What causes "SelectorStyle try_from:: () for value {} failed" in flxzt/rnote?

Check that the u32 corresponds to a valid SelectorStyle discriminant (see selectorconfig.rs).

SelectorStyle try_from

Error message

SelectorStyle try_from::<u32>() for value {} failed

What it means

SelectorStyle::try_from(u32) failed because no SelectorStyle variant (e.g. polygon) matches the given u32 via num_traits::FromPrimitive. The library throws this when a numeric selector-style value, usually restored from persisted settings, is not a valid variant discriminant.

Solutions

Check that the u32 corresponds to a valid SelectorStyle discriminant (see selectorconfig.rs).
Fall back to SelectorStyle::default() when conversion fails on loaded settings.
Migrate or re-save settings produced by older app versions.

Example fix

// before
let style = SelectorStyle::try_from(stored_u32)?;
// after
let style = SelectorStyle::try_from(stored_u32)
    .unwrap_or(SelectorStyle::default());

Defensive patterns

Strategy: fallback

Validate before calling

fn is_valid_selector_style(v: u32) -> bool {
    SelectorStyle::try_from(v).is_ok()
}

Type guard

fn as_selector_style(v: u32) -> Option<SelectorStyle> {
    num_traits::FromPrimitive::from_u32(v)
}

Try / catch

let style = SelectorStyle::try_from(raw)
    .map_err(|e| log::warn!("{e}; using default"))
    .unwrap_or(SelectorStyle::default());

Prevention

Clamp or validate UI dropdown indices against the enum variant count before conversion.
Migrate persisted selector settings when the enum layout changes.
Prefer name-based enum serialization over raw discriminants.

When it happens

Trigger: Calling `SelectorStyle::try_from(value)` with a u32 outside valid discriminants, e.g. a value from an old settings file after variants changed, or an out-of-range UI selector index.

Common situations: Restoring selector pen configuration across rnote versions; hand-edited config; a GUI dropdown index that no longer maps to a variant.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of flxzt/rnote@bbc5354502 (2026-09-08). Data as JSON: /api/errors/0e82244984da4888. Report an issue: GitHub.

Appendix: source

Thrown at crates/rnote-engine/src/pens/pensconfig/selectorconfig.rs:40

    Rectangle,
    #[serde(rename = "single", alias = "apiece")]
    Single,
    #[serde(rename = "intersectingpath")]
    IntersectingPath,
}

impl Default for SelectorStyle {
    fn default() -> Self {
        Self::Rectangle
    }
}

impl TryFrom<u32> for SelectorStyle {
    type Error = anyhow::Error;

    fn try_from(value: u32) -> Result<Self, Self::Error> {
        num_traits::FromPrimitive::from_u32(value).ok_or_else(|| {
            anyhow::anyhow!("SelectorStyle try_from::<u32>() for value {} failed", value)
        })
    }
}

#[derive(Clone, Debug, Serialize, Deserialize)]
#[serde(default, rename = "selector_config")]
pub struct SelectorConfig {
    #[serde(rename = "style")]
    pub style: SelectorStyle,
    #[serde(rename = "resize_lock_aspectratio")]
    pub resize_lock_aspectratio: bool,
}

impl Default for SelectorConfig {
    fn default() -> Self {
        Self {
            style: SelectorStyle::default(),
            resize_lock_aspectratio: false,

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