charton 0.5.0

A high-performance, layered charting system for Rust, featuring a flexible data core and multi-backend rendering.
Documentation 
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/// Represents a secondary Y-axis encoding specification (Y2).
///
/// `Y2` is typically used for visual marks that require two vertical coordinates,
/// such as the baseline of an Area chart, the second endpoint of a Rule,
/// or the "start" value of a Bar.
///
/// ### Architecture Note:
/// Unlike `X` or `Y`, `Y2` does not usually define its own scale logic (domain, type, etc.).
/// Instead, it maps a different data field onto the **same** scale as `Y`.
/// For instance, in an Area chart, `Y` might map to "high_price" and `Y2` to "low_price",
/// but both must use the same vertical coordinate system to be visually coherent.
#[derive(Debug, Clone)]
pub struct Y2 {
    // --- User Configuration (Intent/Inputs) ---
    /// The name of the data column to be mapped to the secondary vertical position.
    pub(crate) field: String,
    // --- System Resolution (Result/Outputs) ---

    // Stores the resolved scale instance. Using RwLock to support
    // back-filling updates across multiple render calls.
    //pub(crate) resolved_scale: RwLock<Option<Arc<dyn ScaleTrait>>>,
}

impl Y2 {
    /// Creates a new Y2 encoding for the specified data field.
    pub fn new(field: &str) -> Self {
        Self {
            field: field.to_string(),
            //resolved_scale: RwLock::new(None),
        }
    }
}

/// Convenience builder function to create a new Y2 encoding.
///
pub fn y2(field: &str) -> Y2 {
    Y2::new(field)
}