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[ttml2] Add support for font variation settings

From: Nigel Megitt via GitHub <sysbot+gh@w3.org>
Date: Fri, 07 Jul 2017 10:27:32 +0000
To: public-tt@w3.org
Message-ID: <issues.opened-241223556-1499423251-sysbot+gh@w3.org>
nigelmegitt has just created a new issue for https://github.com/w3c/ttml2:

== Add support for font variation settings ==
Raising this as a placeholder for a possible future requirement, maybe on TTML2 or a future version. I have had recent internal feedback from BBC that we may need this feature.

Adding support for font variation settings, i.e. directing the presentation processor to set particular OpenType/TrueType font variation settings can be helpful. The specific example that has arisen is whether to use proportional or tabular variations for numbers. This is the `tnum` setting.

The choice of tabular/proportional affects readability in different ways in different circumstances:

-  If using TTML to present something with numbers that change over time, in the same overall position, like a clock or a countdown timer, using tabular numbers prevents the inline position of individual digits from wobbling around as the number changes; 
-  however if presenting a static number as part of text to be read, using proportional numbers is considered easier on the eye by some viewers (research evidence for this claim needs investigating: a quick search suggests the evidence is thin or contrary to this position by the way, i.e. it might make no difference to readability at all). 

The default setting varies by font, but many fonts offer both options.

Please view or discuss this issue at https://github.com/w3c/ttml2/issues/399 using your GitHub account
Received on Friday, 7 July 2017 10:27:38 UTC

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