embedded-gui 0.1.3

no_std GUI and HUD primitives for embedded-graphics displays
Documentation 
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include!(concat!(env!("OUT_DIR"), "/generated_ascii_3x5.rs"));

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct PackedFont {
    pub first_char: u8,
    pub advance: u8,
    pub line_height: u8,
    pub glyphs: &'static [[u8; 5]],
}

pub static ASCII_3X5_FONT: PackedFont = PackedFont {
    first_char: 32,
    advance: 4,
    line_height: 6,
    glyphs: &ASCII_3X5_GLYPHS,
};

pub static ASCII_4X7_FONT: PackedFont = PackedFont {
    first_char: 32,
    advance: 5,
    line_height: 8,
    glyphs: &ASCII_4X7_GLYPHS,
};

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum FontId {
    Tiny3x5,
    Medium4x7,
    Scaled6x10,
    Custom(&'static PackedFont),
}

impl FontId {
    pub const fn advance(self) -> u32 {
        match self {
            Self::Tiny3x5 => 4,
            Self::Medium4x7 => 5,
            Self::Scaled6x10 => 7,
            Self::Custom(font) => font.advance as u32,
        }
    }

    pub const fn line_height(self) -> u32 {
        match self {
            Self::Tiny3x5 => 6,
            Self::Medium4x7 => 8,
            Self::Scaled6x10 => 11,
            Self::Custom(font) => font.line_height as u32,
        }
    }
}

pub const fn packed_font(font: FontId) -> &'static PackedFont {
    match font {
        FontId::Tiny3x5 => &ASCII_3X5_FONT,
        FontId::Medium4x7 => &ASCII_4X7_FONT,
        FontId::Scaled6x10 => &ASCII_3X5_FONT,
        FontId::Custom(font) => font,
    }
}

pub fn glyph_rows(font: FontId, ch: char) -> [u8; 5] {
    let packed = packed_font(font);
    let code = ch as u32;
    if code >= packed.first_char as u32 {
        let idx = (code as usize).saturating_sub(packed.first_char as usize);
        if idx < packed.glyphs.len() {
            return packed.glyphs[idx];
        }
    }
    let fallback = b'?'.saturating_sub(packed.first_char) as usize;
    packed.glyphs.get(fallback).copied().unwrap_or([0; 5])
}

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

    static MY_CUSTOM_GLYPHS: [[u8; 5]; 2] = [
        [0b111, 0b101, 0b111, 0b101, 0b101], // Space / 'A'
        [0b111, 0b111, 0b111, 0b111, 0b111],
    ];

    static MY_CUSTOM_FONT: PackedFont = PackedFont {
        first_char: 32,
        advance: 8,
        line_height: 12,
        glyphs: &MY_CUSTOM_GLYPHS,
    };

    #[test]
    fn test_custom_font_id() {
        let font_id = FontId::Custom(&MY_CUSTOM_FONT);
        assert_eq!(font_id.advance(), 8);
        assert_eq!(font_id.line_height(), 12);
        assert_eq!(packed_font(font_id).first_char, 32);
        assert_eq!(
            glyph_rows(font_id, ' '),
            [0b111, 0b101, 0b111, 0b101, 0b101]
        );
    }
}