* [NTG-context] OpenType contextual alternates disabled by default
@ 2025-09-09 7:34 Max Chernoff via ntg-context
2025-09-09 7:59 ` [NTG-context] " Hans Hagen via ntg-context
0 siblings, 1 reply; 4+ messages in thread
From: Max Chernoff via ntg-context @ 2025-09-09 7:34 UTC (permalink / raw)
To: ntg-context; +Cc: Max Chernoff
Hi Hans,
OpenType contextual alternates ("calt") seem to be disabled by default
in ConTeXt. However, the OpenType spec recommends that this is enabled
by default
https://learn.microsoft.com/en-us/typography/opentype/spec/features_ae#tag-calt
and it's enabled by default in both HTML and HarfBuzz
https://drafts.csswg.org/css-fonts/#default-features
https://harfbuzz.github.io/shaping-opentype-features.html
Changing this default in ConTeXt probably isn't possible due to
backwards compatibility concerns, so this is more of an FYI than a
request for any changes to be made.
Background: this came up in a recent TeX.SE question
https://tex.stackexchange.com/a/750767
where a new user was surprised by ConTeXt's default setting since it
makes some fonts render differently than other programs.
Thanks,
-- Max
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^ permalink raw reply [flat|nested] 4+ messages in thread* [NTG-context] Re: OpenType contextual alternates disabled by default 2025-09-09 7:34 [NTG-context] OpenType contextual alternates disabled by default Max Chernoff via ntg-context @ 2025-09-09 7:59 ` Hans Hagen via ntg-context 2025-09-09 20:16 ` Wolfgang Schuster 0 siblings, 1 reply; 4+ messages in thread From: Hans Hagen via ntg-context @ 2025-09-09 7:59 UTC (permalink / raw) To: ntg-context; +Cc: Hans Hagen On 9/9/2025 9:34 AM, Max Chernoff via ntg-context wrote: > Hi Hans, > > OpenType contextual alternates ("calt") seem to be disabled by default > in ConTeXt. However, the OpenType spec recommends that this is enabled > by default > > https://learn.microsoft.com/en-us/typography/opentype/spec/features_ae#tag-calt > > and it's enabled by default in both HTML and HarfBuzz > > https://drafts.csswg.org/css-fonts/#default-features > > https://harfbuzz.github.io/shaping-opentype-features.html > > Changing this default in ConTeXt probably isn't possible due to > backwards compatibility concerns, so this is more of an FYI than a > request for any changes to be made. > > Background: this came up in a recent TeX.SE question > > https://tex.stackexchange.com/a/750767 > > where a new user was surprised by ConTeXt's default setting since it > makes some fonts render differently than other programs. We started with opentype support (2005) when there wasn't much info about it. The reference implementation was uniscribe so we had to guess and compare with that. The xetex engine was using some libraries and changed them later on. So we couldn't check that out either. Now, when it comes to features, those experiences, also with specific fonts, made us decide for the defaults. Over time the specification became better and more complete but as you say: we want to remain compatibility. (I assume that ltx folk spend substantial time on checking changes in hb every time there is an update in tex live, which is quite often if i look at git syncing.) An omission in otf is that the font doesn't specify what features are to be on by default. Combine that with font usage where users have no control over features, and we see why soem are just turned on. Probably the same for some (fixing) heuristics. It's now how tex works: there we *ask* for something, not being *enforced* to. If I could motivate myself we could of course make such a list of default features per font. Of course one can wonder why we have rlig/lig/clig as well as kern/dist split into several features when they are supposed to be always on. But I will not waste time on pondering that. Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl ----------------------------------------------------------------- ___________________________________________________________________________________ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / https://mailman.ntg.nl/mailman3/lists/ntg-context.ntg.nl webpage : https://www.pragma-ade.nl / https://context.aanhet.net (mirror) archive : https://github.com/contextgarden/context wiki : https://wiki.contextgarden.net ___________________________________________________________________________________ ^ permalink raw reply [flat|nested] 4+ messages in thread
* [NTG-context] Re: OpenType contextual alternates disabled by default 2025-09-09 7:59 ` [NTG-context] " Hans Hagen via ntg-context @ 2025-09-09 20:16 ` Wolfgang Schuster 2025-09-10 6:58 ` Hans Hagen via ntg-context 0 siblings, 1 reply; 4+ messages in thread From: Wolfgang Schuster @ 2025-09-09 20:16 UTC (permalink / raw) To: ntg-context Am 09.09.2025 um 09:59 schrieb Hans Hagen via ntg-context: > On 9/9/2025 9:34 AM, Max Chernoff via ntg-context wrote: >> Hi Hans, >> >> OpenType contextual alternates ("calt") seem to be disabled by default >> in ConTeXt. However, the OpenType spec recommends that this is enabled >> by default >> >> https://learn.microsoft.com/en-us/typography/opentype/spec/ >> features_ae#tag-calt >> >> and it's enabled by default in both HTML and HarfBuzz >> >> https://drafts.csswg.org/css-fonts/#default-features >> >> https://harfbuzz.github.io/shaping-opentype-features.html >> >> Changing this default in ConTeXt probably isn't possible due to >> backwards compatibility concerns, so this is more of an FYI than a >> request for any changes to be made. >> >> Background: this came up in a recent TeX.SE question >> >> https://tex.stackexchange.com/a/750767 >> >> where a new user was surprised by ConTeXt's default setting since it >> makes some fonts render differently than other programs. > > We started with opentype support (2005) when there wasn't much info > about it. The reference implementation was uniscribe so we had to guess > and compare with that. The xetex engine was using some libraries and > changed them later on. So we couldn't check that out either. > > Now, when it comes to features, those experiences, also with specific > fonts, made us decide for the defaults. Over time the specification > became better and more complete but as you say: we want to remain > compatibility. (I assume that ltx folk spend substantial time on > checking changes in hb every time there is an update in tex live, which > is quite often if i look at git syncing.) > > An omission in otf is that the font doesn't specify what features are to > be on by default. Combine that with font usage where users have no > control over features, and we see why soem are just turned on. Probably > the same for some (fixing) heuristics. It's now how tex works: there we > *ask* for something, not being *enforced* to. > > If I could motivate myself we could of course make such a list of > default features per font. > > Of course one can wonder why we have rlig/lig/clig as well as kern/dist > split into several features when they are supposed to be always on. But > I will not waste time on pondering that. A simple change is to a additional feature set with all the new recommended settings. Changes to the list can happen unlike the default feature set and users can apply it to their own font settings. \definefontfeature [standard] % harfbuzz? [always] [itlc=yes, rlig=yes, liga=yes, clig=yes, calt=yes] \starttext {\definedfont[name:playwritegbjregular*default]Whereas recognition of the inherent dignity} {\definedfont[name:playwritegbjregular*standard]Whereas recognition of the inherent dignity} \stoptext Wolfgang ___________________________________________________________________________________ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / https://mailman.ntg.nl/mailman3/lists/ntg-context.ntg.nl webpage : https://www.pragma-ade.nl / https://context.aanhet.net (mirror) archive : https://github.com/contextgarden/context wiki : https://wiki.contextgarden.net ___________________________________________________________________________________ ^ permalink raw reply [flat|nested] 4+ messages in thread
* [NTG-context] Re: OpenType contextual alternates disabled by default 2025-09-09 20:16 ` Wolfgang Schuster @ 2025-09-10 6:58 ` Hans Hagen via ntg-context 0 siblings, 0 replies; 4+ messages in thread From: Hans Hagen via ntg-context @ 2025-09-10 6:58 UTC (permalink / raw) To: ntg-context; +Cc: Hans Hagen On 9/9/2025 10:16 PM, Wolfgang Schuster wrote: > Am 09.09.2025 um 09:59 schrieb Hans Hagen via ntg-context: >> On 9/9/2025 9:34 AM, Max Chernoff via ntg-context wrote: >>> Hi Hans, >>> >>> OpenType contextual alternates ("calt") seem to be disabled by default >>> in ConTeXt. However, the OpenType spec recommends that this is enabled >>> by default >>> >>> https://learn.microsoft.com/en-us/typography/opentype/spec/ >>> features_ae#tag-calt >>> >>> and it's enabled by default in both HTML and HarfBuzz >>> >>> https://drafts.csswg.org/css-fonts/#default-features >>> >>> https://harfbuzz.github.io/shaping-opentype-features.html >>> >>> Changing this default in ConTeXt probably isn't possible due to >>> backwards compatibility concerns, so this is more of an FYI than a >>> request for any changes to be made. >>> >>> Background: this came up in a recent TeX.SE question >>> >>> https://tex.stackexchange.com/a/750767 >>> >>> where a new user was surprised by ConTeXt's default setting since it >>> makes some fonts render differently than other programs. >> >> We started with opentype support (2005) when there wasn't much info >> about it. The reference implementation was uniscribe so we had to >> guess and compare with that. The xetex engine was using some libraries >> and changed them later on. So we couldn't check that out either. >> >> Now, when it comes to features, those experiences, also with specific >> fonts, made us decide for the defaults. Over time the specification >> became better and more complete but as you say: we want to remain >> compatibility. (I assume that ltx folk spend substantial time on >> checking changes in hb every time there is an update in tex live, >> which is quite often if i look at git syncing.) >> >> An omission in otf is that the font doesn't specify what features are >> to be on by default. Combine that with font usage where users have no >> control over features, and we see why soem are just turned on. >> Probably the same for some (fixing) heuristics. It's now how tex >> works: there we *ask* for something, not being *enforced* to. >> >> If I could motivate myself we could of course make such a list of >> default features per font. >> >> Of course one can wonder why we have rlig/lig/clig as well as kern/ >> dist split into several features when they are supposed to be always >> on. But I will not waste time on pondering that. > > A simple change is to a additional feature set with all the new > recommended settings. Changes to the list can happen unlike the default > feature set and users can apply it to their own font settings. > > \definefontfeature > [standard] % harfbuzz? > [always] > [itlc=yes, > rlig=yes, > liga=yes, > clig=yes, > calt=yes] > > \starttext more like "recommended" as there is no standard and specific applications are no standard either .. font-pre has a comment: % ccmp=yes, % maybe too % locl=yes, % maybe too % calt=yes, % maybe too % clig=yes, % maybe too % rlig=yes, % maybe too % tlig=yes, % no longer default (texligatures=yes) % trep=yes, % no longer default (texquotes=yes) so shouln't we then also add ccmp and locl there? \definefontfeature [recommended] [always] [itlc=yes, % ccmp=yes, % locl=yes, rlig=yes, liga=yes, clig=yes, calt=yes] Because I guess those will be next. We (us users) can add more as more becomes 'recommended' . Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl ----------------------------------------------------------------- ___________________________________________________________________________________ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / https://mailman.ntg.nl/mailman3/lists/ntg-context.ntg.nl webpage : https://www.pragma-ade.nl / https://context.aanhet.net (mirror) archive : https://github.com/contextgarden/context wiki : https://wiki.contextgarden.net ___________________________________________________________________________________ ^ permalink raw reply [flat|nested] 4+ messages in thread
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