Historically, there have been two methods of supporting vertical writing in CID-keyed OpenType/CFF fonts, in terms of specifying the ‘vert‘ (Vertical Alternates) GSUB feature. One method involved using a vertical CMap resource, which was supplied to the AFDKO makeotf tool as an argument to its no-longer-supported “-cv” command-line option, that was used to synthesize the ‘vert’ GSUB feature. The other method, which is the preferred one, involves defining a ‘vert’ GSUB feature in the “features” file that is supplied to the AFDKO makeotf tool. In this brief article, I will explain why the first method is no longer supported, but more importantly, why the second method is preferred.
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