|Subject:||Re: [ft-devel] Loading empty bitmap fails?|
|Date:||Sun, 6 Aug 2017 20:21:43 -0700|
>> Indeed. Can you give me pointers to the OpenType specification where
>> this situation is covered? Currently, I don't find it...
> I cannot, because as it happens nowhere it says that it is an error
> if a strike does not contain an image for a glyph. :-)
Good to hear the confirmation :-)
> Joking aside, from the spec's point of view, bitmaps always
> accompanied outline shapes. In that situation, a missing bitmap
> meant "use outline". With CBLT/CBDT color fonts, there is no
> outlines and it is expected that any needed shape be present in all
> strikes. I think it's a logical follow up that if a strike does not
> provide a bitmap for a glyph, that glyph has no drawing.
Mhmm. I would like to have this formalized. Let's have a closer look
at NotoColorEmoji.ttf. The `cmap' table references glyph index 3 for
character code 0x20 (ttx calls this glyph `space'). GID 3 is also
used in the `hmtx' and `vmtx' tables. However, it is missing in the
`CBDT' table, and there is no `loca' table either.
So the basic question is `what defines GID 3'? IMHO it is not
sufficient to have a `cmap' entry. Maybe accept it only if there is
no `loca' table but an `hmtx' or `vmtx' entry?
How do the Apple and MS rendering engines behave?
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