts that don’t have hinting instructions on the horizontal (x) axis.

I would add that these are not defined as recommended tables in the OT Spec, so calling them recommended is inaccurate.

GSUB
W5300 The FeatureRecord tag is valid, but unregistered
We expect this warning whenever in the font we use features that are not recognised by Font Validator. FV understands that the tag is valid but it doesn’t know what it is because its database has not been updated to the latest list of features available.
Tags commonly claimed as not registered: ssXX (where XX is the number of the Stylistic Set)

OS/2
E2132 The version number is invalid

OS/2 table version 4 is a valid version number in the latest OTspec, so Font Validator should be able to recognize it as valid.
E2127 The table length does not match the expected length for this version
With our latest policy about vertical metrics, we use OS/2 table version 4. This is not recognised by FV and we expect errors that affect further tests on the table (Error code W0051).
E2135 The xAvgCharWidth field does not equal the calculated value
Font Validator doesn't know how to calculate this value for OS/2 table version 4, where the method for calculating it has been changed.
E2101 There are undefined bits set in fsSelection field
This error is related to the usage of Bit 7 in the fsSelection (useTypoMetrics), that in older versions of the table (v3 and below) was not in use and it was supposed to be set on 0. Since this is now supported, it should be something Font Validator should support and check correctly.

gasp
E1003 The version number is not 0
E1000 Some rangeGaspBehavior fields contain invalid flags
We always expect these two errors because Font Validator doesn’t recognize the new version of the gasp table which contains ClearType fields.

hhea
W1402 Descender should be greater than or equal to head.yMin
Prescribing how vertical metrics should be calculated shouldn't be part of what Font Validator does, since there a multiple strategies and they can change from project to project, making FV suggestions invalid. This comment is valid for any other warning that involve vertical metrics.

loca
W1701 Loca references a glyf entry which length is not a multiple of 4
E1703 Loca entry points outside the glyf range
This happens when the last glyph in the font doesn’t have outlines. It’s a minor issue and seems to have no importance nowadays, so perhaps it may be fine to get rid of it? To investigate.

maxp
W1900 The value doesn’t match the calculated value
I think for this one, the way the value is calculated by different tools varies. I add it just to encourage double-checking this against the OTspec. To investigate what the correct way to calculate this is.

[HinTak]

My initial responses:

support for v4 and v5 OS/2 table was added in Nov 10 2015
b99bf6e

correct OS/2 xAvgCharWidth calculation for v4/v5 tables - somebody else filed in Dec 2017
683f2e6