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Posted to dev@pdfbox.apache.org by "Maruan Sahyoun (Jira)" <ji...@apache.org> on 2023/10/16 18:16:00 UTC
[jira] [Commented] (PDFBOX-5700) Ligature substitution cannot be switched off
[ https://issues.apache.org/jira/browse/PDFBOX-5700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17775876#comment-17775876 ]
Maruan Sahyoun commented on PDFBOX-5700:
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I'd think that for most purposes the features should be on with possibilities for the developer to control some of the features. E.g. to allow to suppress ligatures we could be supporting the Zero Width Non-Joiner (ZWNJ) control character or disable by script, language, writing mode ...
> Ligature substitution cannot be switched off
> --------------------------------------------
>
> Key: PDFBOX-5700
> URL: https://issues.apache.org/jira/browse/PDFBOX-5700
> Project: PDFBox
> Issue Type: Bug
> Components: FontBox
> Affects Versions: 3.0.0 PDFBox
> Reporter: Tilman Hausherr
> Priority: Major
>
> It is not possible to switch off the ligature substitution if one doesn't ligatures or if the ligatures are faulty, as mentioned in the linked SO question.
> The {{disableGsubFeature}} call works only for vertical fonts, which uses a strategy that is completely different than ligatures or indian font substitution.
> How it works currently: PDAbstractContentStream uses GsubWorkerFactory to get a GsubWorker. That one doesn't have access to the information whether GsubFeatures are enabled or disabled. It doesn't even have access to a TrueTypeFont object.
> The simplest solution would be to enable or disable substitutions at the PDType0Font level. A better solution would be to switch individual Gsub features (FEATURES_IN_ORDER in the GSubworkers) on and off.
> What's also unclear is if it should be on by default or off by default. Indian substitutions should be on. European ligatures are nice, but not really important. Then there are some "fun" features like "Swash" (swsh).
> https://en.wikipedia.org/wiki/List_of_typographic_features
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