DioxusLabs/dioxus · error

Invalid delta mode, {:?}

Error message

Invalid delta mode, {:?}

What it means

WheelDelta::from_web_attributes received a deltaMode value outside the DOM wheel event spec (0=pixels, 1=lines, 2=pages). Any other u32 falls through the match to the error arm carrying the unrecognized mode.

Source

Thrown at packages/html/src/geometry.rs:74

#[derive(Copy, Clone, Debug, PartialEq)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
pub enum WheelDelta {
    /// Movement in Pixels
    Pixels(PixelsVector3D),
    /// Movement in Lines
    Lines(LinesVector),
    /// Movement in Pages
    Pages(PagesVector),
}

impl WheelDelta {
    /// Construct from the attributes of the web wheel event
    pub fn from_web_attributes(delta_mode: u32, delta_x: f64, delta_y: f64, delta_z: f64) -> Self {
        match delta_mode {
            0 => WheelDelta::Pixels(PixelsVector3D::new(delta_x, delta_y, delta_z)),
            1 => WheelDelta::Lines(LinesVector::new(delta_x, delta_y, delta_z)),
            2 => WheelDelta::Pages(PagesVector::new(delta_x, delta_y, delta_z)),
            _ => panic!("Invalid delta mode, {:?}", delta_mode),
        }
    }

    /// Convenience function for constructing a WheelDelta with pixel units
    pub fn pixels(x: f64, y: f64, z: f64) -> Self {
        WheelDelta::Pixels(PixelsVector3D::new(x, y, z))
    }

    /// Convenience function for constructing a WheelDelta with line units
    pub fn lines(x: f64, y: f64, z: f64) -> Self {
        WheelDelta::Lines(LinesVector::new(x, y, z))
    }

    /// Convenience function for constructing a WheelDelta with page units
    pub fn pages(x: f64, y: f64, z: f64) -> Self {
        WheelDelta::Pages(PagesVector::new(x, y, z))
    }

View on GitHub (pinned to 24f6a829df)

Solutions

1. An unknown wheel delta mode was received. Handle only pixel/line/page modes; update dioxus if the platform emits a new mode.

When it happens

Trigger: Thrown at packages/html/src/geometry.rs:74 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of DioxusLabs/dioxus@24f6a829df (2026-08-23). Data as JSON: /api/errors/070910c137bd01b7. Report an issue: GitHub.