Variable fonts broken with World Ready Paragraph Composer
Using the World-ready composer essentially breaks the glyph width interpolation of Variable Fonts. The outcome is that text set in a Variable Font will receive the Variable Font's default style's horizontal glyph widths for any axis location, resulting in unusable overlap or gaps.
Attached you find a sample Indesign file with comparison and a screenshot thereof. This happens with any Variable Font I have tested so var, but to complete the same test case as included, download https://github.com/adobe-fonts/source-sans-pro/releases/download/3.006R/source-sans-pro-3.006R.zip and install VAR/SourceSansVariable-Roman.otf as well as OTF/*.otf files.
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Jany Belluz commented
This issue also happens in Arabic (where using the World-Ready composers is absolutely necessary).
See the attached picture of Markazi Text, which exhibits two problems:
* The advance widths do not variate when using the VF (red line showing how the line lengths match when they shouldn't)
* Mark positioning does not variate either, or is generally wrong (orange and green rectangles)
The advance width problem is particularly bad when using a thin weight that has a lower advance width: it makes the letters disconnect from each other.
The Markazi Text font can be downloaded from: https://github.com/BornaIz/markazitext/tree/master/fonts
As an aside: there are 2 other copies of this discussion, could you please merge them or delete the others? I commented on another one already that has 3 votes, but I'm copying my comment here as this discussion seems to have been noticed by Adobe. Thanks in advance!