emilk/egui · error

Invalid variation axis tag

Error message

Invalid variation axis tag

What it means

Error "Invalid variation axis tag" thrown in emilk/egui.

Solutions

1. Use a valid 4-character OpenType variation axis tag (e.g. "wght", "wdth") for the font variation.

Example fix

font_data.tweak.variations.push((ab_glyph::Tag::new(b"wght"), 700.0));

When it happens

Trigger: Thrown at crates/epaint/src/text/text_layout_types.rs:396 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of emilk/egui@b9a0723d88 (2026-08-19). Data as JSON: /api/errors/3391f853ed7b99aa. Report an issue: GitHub.

Appendix: source

Thrown at crates/epaint/src/text/text_layout_types.rs:396

impl IntoTag for font_types::Tag {
    #[inline(always)]
    fn into_tag(self) -> font_types::Tag {
        self
    }
}

impl IntoTag for u32 {
    #[inline(always)]
    fn into_tag(self) -> font_types::Tag {
        font_types::Tag::from_u32(self)
    }
}

impl IntoTag for [u8; 4] {
    #[inline(always)]
    fn into_tag(self) -> font_types::Tag {
        font_types::Tag::new_checked(&self).expect("Invalid variation axis tag")
    }
}

impl IntoTag for &[u8; 4] {
    #[inline(always)]
    fn into_tag(self) -> font_types::Tag {
        font_types::Tag::new_checked(self).expect("Invalid variation axis tag")
    }
}

impl IntoTag for &str {
    #[inline(always)]
    fn into_tag(self) -> font_types::Tag {
        font_types::Tag::from_str(self).expect("Invalid variation axis tag")
    }
}

/// List of font variation coordinates by axis tag. If more than one coordinate for a given axis is provided, the last

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