spandex 0.0.2

A modern LaTeX alternative
Documentation 
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//! Various blocks holding information and specifications about the structure
//! of a paragraph.

use printpdf::Pt;

use crate::typography::Glyph;

/// Top abstraction of an item, which is a specification for a box, a glue
/// or a penalty.
#[derive(Debug)]
pub struct Item<'a> {
    /// The width of the item in scaled units.
    pub width: Pt,

    /// The type of the item.
    pub content: Content<'a>,
}

/// Possible available types for an item.
#[derive(Debug)]
pub enum Content<'a> {
    /// A bounding box refers to something that is meant to be typeset.
    ///
    /// Though it holds the glyph it's representing, this item is
    /// essentially a black box as the only revelant information
    /// about it for splitting a paragraph into lines is its width.
    BoundingBox(Glyph<'a>),
    /// Glue is a blank space which can see its width altered in specified ways.
    ///
    /// It can either stretch or shrink up to a certain limit, and is used as
    /// mortar to leverage to reach a target column width.
    Glue {
        /// How inclined the glue is to stretch from its natural width, in scaled points.
        stretchability: Pt,

        /// How inclined the glue is to shrink from its natural width, in scaled points.
        shrinkability: Pt,
    },
    /// Penalty is a potential place to end a line and step to another. It's helpful
    /// to cut a line in the middle of a word (hyphenation) or to enforce a break
    /// at the end of paragraphs.
    Penalty {
        /// The "cost" of the penalty.
        value: f64,

        /// Whether or not the penalty is considered as flagged.
        flagged: bool,
    },
}

impl<'a> Item<'a> {
    /// Creates a box for a particular glyph and font.
    pub fn from_glyph(glyph: Glyph<'a>) -> Item<'a> {
        Item {
            width: glyph.font.char_width(glyph.glyph, glyph.scale),
            content: Content::BoundingBox(glyph),
        }
    }

    /// Creates some glue.
    pub fn glue(ideal_spacing: Pt, stretchability: Pt, shrinkability: Pt) -> Item<'a> {
        Item {
            width: ideal_spacing,
            content: Content::Glue {
                stretchability,
                shrinkability,
            },
        }
    }

    /// Creates a penalty.
    pub fn penalty(width: Pt, value: f64, flagged: bool) -> Item<'a> {
        Item {
            width,
            content: Content::Penalty { value, flagged },
        }
    }
}

/// Holds the information of an item that's ready to be rendered.
#[derive(Debug)]
pub struct PositionedItem<'a> {
    /// The index of the item within the list of items that make up
    /// the paragraph in which is stands.
    pub index: usize,

    /// The index of the line on which this item is to be rendered.
    pub line: usize,

    /// The horizontal offset of the item.
    pub horizontal_offset: Pt,

    /// The (potentially adjusted) width this item should be rendered with.
    pub width: Pt,

    /// The glyph that should be layed out within this item.
    pub glyph: Glyph<'a>,
}