Spacing with Font Roboto

Bob Tennent rdtennent at
Tue Dec 10 23:09:28 CET 2019

 >|On Tue, Dec 10, 2019 at 03:05:11PM -0500, Bob Tennent wrote:
 >|> I've tried to re-construct the roboto package using the TTF
 >|> set and it certainly seems that otftotfm has problems with
 >|> those fonts, which is presumably why I had converted to OTF.
 >|> But the TTF Roboto fonts also have em size 2048. Why do they
 >|> work better with luatex than the converted OTF fonts?
 >|The usual rule is that TrueType based fonts have a power of two,
 >|normally 1024 or 2048 because this is sometimes faster for TTF
 >|renderers. In contrast, OpenType/CCF (aka .otf) fonts are based on Type 1
 >|fonts which traditionally use em size 1000. I don't know exactly where
 >|it is coming from but even the Type 1 font specification said that it is
 >|"typical of a Type 1 font program and is highly recommended". Given that
 >|OpenType just combined existing formats, this is one of many places
 >|where slightly different behaviour is expected for CFF and TTF fonts.
 >|Given that Type 1 based fonts with other em size are quite unusual and
 >|sometimes not supported, LuaTeX just sets the value to 1000 and then
 >|manually fixes the appearance if a Type 1 based font with non-standard
 >|em size is found. This doesn't happen for TrueType fonts because there,
 >|2048 isn't unusual in any way. (Also I think for TTF fonts it is more
 >|common to have non-standard em sizes, so renderers are usually more
 >|robust there)
 >|For reference, this "feature" of LuaTeX is the "fix" for
 >|Anyway, would it be an option to keep the OTF fonts but "rescale" them
 >|to 1000 em size. I think that's the usual approach here. In fontforge,
 >|that can be done by just changing the em size. Then fontforge takes care
 >|to rescale everything so that no difference can be seen.

I can do that for a single font but for all 32 of the
fonts in the family, I'd need a script. I've asked on the
fontforge-users mail list:

Bob T.

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