Kerning with Text

[Guest]

So, i know the Indesign team helped with the Text Layout Framework, and I am actually using IDML alongside the framework to produce stuff (http://troyblank.com/workSamples/IDMLParser/)

My question is about Kerning, so Indesign has Optical and Metric kerning if i understand kerning correctly, but the framework only kerns or not kerns, but from experimentation it appears the type of kerning the framework can only do is what Indesign calls optical, can anyone confirm this?

Also if this is the case is there any plans to utlize any other kerning tables via the text layout framework?

[dslatton]

Actually, kerning in TLF uses kern tables provided by the font. The "auto" kern setting in TLF means use the font kern table for Roman fonts. Setting kerning to "On" applies kerning to Roman and double-byte text (Japanese, Chinese), and "off" turns off font kerning entirely. Manual kerning can be obtained by using the tracking values to individual letter-pairs.

Optical kerning, which calculates visually appealing kerning based on the glyph shapes instead of using internal font metric tables, is not available in TLF.

[robin_briggs]

InDesign has several features in this area. Metric kerning controls whether the kern table in the font is used when laying out text. Manual kerning is an adjustment the user can specify in the document that is applied instead of using the value from the font. Optical kerning will run an algorithm on the characters to dynamically deduce a kern value. And there is an additional feature called "tracking", which is very similar to manual kerning, but the adjustment value is applied in addition to whatever kern adjustments are defined.

TLF just has metric kerning and tracking. You should be able to get the same effect as manual tracking by turning the kerning off, and applying a tracking value. Tracking in TLF is a little different than InDesign, because it allows you to specify whether the tracking should apply to the left or right side of the character, which is useful in bidi situations to prevent over kerning.TLF does not implement optical kerning.

- robin