1381775 - Kerning issues with CSS-imported TTF and WOFF fonts

Status: RESOLVED INVALID

(Core :: Layout: Text and Fonts, defect)

Description

[khorrth]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:54.0) Gecko/20100101 Firefox/54.0
Build ID: 20170630112252

Steps to reproduce:

I have developed a font with metrics based on pixel grid to be pixel-perfect. I have saved it in 3 different formats - TTF, OTF, WOFF. Then I have imported it using @font-face.


Actual results:

OTF and WOFF fonts rendered with no kerning, TTF was rendered a bit blurry. 
I have a testcase: http://khorrth.me/axb.html


Expected results:

OTF and WOFF fonts should be rendered with kerning at least. It is desirable TTF fonts to have such a good antialiasing like OTF ones.

Comment 1

[Jonathan Kew [:jfkthame]]

(In reply to khorrth from comment #0)
> OTF and WOFF fonts rendered with no kerning,

See https://www.microsoft.com/typography/otspec/kern.htm:

"OpenType™ fonts containing CFF outlines are not supported by the 'kern' table and must use the 'GPOS' OpenType Layout table."

So you need to convert your old-style 'kern' table to a GPOS 'kern' feature in order for it to work with the CFF font.

Comment 2

[khorrth]

(In reply to Jonathan Kew (:jfkthame) from comment #1)
> (In reply to khorrth from comment #0)
> > OTF and WOFF fonts rendered with no kerning,
> 
> See https://www.microsoft.com/typography/otspec/kern.htm:
> 
> "OpenType™ fonts containing CFF outlines are not supported by the 'kern'
> table and must use the 'GPOS' OpenType Layout table."
> 
> So you need to convert your old-style 'kern' table to a GPOS 'kern' feature
> in order for it to work with the CFF font.

The same font works fine if it is not imported by CSS, but available system-wide. I have a bit more detailed overview here: http://khorrth.me/ax.html

Is this normal behavior?

Comment 3

[khorrth]

(In reply to khorrth from comment #2)
> (In reply to Jonathan Kew (:jfkthame) from comment #1)
> > (In reply to khorrth from comment #0)
> > > OTF and WOFF fonts rendered with no kerning,
> > 
> > See https://www.microsoft.com/typography/otspec/kern.htm:
> > 
> > "OpenType™ fonts containing CFF outlines are not supported by the 'kern'
> > table and must use the 'GPOS' OpenType Layout table."
> > 
> > So you need to convert your old-style 'kern' table to a GPOS 'kern' feature
> > in order for it to work with the CFF font.
> 
> The same font works fine if it is not imported by CSS, but available
> system-wide. I have a bit more detailed overview here:
> http://khorrth.me/ax.html
> 
> Is this normal behavior?

And yeah, the GPOS is used.

Comment 4

[Jonathan Kew [:jfkthame]]

I downloaded the .otf and .ttf fonts linked from your testcase at http://khorrth.me/axb.html, and neither of them includes a 'GPOS' table; they only have the legacy 'kern' table:

$ ttx -l Wireshock-Regular-K.otf 
Listing table info for "Wireshock-Regular-K.otf":
    tag     checksum   length   offset
    ----  ----------  -------  -------
    CFF   0x34A84DA2     4587     1496
    FFTM  0x7FFB7A1E       28     6084
    OS/2  0x49955AE5       96      288
    cmap  0x9C1DC2EC      466      996
    head  0x0A317B03       54      188
    hhea  0x0022008E       36      244
    hmtx  0x04C10000      534     6112
    kern  0xE544FC68   104576     6648
    maxp  0x00865000        6      280
    name  0x165DD4E3      612      384
    post  0xFFFE0002       32     1464

$ ttx -l Wireshock-Regular-K.ttf
Listing table info for "Wireshock-Regular-K.ttf":
    tag     checksum   length   offset
    ----  ----------  -------  -------
    FFTM  0x7FFB7A1E       28   112288
    OS/2  0x49955AC5       96      344
    cmap  0xBE57E827      466      984
    gasp  0xFFFF0003        8   112280
    glyf  0xFEBCD7F8     5332     1728
    head  0x0A317B03       54      220
    hhea  0x00220090       36      276
    hmtx  0x04C80000      542      440
    kern  0x6D658488   104576     7060
    loca  0x55A7506E      274     1452
    maxp  0x00CD0017       32      312
    name  0x165DD4E3      612   111636
    post  0xFFFE0002       32   112248

Comment 5

[khorrth]

(In reply to Jonathan Kew (:jfkthame) from comment #4)
> I downloaded the .otf and .ttf fonts linked from your testcase at
> http://khorrth.me/axb.html, and neither of them includes a 'GPOS' table;
> they only have the legacy 'kern' table:
> 
> $ ttx -l Wireshock-Regular-K.otf 
> Listing table info for "Wireshock-Regular-K.otf":
>     tag     checksum   length   offset
>     ----  ----------  -------  -------
>     CFF   0x34A84DA2     4587     1496
>     FFTM  0x7FFB7A1E       28     6084
>     OS/2  0x49955AE5       96      288
>     cmap  0x9C1DC2EC      466      996
>     head  0x0A317B03       54      188
>     hhea  0x0022008E       36      244
>     hmtx  0x04C10000      534     6112
>     kern  0xE544FC68   104576     6648
>     maxp  0x00865000        6      280
>     name  0x165DD4E3      612      384
>     post  0xFFFE0002       32     1464
> 
> $ ttx -l Wireshock-Regular-K.ttf
> Listing table info for "Wireshock-Regular-K.ttf":
>     tag     checksum   length   offset
>     ----  ----------  -------  -------
>     FFTM  0x7FFB7A1E       28   112288
>     OS/2  0x49955AC5       96      344
>     cmap  0xBE57E827      466      984
>     gasp  0xFFFF0003        8   112280
>     glyf  0xFEBCD7F8     5332     1728
>     head  0x0A317B03       54      220
>     hhea  0x00220090       36      276
>     hmtx  0x04C80000      542      440
>     kern  0x6D658488   104576     7060
>     loca  0x55A7506E      274     1452
>     maxp  0x00CD0017       32      312
>     name  0x165DD4E3      612   111636
>     post  0xFFFE0002       32   112248

https://fontforge.github.io/TrueOpenTables.html

"kern	kerning	Provides kerning information for Apple's truetype fonts (and for older MS truetype fonts). In OpenType fonts this information is contained in the GPOS table."

So, the "kern" table is a subtable of GPOS. When I save with "old-style kern for Windows" option, it doesn't change anything.

Comment 6

[khorrth]

Oh, I am sorry. I was wrong about it, found the solution. Thank You.