flattenComponents breaks composed positioning on nested + transformed combining accent

[arrowtype]

I have attempted to use the flattenComponents filter in a UFO based on the advice here: fonttools/fontbakery#2961 (comment)

<key>com.github.googlei18n.ufo2ft.filters</key>
    <array>
      <dict>
        <key>name</key>
        <string>flattenComponents</string>
        <key>pre</key>
        <integer>1</integer>
      </dict>
    </array>

It mostly works well! However, a notable exception is that my caroncomb accents, which are actually composed of the circumflexcomb rotated 180°. These caroncombs are decomposed, which is good, but the alignment in glyphs using them gets messed up once I use FontMake to export to a TTF:

By comparison, here is a TTF built from a UFO that didn’t have a flattenComponents filter:

These are not open-source UFOs, so I can try to report back later with an OS reproduction case, if that is needed to diagnose & fix this problem.

[anthrotype]

you may want to try using the decomposeTransformedComponents filter before the flattenComponents

[arrowtype]

Thanks for the quick response! It works like a charm. 👍

Cheers! Feel free to close this issue if you feel that this is handled as expected.

[anthrotype]

I would think so, yes. Cheers 🍻