Issue with smart components and decomposition

I am trying an approach of separating mark shaping from positioning by nesting components but am running into an issue with how the final component decomposes after export. I am using the following approach:

  1. I start with a non-exporting glyph to only use for shaping (drawing the outlines of the mark)
  2. Next, I add a smart component with two layers, inserting the shaping glyph as a component in each layer at different vertical positions and adding _top anchors. (Ideally, the smart component parameters are set up to make sense with the vertical position values)
  3. The smart component is then inserted into the exporting glyph, where the position parameter value can be set.
  4. This exporting glyph is then inserted as a component into .comb (non-spacing mark). In the ccmp feature, .comb is substituted to combine with a glyph with a top anchor.

With this set-up, the shape of the mark can be determined in step 1 then the position can be set using the parameter slider in step 3, which will automatically update the combining glyph of step 4.

The issue I am running into is that after export the combining mark decomposes to the original shape position in step 1, ignoring the anchors and position set using the smart component.

Any thoughts on what could be causing this? or if I can try to set up this idea in another way?

Version 2.6.5 (1330)

Here a simplified demo:


Can you upload the demo file?

smart_component_test_1.glyphs (11.6 KB)

@mekkablue any luck reproducing the issue?