[VARC] Special-case hidden axes when applying RESET_UNSPECIFIED_AXES to pen.addVarComponent() #3549
Conversation
I'm a bit uncomfortable with that. Can we change the protocol and send two locations down? |
Hm, then we burden the addVarComponent signature with this problem. Not sure which is better. The way we currently compile with RESET_UNSPECIFIED_AXES already depends on those axes always being at the default: as soon as you set one to a non-default value, the font breaks, as can be seen in (my private build of) FontGoggles: Screen.Recording.2024-05-30.at.20.50.34.movSo those axes are already special, and to me special-casing them here doesn't make things worse. |
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Potentially we could amend the spec to say that RESET_UNSPECIFIED_AXES should reset to the current location for non-hidden axes, and to default for hidden axes? |
What if we add a lower-level Let me also think more. In my compiler I drop encoding axes if they have the same value as the parent glyph. Let me think more about your requirements and get back to you. |
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I'm having a hard time to come up with a use case for pen.addVarComponent() that is other than mine... There is of course the option that I don't use the pen protocol for this at all, and just read VARC directly. Maybe that makes more sense. There's also your earlier idea if having two flags:
The first is handy when we pass down (user) axes to deeply nested components. The second is what we really need for private axes. |
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(Hm, additionally, pen.addVarComponent() doesn't support extracting conditions (which Fontra doesn't yet support), but that also suggests that the pen protocol is perhaps not the right tool to extract variable components.) |
Alternative to #3541.
As explained in #3541 (review), the rawLocation mechanism is needed to meaningfully extract variable components via addVarComponent().
But this gives a bit of a conundrum with the new meaning of RESET_UNSPECIFIED_AXES.
Old meaning: when RESET_UNSPECIFIED_AXES is set, reset unspecified axes to default
New meaning: when RESET_UNSPECIFIED_AXES is set, reset unspecified axes the current font location
Long story short, to implement RESET_UNSPECIFIED_AXES in a useful way for addVarComponent(), we need to special case hidden axes.