pixbar 0.2.0

Sub-cell-precision two-value progress bar for narrow terminal widths (Unicode 1/8 block, no font patching required).
Documentation 
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//! Capability-specific glyph tables.
//!
//! [`glyph_for`] is the only entry point. It dispatches on [`Capability`]
//! and returns the single `char` that should be printed for a given
//! [`CellKind`] + `sub_fill` pair. Empty cells always return space; full
//! cells always return `█` (`U+2588`).

use crate::{render::CellKind, Capability};

/// Resolve a [`CellKind`] + `sub_fill` to the `char` that should be drawn
/// under the given [`Capability`].
pub fn glyph_for(kind: CellKind, sub_fill: u8, cap: Capability) -> char {
    match cap {
        Capability::Ascii       => ascii(kind),
        Capability::EighthBlock => eighth(kind, sub_fill),
    }
}

fn ascii(kind: CellKind) -> char {
    match kind {
        CellKind::Empty => ' ',
        CellKind::PrimaryFull
        | CellKind::SecondaryFull
        | CellKind::OverflowFull
        | CellKind::PrimaryBoundary
        | CellKind::SecondaryBoundary
        | CellKind::OverflowInnerBoundary
        | CellKind::OverflowOuterBoundary
        | CellKind::DegradedOverlap => '█',
    }
}

fn eighth(kind: CellKind, sub_fill: u8) -> char {
    // Unicode left 1/8 block ladder: space ▏▎▍▌▋▊▉█ — indexed 0..=8.
    const TABLE: [char; 9] = [' ', '▏', '▎', '▍', '▌', '▋', '▊', '▉', '█'];
    match kind {
        CellKind::Empty => ' ',
        CellKind::PrimaryFull
        | CellKind::SecondaryFull
        | CellKind::OverflowFull => '█',
        CellKind::PrimaryBoundary
        | CellKind::SecondaryBoundary
        | CellKind::OverflowInnerBoundary
        | CellKind::OverflowOuterBoundary
        | CellKind::DegradedOverlap => TABLE[sub_fill.min(8) as usize],
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test] fn ascii_full() {
        assert_eq!(glyph_for(CellKind::PrimaryFull, 0, Capability::Ascii), '█');
    }
    #[test] fn ascii_empty() {
        assert_eq!(glyph_for(CellKind::Empty, 0, Capability::Ascii), ' ');
    }
    #[test] fn eighth_half() {
        assert_eq!(glyph_for(CellKind::PrimaryBoundary, 4, Capability::EighthBlock), '▌');
    }
    #[test] fn eighth_zero_sub_is_space() {
        assert_eq!(glyph_for(CellKind::PrimaryBoundary, 0, Capability::EighthBlock), ' ');
    }
    #[test] fn eighth_full_sub_is_full_block() {
        assert_eq!(glyph_for(CellKind::PrimaryBoundary, 8, Capability::EighthBlock), '█');
    }
}