bevy_text 0.20.0

use crate::{Font, InlineBox, TextBrush, TextError, TextLayoutInfo, TextSection};
use alloc::borrow::Cow;
use bevy_asset::{Assets, Handle};
use bevy_color::Color;
use bevy_derive::{Deref, DerefMut};
use bevy_ecs::{prelude::*, reflect::ReflectComponent};
use bevy_math::Vec2;
use bevy_reflect::prelude::*;
use bevy_utils::{default, once};
use core::fmt::{Debug, Formatter};
use core::str::from_utf8;
use parley::setting::Tag;
use parley::{FontFamily, FontFeature, FontVariation, Layout};
use serde::{Deserialize, Serialize};
use smallvec::SmallVec;
use smol_str::SmolStr;
use tracing::warn;

/// A sub-entity of a [`ComputedTextBlock`].
///
/// Returned by [`ComputedTextBlock::entities`].
#[derive(Debug, Copy, Clone, Reflect)]
#[reflect(Debug, Clone)]
pub struct TextEntity {
    /// The entity.
    pub entity: Entity,
    /// Records the hierarchy depth of the entity within a `TextLayout`.
    pub depth: usize,
    /// Antialiasing method to use when rendering the text.
    pub font_smoothing: FontSmoothing,
}

/// Computed information for a text block.
///
/// See [`TextLayout`].
///
/// Automatically updated by 2d and UI text systems.
#[derive(Component, Clone, Reflect)]
#[reflect(Component, Debug, Default, Clone)]
pub struct ComputedTextBlock {
    /// Text layout, used to generate [`TextLayoutInfo`].
    #[reflect(ignore, clone)]
    pub(crate) layout: Layout<TextBrush>,
    /// Entities for all text spans in the block, including the root-level text.
    ///
    /// The [`TextEntity::depth`] field can be used to reconstruct the hierarchy.
    pub(crate) entities: SmallVec<[TextEntity; 1]>,
    /// Flag set when any change has been made to this block that should cause it to be rerendered.
    ///
    /// Includes:
    /// - [`TextLayout`] changes.
    /// - [`TextFont`] or `Text2d`/`Text`/`TextSpan` changes anywhere in the block's entity hierarchy.
    // TODO: This encompasses both structural changes like font size or justification and non-structural
    // changes like text color and font smoothing. This field currently causes UI to 'remeasure' text, even if
    // the actual changes are non-structural and can be handled by only rerendering and not remeasuring. A full
    // solution would probably require splitting TextLayout and TextFont into structural/non-structural
    // components for more granular change detection. A cost/benefit analysis is needed.
    pub(crate) needs_rerender: bool,
    // Flag set by `TextPipeline::update_buffer` if any text section in the block has a viewport font size value.
    //
    // Used by dependents to determine if they should update a text block on changes to
    // the viewport size.
    pub(crate) uses_viewport_sizes: bool,
    // Flag set by `TextPipeline::update_buffer` if any text section in the block has a rem font size value.
    //
    // Used by dependents to determine if they should update a text block on changes to
    // the rem size.
    pub(crate) uses_rem_sizes: bool,
}

impl Debug for ComputedTextBlock {
    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
        f.debug_struct("ComputedTextBlock")
            .field("layout", &"Layout(..)")
            .field("entities", &self.entities)
            .field("needs_rerender", &self.needs_rerender)
            .field("uses_viewport_sizes", &self.uses_viewport_sizes)
            .field("uses_rem_sizes", &self.uses_rem_sizes)
            .finish()
    }
}

impl ComputedTextBlock {
    /// Accesses entities in this block.
    ///
    /// Can be used to look up [`TextFont`] components for glyphs in [`TextLayoutInfo`] using the `section_index`
    /// stored there.
    pub fn entities(&self) -> &[TextEntity] {
        &self.entities
    }

    /// Indicates if the text needs to be refreshed in [`TextLayoutInfo`].
    ///
    /// Updated automatically by [`detect_text_needs_rerender`] and cleared
    /// by [`TextPipeline`](crate::TextPipeline) methods.
    pub fn needs_rerender(
        &self,
        is_viewport_size_changed: bool,
        is_rem_size_changed: bool,
    ) -> bool {
        self.needs_rerender
            || (is_viewport_size_changed && self.uses_viewport_sizes)
            || (is_rem_size_changed && self.uses_rem_sizes)
    }

    /// Accesses the shaped layout buffer.
    pub fn buffer(&self) -> &Layout<TextBrush> {
        &self.layout
    }
}

impl Default for ComputedTextBlock {
    fn default() -> Self {
        Self {
            layout: Layout::new(),
            entities: SmallVec::default(),
            needs_rerender: true,
            uses_rem_sizes: false,
            uses_viewport_sizes: false,
        }
    }
}

/// Component with text format settings for a block of text.
///
/// A block of text is composed of text spans, which each have a separate string value and [`TextFont`]. Text
/// spans associated with a text block are collected into [`ComputedTextBlock`] for layout, and then inserted
/// to [`TextLayoutInfo`] for rendering.
///
/// See `Text2d` in `bevy_sprite` for the core component of 2d text, and `Text` in `bevy_ui` for UI text.
#[derive(Component, Debug, Copy, Clone, Default, Reflect)]
#[reflect(Component, Default, Debug, Clone)]
#[require(ComputedTextBlock, TextLayoutInfo)]
pub struct TextLayout {
    /// The text's internal alignment.
    /// Should not affect its position within a container.
    pub justify: Justify,
    /// How the text should linebreak when running out of the bounds determined by `max_size`.
    pub linebreak: LineBreak,
}

impl TextLayout {
    /// Makes a new [`TextLayout`].
    pub const fn new(justify: Justify, linebreak: LineBreak) -> Self {
        Self { justify, linebreak }
    }

    /// Makes a new [`TextLayout`] with the specified [`Justify`].
    pub fn justify(justify: Justify) -> Self {
        Self::default().with_justify(justify)
    }

    /// Makes a new [`TextLayout`] with the specified [`LineBreak`].
    pub fn linebreak(linebreak: LineBreak) -> Self {
        Self::default().with_linebreak(linebreak)
    }

    /// Makes a new [`TextLayout`] with soft wrapping disabled.
    /// Hard wrapping, where text contains an explicit linebreak such as the escape sequence `\n`, will still occur.
    pub fn no_wrap() -> Self {
        Self::default().with_no_wrap()
    }

    /// Returns this [`TextLayout`] with the specified [`Justify`].
    pub const fn with_justify(mut self, justify: Justify) -> Self {
        self.justify = justify;
        self
    }

    /// Returns this [`TextLayout`] with the specified [`LineBreak`].
    pub const fn with_linebreak(mut self, linebreak: LineBreak) -> Self {
        self.linebreak = linebreak;
        self
    }

    /// Returns this [`TextLayout`] with soft wrapping disabled.
    /// Hard wrapping, where text contains an explicit linebreak such as the escape sequence `\n`, will still occur.
    pub const fn with_no_wrap(mut self) -> Self {
        self.linebreak = LineBreak::NoWrap;
        self
    }
}

/// A span of text in a tree of spans.
///
/// A `TextSpan` is only valid when it exists as a child of a parent that has either `Text` or
/// `Text2d`. The parent's `Text` / `Text2d` component contains the base text content. Any children
/// with `TextSpan` extend this text by appending their content to the parent's text in sequence to
/// form a [`ComputedTextBlock`]. The parent's [`TextLayout`] determines the layout of the block
/// but each node has its own [`TextFont`] and [`TextColor`].
#[derive(Component, Debug, Default, Clone, Deref, DerefMut, Reflect)]
#[reflect(Component, Default, Debug, Clone)]
#[require(TextFont, TextColor, LineHeight, LetterSpacing)]
pub struct TextSpan(pub String);

impl TextSpan {
    /// Makes a new text span component.
    pub fn new(text: impl Into<String>) -> Self {
        Self(text.into())
    }
}

impl TextSection for TextSpan {
    fn get_text(&self) -> &str {
        self.as_str()
    }
    fn get_text_mut(&mut self) -> &mut String {
        &mut *self
    }
}

impl From<&str> for TextSpan {
    fn from(value: &str) -> Self {
        Self(String::from(value))
    }
}

impl From<String> for TextSpan {
    fn from(value: String) -> Self {
        Self(value)
    }
}

/// Describes the horizontal alignment of multiple lines of text relative to each other.
///
/// This only affects the internal positioning of the lines of text within a text entity and
/// does not affect the text entity's position.
///
/// _Has no affect on a single line text entity_, unless used together with a
/// [`TextBounds`](super::bounds::TextBounds) component with an explicit `width` value.
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash, Reflect, Serialize, Deserialize)]
#[reflect(Serialize, Deserialize, Clone, PartialEq, Hash)]
#[doc(alias = "JustifyText")]
pub enum Justify {
    /// Leftmost character is immediately to the right of the render position.
    /// Bounds start from the render position and advance rightwards.
    #[default]
    Left,
    /// Leftmost & rightmost characters are equidistant to the render position.
    /// Bounds start from the render position and advance equally left & right.
    Center,
    /// Rightmost character is immediately to the left of the render position.
    /// Bounds start from the render position and advance leftwards.
    Right,
    /// Words are spaced so that leftmost & rightmost characters
    /// align with their margins.
    /// Bounds start from the render position and advance equally left & right.
    Justified,
    /// `TextAlignment::Left` for LTR text and `TextAlignment::Right` for RTL text.
    Start,
    /// `TextAlignment::Left` for RTL text and `TextAlignment::Right` for LTR text.
    End,
}

impl From<Justify> for parley::Alignment {
    fn from(justify: Justify) -> Self {
        match justify {
            Justify::Start => parley::Alignment::Start,
            Justify::End => parley::Alignment::End,
            Justify::Left => parley::Alignment::Left,
            Justify::Center => parley::Alignment::Center,
            Justify::Right => parley::Alignment::Right,
            Justify::Justified => parley::Alignment::Justify,
        }
    }
}

/// Determines how the font face for a text sections is selected.
///
/// A [`FontSource`] can be a handle to a font asset, a font family name,
/// a CSS font-family list, an ordered family list, or a generic font category
/// that is resolved using Parley's font database.
///
/// Font family fallback (selection of a font when the requested font is not found)
/// is automatically handled by [`parley::fontique`].
/// Be sure to enable the `parley/system` feature for automatic discovery of system fonts.
///
/// Generally speaking, these fallbacks are OS-specific,
/// and do not require manual configuration.
///
/// You can check which font family is used for a given [`FontSource`]
/// by calling [`FontCx::get_family`](crate::FontCx::get_family).
#[derive(Clone, Debug, Reflect, PartialEq, FromTemplate)]
pub enum FontSource {
    /// Use a specific font face referenced by a [`Font`] asset handle.
    ///
    /// If the default font handle is used, then
    /// * if `default_font` feature is enabled (enabled by default in `bevy` crate),
    ///   `FiraMono-subset.ttf` compiled into the library is used.
    /// * otherwise no text will be rendered, unless a custom font is loaded into the default font
    ///   handle.
    #[default]
    Handle(Handle<Font>),
    /// Resolve the font by family name using the font database.
    Family(SmolStr),
    /// Font family list in CSS format.
    ///
    /// For example: `"Arial, Noto Sans, sans-serif"`.
    Families(SmolStr),
    /// Ordered list of font sources.
    List(#[template(built_in)] Vec<FontSource>),
    /// Resolve the font using a generic font family.
    Generic(GenericFontFamily),
}

impl FontSource {
    /// Resolve the font by family name using the font database.
    pub fn family(family: impl Into<SmolStr>) -> Self {
        Self::Family(family.into())
    }

    /// Font family list in CSS format.
    ///
    /// For example: `"Arial, 'Noto Sans', sans-serif"`.
    pub fn families(source: impl Into<SmolStr>) -> Self {
        Self::Families(source.into())
    }

    /// Creates an ordered list of font sources.
    pub fn list<I, F>(list: I) -> Self
    where
        I: IntoIterator<Item = F>,
        F: Into<FontSource>,
    {
        Self::List(list.into_iter().map(Into::into).collect())
    }

    /// Returns a depth-first flattened list of sources, recursively replacing `FontSource::List` entries with their contents.
    pub fn flatten(&self) -> SmallVec<[&FontSource; 4]> {
        let mut sources = SmallVec::new();
        self.flatten_into(&mut sources);
        sources
    }

    fn flatten_into<'a>(&'a self, sources: &mut SmallVec<[&'a FontSource; 4]>) {
        match self {
            FontSource::List(font_sources) => {
                for source in font_sources {
                    source.flatten_into(sources);
                }
            }
            source => sources.push(source),
        }
    }

    /// Fonts with serifs — small decorative strokes at the ends of letterforms.
    ///
    /// Serif fonts are typically used for long passages of text and represent
    /// a more traditional or formal typographic style.
    pub const fn serif() -> Self {
        Self::Generic(GenericFontFamily::Serif)
    }
    /// Fonts without serifs.
    ///
    /// Sans-serif fonts generally have low stroke contrast and plain stroke
    /// endings, making them common for UI text and on-screen reading.
    pub const fn sans_serif() -> Self {
        Self::Generic(GenericFontFamily::SansSerif)
    }

    /// Fonts that use a cursive or handwritten style.
    ///
    /// Glyphs often resemble connected or flowing pen or brush strokes rather
    /// than printed letterforms.
    pub const fn cursive() -> Self {
        Self::Generic(GenericFontFamily::Cursive)
    }

    /// Decorative or expressive fonts.
    ///
    /// Fantasy fonts are primarily intended for display purposes and may
    /// prioritize visual style over readability.
    pub const fn fantasy() -> Self {
        Self::Generic(GenericFontFamily::Fantasy)
    }

    /// Fonts in which all glyphs have the same fixed advance width.
    ///
    /// Monospace fonts are commonly used for code, tabular data, and text
    /// where vertical alignment is important.
    pub const fn monospace() -> Self {
        Self::Generic(GenericFontFamily::Monospace)
    }

    /// The default user interface system font.
    pub const fn system_ui() -> Self {
        Self::Generic(GenericFontFamily::SystemUi)
    }

    /// Alternative serif font for user interfaces.
    pub const fn ui_serif() -> Self {
        Self::Generic(GenericFontFamily::UiSerif)
    }

    /// Alternative sans-serif font for user interfaces.
    pub const fn ui_sans_serif() -> Self {
        Self::Generic(GenericFontFamily::UiSansSerif)
    }

    /// Alternative monospace font for user interfaces.
    pub const fn ui_monospace() -> Self {
        Self::Generic(GenericFontFamily::UiMonospace)
    }

    /// Fonts that have rounded features.
    pub const fn ui_rounded() -> Self {
        Self::Generic(GenericFontFamily::UiRounded)
    }

    /// Fonts that are specifically designed to render emoji.
    pub const fn emoji() -> Self {
        Self::Generic(GenericFontFamily::Emoji)
    }

    /// This is for the particular stylistic concerns of representing
    /// mathematics: superscript and subscript, brackets that cross several
    /// lines, nesting expressions, and double struck glyphs with distinct
    /// meanings.
    pub const fn math() -> Self {
        Self::Generic(GenericFontFamily::Math)
    }

    /// A particular style of Chinese characters that are between serif-style
    /// Song and cursive-style Kai forms. This style is often used for
    /// government documents.
    pub const fn fang_song() -> Self {
        Self::Generic(GenericFontFamily::FangSong)
    }

    /// Returns true if the `FontSource` is a list-like source (either the `Families` or `List` variant).
    pub const fn is_list_like(&self) -> bool {
        matches!(self, FontSource::Families(_) | FontSource::List(_))
    }

    /// Returns true if this `FontSource` is a `List` that contains at least one list-like source.
    pub fn is_recursive(&self) -> bool {
        match self {
            FontSource::List(font_sources) => font_sources.iter().any(Self::is_list_like),
            _ => false,
        }
    }

    /// Resolve the [`FontSource`] to a Parley [`FontFamily`].
    pub fn resolve_font_family<'a>(
        &'a self,
        fonts: &'a Assets<Font>,
    ) -> Result<FontFamily<'a>, TextError> {
        Ok(match self {
            FontSource::Handle(handle) => {
                FontFamily::Single(parley::FontFamilyName::Named(Cow::Borrowed(
                    fonts
                        .get(handle.id())
                        .ok_or(TextError::NoSuchFont)?
                        .alias
                        .as_str(),
                )))
            }
            FontSource::Family(family) => FontFamily::named(family.as_str()),
            FontSource::Families(source) => FontFamily::Source(Cow::Borrowed(source.as_str())),
            FontSource::List(_) => {
                let font_sources = self.flatten();
                match font_sources.as_slice() {
                    [] => FontFamily::List(Cow::Owned(Vec::new())),
                    [source] => match *source {
                        FontSource::Handle(handle) => {
                            FontFamily::Single(parley::FontFamilyName::Named(Cow::Borrowed(
                                fonts
                                    .get(handle.id())
                                    .ok_or(TextError::NoSuchFont)?
                                    .alias
                                    .as_str(),
                            )))
                        }
                        FontSource::Family(family) => FontFamily::Single(
                            parley::FontFamilyName::Named(Cow::Borrowed(family.as_str())),
                        ),
                        FontSource::Families(source) => {
                            FontFamily::Source(Cow::Borrowed(source.as_str()))
                        }
                        FontSource::Generic(generic_family) => {
                            #[cfg(not(feature = "system_font_discovery"))]
                            bevy_log::error_once!( "A generic FontSource ({generic_family:?}) was used, but the `system_font_discovery` \
                            feature is not enabled. Text may not render. Enable the feature to allow Bevy \
                            to discover system fonts.");
                            FontFamily::Single(parley::FontFamilyName::Generic(
                                (*generic_family).into(),
                            ))
                        }
                        FontSource::List(_) => {
                            unreachable!("FontSource::flatten should not return lists")
                        }
                    },
                    _ => {
                        let mut families = Vec::new();
                        for source in font_sources.iter().copied() {
                            match source {
                                FontSource::Handle(handle) => {
                                    families.push(parley::FontFamilyName::Named(Cow::Borrowed(
                                        fonts
                                            .get(handle.id())
                                            .ok_or(TextError::NoSuchFont)?
                                            .alias
                                            .as_str(),
                                    )));
                                }
                                FontSource::Family(family) => {
                                    families.push(parley::FontFamilyName::Named(Cow::Borrowed(
                                        family.as_str(),
                                    )));
                                }
                                FontSource::Families(source) => {
                                    families.extend(
                                        parley::FontFamilyName::parse_css_list(source.as_str())
                                            .map_while(Result::ok),
                                    );
                                }
                                FontSource::List(_) => {
                                    unreachable!("FontSource::flatten should not return lists")
                                }
                                FontSource::Generic(generic_family) => {
                                    #[cfg(not(feature = "system_font_discovery"))]
                                    bevy_log::error_once!( "A generic FontSource ({generic_family:?}) was used, but the `system_font_discovery` \
                                    feature is not enabled. Text may not render. Enable the feature to allow Bevy \
                                    to discover system fonts.");
                                    families.push(parley::FontFamilyName::Generic(
                                        (*generic_family).into(),
                                    ));
                                }
                            }
                        }
                        FontFamily::List(Cow::Owned(families))
                    }
                }
            }
            FontSource::Generic(generic_family) => {
                #[cfg(not(feature = "system_font_discovery"))]
                bevy_log::error_once!( "A generic FontSource ({generic_family:?}) was used, but the `system_font_discovery` \
                feature is not enabled. Text may not render. Enable the feature to allow Bevy \
                to discover system fonts.");
                FontFamily::Single(parley::FontFamilyName::Generic((*generic_family).into()))
            }
        })
    }
}

impl Default for FontSource {
    fn default() -> Self {
        Self::Handle(Handle::default())
    }
}

impl From<Handle<Font>> for FontSource {
    fn from(handle: Handle<Font>) -> Self {
        Self::Handle(handle)
    }
}

impl From<&Handle<Font>> for FontSource {
    fn from(handle: &Handle<Font>) -> Self {
        Self::Handle(handle.clone())
    }
}

impl From<SmolStr> for FontSource {
    fn from(families: SmolStr) -> Self {
        FontSource::Families(families)
    }
}

impl From<&str> for FontSource {
    fn from(families: &str) -> Self {
        FontSource::Families(families.into())
    }
}

impl From<GenericFontFamily> for FontSource {
    fn from(generic: GenericFontFamily) -> Self {
        Self::Generic(generic)
    }
}

impl From<Vec<FontSource>> for FontSource {
    fn from(list: Vec<FontSource>) -> Self {
        Self::List(list)
    }
}

impl<const N: usize> From<[FontSource; N]> for FontSource {
    fn from(list: [FontSource; N]) -> Self {
        Self::List(list.into())
    }
}

/// Generic font families that are resolved through Parley's font database.
#[derive(Default, Clone, Copy, Debug, Reflect, PartialEq, Eq, Hash)]
#[repr(u8)]
pub enum GenericFontFamily {
    /// Fonts with serifs — small decorative strokes at the ends of letterforms.
    ///
    /// Serif fonts are typically used for long passages of text and represent
    /// a more traditional or formal typographic style.
    #[default]
    Serif,
    /// Fonts without serifs.
    ///
    /// Sans-serif fonts generally have low stroke contrast and plain stroke
    /// endings, making them common for UI text and on-screen reading.
    SansSerif,
    /// Fonts that use a cursive or handwritten style.
    ///
    /// Glyphs often resemble connected or flowing pen or brush strokes rather
    /// than printed letterforms.
    Cursive,
    /// Decorative or expressive fonts.
    ///
    /// Fantasy fonts are primarily intended for display purposes and may
    /// prioritize visual style over readability.
    Fantasy,
    /// Fonts in which all glyphs have the same fixed advance width.
    ///
    /// Monospace fonts are commonly used for code, tabular data, and text
    /// where vertical alignment is important.
    Monospace,
    /// The default user interface system font.
    SystemUi,
    /// Alternative serif font for user interfaces.
    UiSerif,
    /// Alternative sans-serif font for user interfaces.
    UiSansSerif,
    /// Alternative monospace font for user interfaces.
    UiMonospace,
    /// Fonts that have rounded features.
    UiRounded,
    /// Fonts that are specifically designed to render emoji.
    Emoji,
    /// This is for the particular stylistic concerns of representing
    /// mathematics: superscript and subscript, brackets that cross several
    /// lines, nesting expressions, and double struck glyphs with distinct
    /// meanings.
    Math,
    /// A particular style of Chinese characters that are between serif-style
    /// Song and cursive-style Kai forms. This style is often used for
    /// government documents.
    FangSong,
}

impl From<GenericFontFamily> for parley::GenericFamily {
    fn from(generic: GenericFontFamily) -> Self {
        match generic {
            GenericFontFamily::Serif => Self::Serif,
            GenericFontFamily::SansSerif => Self::SansSerif,
            GenericFontFamily::Cursive => Self::Cursive,
            GenericFontFamily::Fantasy => Self::Fantasy,
            GenericFontFamily::Monospace => Self::Monospace,
            GenericFontFamily::SystemUi => Self::SystemUi,
            GenericFontFamily::UiSerif => Self::UiSerif,
            GenericFontFamily::UiSansSerif => Self::UiSansSerif,
            GenericFontFamily::UiMonospace => Self::UiMonospace,
            GenericFontFamily::UiRounded => Self::UiRounded,
            GenericFontFamily::Emoji => Self::Emoji,
            GenericFontFamily::Math => Self::Math,
            GenericFontFamily::FangSong => Self::FangSong,
        }
    }
}

/// `TextFont` determines the style of a text span within a [`ComputedTextBlock`], specifically
/// the font face, the font size, the line height, and the antialiasing method.
#[derive(Component, Clone, Debug, Reflect, PartialEq, FromTemplate)]
#[reflect(Component, Default, Debug, Clone)]
pub struct TextFont {
    /// Specifies the font face used for this text section.
    ///
    /// A `FontSource` can be a handle to a font asset, a font family name,
    /// a CSS font-family list, an ordered family list, or a generic font category
    /// that is resolved using Parley's
    /// [`FontContext`](`parley::FontContext`) which is accessible through the
    /// [`FontCx`](`crate::FontCx`) resource.
    pub font: FontSource,
    /// The vertical height of rasterized glyphs in the font atlas in pixels.
    ///
    /// This is multiplied by the window scale factor and `UiScale`, but not the text entity's
    /// transform or camera projection. Then, the scaled font size is rounded to the nearest pixel
    /// to produce the final font size used during glyph layout.
    ///
    /// A new font atlas is generated for every combination of font handle and scaled font size
    /// which can have a strong performance impact.
    pub font_size: FontSize,
    /// How thick or bold the strokes of a font appear.
    ///
    /// Font weights can be any value between 1 and 1000, inclusive.
    ///
    /// Only supports variable weight fonts.
    pub weight: FontWeight,
    /// How condensed or expanded the glyphs appear horizontally.
    pub width: FontWidth,
    /// The slant style of a font face: normal, italic, or oblique.
    pub style: FontStyle,
    /// The antialiasing method to use when rendering text.
    pub font_smoothing: FontSmoothing,
    /// OpenType features for .otf fonts that support them.
    pub font_features: FontFeatures,
    /// OpenType variations for variable fonts that support them.
    pub font_variations: FontVariations,
}

impl TextFont {
    /// Returns a new [`TextFont`] with the specified font size.
    pub fn from_font_size(font_size: impl Into<FontSize>) -> Self {
        Self::default().with_font_size(font_size)
    }

    /// Returns a new [`TextFont`] with the specified font weight
    pub fn from_font_weight(weight: impl Into<FontWeight>) -> Self {
        Self::default().with_font_weight(weight)
    }

    /// Returns this [`TextFont`] with the specified font face handle.
    pub fn with_font(mut self, font: Handle<Font>) -> Self {
        self.font = FontSource::Handle(font);
        self
    }

    /// Returns this [`TextFont`] with the specified font family.
    pub fn with_family(mut self, family: impl Into<SmolStr>) -> Self {
        self.font = FontSource::Family(family.into());
        self
    }

    /// Returns this [`TextFont`] with the specified font size.
    pub fn with_font_size(mut self, font_size: impl Into<FontSize>) -> Self {
        self.font_size = font_size.into();
        self
    }

    /// Returns this [`TextFont`] with the specified [`FontSmoothing`].
    pub const fn with_font_smoothing(mut self, font_smoothing: FontSmoothing) -> Self {
        self.font_smoothing = font_smoothing;
        self
    }

    /// Returns this [`TextFont`] with the specified [`FontWeight`].
    pub fn with_font_weight(mut self, weight: impl Into<FontWeight>) -> Self {
        self.weight = weight.into();
        self
    }
}

impl<T: Into<FontSource>> From<T> for TextFont {
    fn from(source: T) -> Self {
        Self {
            font: source.into(),
            ..default()
        }
    }
}

impl Default for TextFont {
    fn default() -> Self {
        Self {
            font: Default::default(),
            font_size: FontSize::Rem(1.),
            style: FontStyle::Normal,
            weight: FontWeight::NORMAL,
            width: FontWidth::NORMAL,
            font_features: FontFeatures::default(),
            font_variations: FontVariations::default(),
            font_smoothing: Default::default(),
        }
    }
}

/// The vertical height of rasterized glyphs in the font atlas in pixels.
///
/// This is multiplied by the scale factor, but not the text entity
/// transform or camera projection.
///
/// The viewport variants are not supported by `Text2d`.
///
/// A new font atlas is generated for every combination of font handle and scaled font size
/// which can have a strong performance impact.
#[derive(Component, Copy, Clone, Debug, Reflect)]
pub enum FontSize {
    /// Font Size in logical pixels.
    Px(f32),
    /// Font size as a percentage of the viewport width.
    Vw(f32),
    /// Font size as a percentage of the viewport height.
    Vh(f32),
    /// Font size as a percentage of the smaller of the viewport width and height.
    VMin(f32),
    /// Font size as a percentage of the larger of the viewport width and height.
    VMax(f32),
    /// Font Size relative to the value of the `RemSize` resource.
    Rem(f32),
}

impl FontSize {
    /// Evaluate the font size to a value in logical pixels
    pub fn eval(
        self,
        // Viewport size in logical pixels
        logical_viewport_size: Vec2,
        // Base Rem size in logical pixels
        rem_size: RemSize,
    ) -> f32 {
        match self {
            FontSize::Px(s) => s,
            FontSize::Vw(s) => logical_viewport_size.x * s / 100.,
            FontSize::Vh(s) => logical_viewport_size.y * s / 100.,
            FontSize::VMin(s) => logical_viewport_size.min_element() * s / 100.,
            FontSize::VMax(s) => logical_viewport_size.max_element() * s / 100.,
            FontSize::Rem(s) => rem_size.0 * s,
        }
    }
}

impl PartialEq for FontSize {
    fn eq(&self, other: &Self) -> bool {
        match (*self, *other) {
            (Self::Px(l), Self::Px(r))
            | (Self::Vw(l), Self::Vw(r))
            | (Self::Vh(l), Self::Vh(r))
            | (Self::VMin(l), Self::VMin(r))
            | (Self::VMax(l), Self::VMax(r))
            | (Self::Rem(l), Self::Rem(r)) => l == r,
            _ => false,
        }
    }
}

impl core::ops::Mul<f32> for FontSize {
    type Output = FontSize;

    fn mul(self, rhs: f32) -> Self::Output {
        match self {
            FontSize::Px(v) => FontSize::Px(v * rhs),
            FontSize::Vw(v) => FontSize::Vw(v * rhs),
            FontSize::Vh(v) => FontSize::Vh(v * rhs),
            FontSize::VMin(v) => FontSize::VMin(v * rhs),
            FontSize::VMax(v) => FontSize::VMax(v * rhs),
            FontSize::Rem(v) => FontSize::Rem(v * rhs),
        }
    }
}

impl core::ops::Mul<FontSize> for f32 {
    type Output = FontSize;

    fn mul(self, rhs: FontSize) -> Self::Output {
        rhs * self
    }
}

impl Default for FontSize {
    fn default() -> Self {
        Self::Px(20.)
    }
}

impl From<f32> for FontSize {
    fn from(value: f32) -> Self {
        Self::Px(value)
    }
}

/// Default [`RemSize`] and [`EmSize`], in logical pixels
pub const DEFAULT_REM_SIZE_PX: f32 = 20.0;

/// The root font size, in logical pixels.
///
/// `Rem` units always resolve against this one global resource, including
/// `FontSize::Rem`, `LetterSpacing::Rem` and `Val::Rem`.
#[derive(Resource, Copy, Clone, Debug, PartialEq, Deref, DerefMut, Reflect)]
pub struct RemSize(pub f32);

impl Default for RemSize {
    fn default() -> Self {
        Self(DEFAULT_REM_SIZE_PX)
    }
}

/// The font size, in logical pixels, used to resolve `Val::Em` values in a UI node.
///
/// `Em` units are relative to the font size of the node they sit on, and this is that
/// font size made concrete. Required by `Node`, so every UI node has one.
///
/// If the node has a `TextFont`, the `EmSize` is derived from it whenever the `TextFont`,
/// `RemSize` or render-target info changes; until then any value you place on it persists.
/// If it does not have a `TextFont`, the value is yours to set, for example by an app-level
/// propagation system. `EmSize` defaults to [`DEFAULT_REM_SIZE_PX`], which matches the default
/// [`RemSize`] but does not track changes to it. Use `Val::Rem` instead for values that
/// should follow the root font size.
///
/// Removing a `TextFont` leaves the last derived value in place.
#[derive(Debug, PartialEq, Clone, Copy, Reflect, Component)]
#[reflect(Default, PartialEq, Debug, Clone, Component)]
pub struct EmSize(pub f32);

impl Default for EmSize {
    fn default() -> Self {
        EmSize(DEFAULT_REM_SIZE_PX)
    }
}

impl EmSize {
    /// Resolves a [`FontSize`] to a concrete [`EmSize`] in logical pixels.
    pub fn from_font_size(
        font_size: FontSize,
        logical_viewport_size: Vec2,
        rem_size: RemSize,
    ) -> Self {
        EmSize(font_size.eval(logical_viewport_size, rem_size))
    }
}

/// How thick or bold the strokes of a font appear.
///
/// Valid font weights range from 1 to 1000, inclusive.
/// Weights above 1000 are clamped to 1000.
/// A weight of 0 is treated as [`FontWeight::DEFAULT`].
///
/// Legacy names from when most fonts weren't variable fonts
/// are included as const values, but are misleading if
/// used in documentation and examples, as valid weights
/// for variable fonts are all of the numbers from 1-1000, and
/// not all fonts which are not variable fonts have those weights
/// supplied. If you use a custom font that supplies only specific
/// weights, that will be documented where you purchased the font.
///
/// `<https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/font-weight>`
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Reflect)]
pub struct FontWeight(pub u16);

impl FontWeight {
    /// Weight 100.
    pub const THIN: FontWeight = FontWeight(100);

    /// Weight 200.
    pub const EXTRA_LIGHT: FontWeight = FontWeight(200);

    /// Weight 300.
    pub const LIGHT: FontWeight = FontWeight(300);

    /// Weight 400.
    pub const NORMAL: FontWeight = FontWeight(400);

    /// Weight 500.
    pub const MEDIUM: FontWeight = FontWeight(500);

    /// Weight 600.
    pub const SEMIBOLD: FontWeight = FontWeight(600);

    /// Weight 700.
    pub const BOLD: FontWeight = FontWeight(700);

    /// Weight 800
    pub const EXTRA_BOLD: FontWeight = FontWeight(800);

    /// Weight 900.
    pub const BLACK: FontWeight = FontWeight(900);

    /// Weight 950.
    pub const EXTRA_BLACK: FontWeight = FontWeight(950);

    /// The default font weight.
    pub const DEFAULT: FontWeight = Self::NORMAL;

    /// Clamp the weight value to between 1 and 1000.
    /// Values of 0 are mapped to `Weight::DEFAULT`.
    pub const fn clamp(mut self) -> Self {
        if self.0 == 0 {
            self = Self::DEFAULT;
        } else if 1000 < self.0 {
            self.0 = 1000;
        }
        Self(self.0)
    }
}

impl Default for FontWeight {
    fn default() -> Self {
        Self::DEFAULT
    }
}

impl From<FontWeight> for parley::style::FontWeight {
    fn from(value: FontWeight) -> Self {
        parley::style::FontWeight::new(value.clamp().0 as f32)
    }
}

/// The visual width of a font as a ratio of its normal width, typically 0.5 to 2.0.
/// `<https://docs.microsoft.com/en-us/typography/opentype/spec/os2#uswidthclass>`
#[derive(Clone, Copy, PartialEq, PartialOrd, Debug, Reflect)]
pub struct FontWidth(pub f32);

impl FontWidth {
    /// 50% of normal width.
    pub const ULTRA_CONDENSED: Self = Self(0.5);

    /// 62.5% of normal width.
    pub const EXTRA_CONDENSED: Self = Self(0.625);

    /// 75% of normal width.
    pub const CONDENSED: Self = Self(0.75);

    /// 87.5% of normal width.
    pub const SEMI_CONDENSED: Self = Self(0.875);

    /// 100% of normal width. This is the default.
    pub const NORMAL: Self = Self(1.0);

    /// 112.5% of normal width.
    pub const SEMI_EXPANDED: Self = Self(1.125);

    /// 125% of normal width.
    pub const EXPANDED: Self = Self(1.25);

    /// 150% of normal width.
    pub const EXTRA_EXPANDED: Self = Self(1.5);

    /// 200% of normal width.
    pub const ULTRA_EXPANDED: Self = Self(2.0);
}

impl Default for FontWidth {
    fn default() -> Self {
        Self::NORMAL
    }
}

impl From<FontWidth> for parley::FontWidth {
    fn from(value: FontWidth) -> Self {
        parley::FontWidth::from_ratio(value.0)
    }
}

/// The slant style of a font face: normal, italic, or oblique.
#[derive(Clone, Copy, Default, PartialEq, Debug, Reflect)]
pub enum FontStyle {
    /// A face that is neither italic nor obliqued.
    #[default]
    Normal,
    /// A form that is generally cursive in nature.
    Italic,
    /// A typically sloped version of the regular face.
    ///
    /// The contained `f32` is the slant angle of the text, in degrees.
    Oblique(Option<f32>),
}

impl From<FontStyle> for parley::FontStyle {
    fn from(value: FontStyle) -> Self {
        match value {
            FontStyle::Normal => parley::FontStyle::Normal,
            FontStyle::Italic => parley::FontStyle::Italic,
            FontStyle::Oblique(value) => parley::FontStyle::Oblique(value),
        }
    }
}

/// An OpenType font feature tag.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Reflect)]
pub struct FontFeatureTag([u8; 4]);

impl FontFeatureTag {
    /// Replaces character combinations like fi, fl with ligatures.
    pub const STANDARD_LIGATURES: FontFeatureTag = FontFeatureTag::new(b"liga");

    /// Enables ligatures based on character context.
    pub const CONTEXTUAL_LIGATURES: FontFeatureTag = FontFeatureTag::new(b"clig");

    /// Enables optional ligatures for stylistic use (e.g., ct, st).
    pub const DISCRETIONARY_LIGATURES: FontFeatureTag = FontFeatureTag::new(b"dlig");

    /// Adjust glyph shapes based on surrounding letters.
    pub const CONTEXTUAL_ALTERNATES: FontFeatureTag = FontFeatureTag::new(b"calt");

    /// Use alternate glyph designs.
    pub const STYLISTIC_ALTERNATES: FontFeatureTag = FontFeatureTag::new(b"salt");

    /// Replaces lowercase letters with small caps.
    pub const SMALL_CAPS: FontFeatureTag = FontFeatureTag::new(b"smcp");

    /// Replaces uppercase letters with small caps.
    pub const CAPS_TO_SMALL_CAPS: FontFeatureTag = FontFeatureTag::new(b"c2sc");

    /// Replaces characters with swash versions (often decorative).
    pub const SWASH: FontFeatureTag = FontFeatureTag::new(b"swsh");

    /// Enables alternate glyphs for large sizes or titles.
    pub const TITLING_ALTERNATES: FontFeatureTag = FontFeatureTag::new(b"titl");

    /// Converts numbers like 1/2 into true fractions (½).
    pub const FRACTIONS: FontFeatureTag = FontFeatureTag::new(b"frac");

    /// Formats characters like 1st, 2nd properly.
    pub const ORDINALS: FontFeatureTag = FontFeatureTag::new(b"ordn");

    /// Uses a slashed version of zero (0) to differentiate from O.
    pub const SLASHED_ZERO: FontFeatureTag = FontFeatureTag::new(b"zero");

    /// Replaces figures with superscript figures, e.g. for indicating footnotes.
    pub const SUPERSCRIPT: FontFeatureTag = FontFeatureTag::new(b"sups");

    /// Replaces figures with subscript figures.
    pub const SUBSCRIPT: FontFeatureTag = FontFeatureTag::new(b"subs");

    /// Changes numbers to "oldstyle" form, which fit better in the flow of sentences or other text.
    pub const OLDSTYLE_FIGURES: FontFeatureTag = FontFeatureTag::new(b"onum");

    /// Changes numbers to "lining" form, which are better suited for standalone numbers. When
    /// enabled, the bottom of all numbers will be aligned with each other.
    pub const LINING_FIGURES: FontFeatureTag = FontFeatureTag::new(b"lnum");

    /// Changes numbers to be of proportional width. When enabled, numbers may have varying widths.
    pub const PROPORTIONAL_FIGURES: FontFeatureTag = FontFeatureTag::new(b"pnum");

    /// Changes numbers to be of uniform (tabular) width. When enabled, all numbers will have the
    /// same width.
    pub const TABULAR_FIGURES: FontFeatureTag = FontFeatureTag::new(b"tnum");

    /// Varies the stroke thickness. Valid values are in the range of 1 to 1000, inclusive.
    pub const WEIGHT: FontFeatureTag = FontFeatureTag::new(b"wght");

    /// Varies the width of text from narrower to wider. Must be a value greater than 0. A value of
    /// 100 is typically considered standard width.
    pub const WIDTH: FontFeatureTag = FontFeatureTag::new(b"wdth");

    /// Varies between upright and slanted text. Must be a value greater than -90 and less than +90.
    /// A value of 0 is upright.
    pub const SLANT: FontFeatureTag = FontFeatureTag::new(b"slnt");

    /// Create a new [`FontFeatureTag`] from raw bytes.
    pub const fn new(src: &[u8; 4]) -> Self {
        Self(*src)
    }
}

impl Debug for FontFeatureTag {
    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
        // OpenType tags are always ASCII, so this match will succeed for valid tags. This gives us
        // human-readable debug output, e.g. FontFeatureTag("liga").
        match from_utf8(&self.0) {
            Ok(s) => write!(f, "FontFeatureTag(\"{}\")", s),
            Err(_) => write!(f, "FontFeatureTag({:?})", self.0),
        }
    }
}

/// OpenType features for .otf fonts that support them.
///
/// Examples features include ligatures, small-caps, and fractional number display. For the complete
/// list of OpenType features, see the spec at
/// `<https://learn.microsoft.com/en-us/typography/opentype/spec/featurelist>`.
///
/// # Usage:
/// ```
/// use bevy_text::{FontFeatureTag, FontFeatures};
///
/// // Create using the builder
/// let font_features = FontFeatures::builder()
///   .enable(FontFeatureTag::STANDARD_LIGATURES)
///   .set(FontFeatureTag::WEIGHT, 300)
///   .build();
///
/// // Create from a list
/// let more_font_features: FontFeatures = [
///   FontFeatureTag::STANDARD_LIGATURES,
///   FontFeatureTag::OLDSTYLE_FIGURES,
///   FontFeatureTag::TABULAR_FIGURES
/// ].into();
/// ```
#[derive(Clone, Debug, Default, Reflect, PartialEq)]
pub struct FontFeatures {
    features: Vec<(FontFeatureTag, u32)>,
}

impl FontFeatures {
    /// Create a new [`FontFeaturesBuilder`].
    pub fn builder() -> FontFeaturesBuilder {
        FontFeaturesBuilder::default()
    }
}

/// A builder for [`FontFeatures`].
#[derive(Clone, Default)]
pub struct FontFeaturesBuilder {
    features: Vec<(FontFeatureTag, u32)>,
}

impl FontFeaturesBuilder {
    /// Enable an OpenType feature.
    ///
    /// Most OpenType features are on/off switches, so this is a convenience method that sets the
    /// feature's value to "1" (enabled). For non-boolean features, see [`FontFeaturesBuilder::set`].
    pub fn enable(self, feature_tag: FontFeatureTag) -> Self {
        self.set(feature_tag, 1)
    }

    /// Set an OpenType feature to a specific value.
    ///
    /// For most features, the [`FontFeaturesBuilder::enable`] method should be used instead. A few
    /// features, such as "wght", take numeric values, so this method may be used for these cases.
    pub fn set(mut self, feature_tag: FontFeatureTag, value: u32) -> Self {
        self.features.push((feature_tag, value));
        self
    }

    /// Build a [`FontFeatures`] from the values set within this builder.
    pub fn build(self) -> FontFeatures {
        FontFeatures {
            features: self.features,
        }
    }
}

/// Allow [`FontFeatures`] to be built from a list. This is suitable for the standard case when each
/// listed feature is a boolean type. If any features require a numeric value (like "wght"), use
/// [`FontFeaturesBuilder`] instead.
impl<T> From<T> for FontFeatures
where
    T: IntoIterator<Item = FontFeatureTag>,
{
    fn from(value: T) -> Self {
        FontFeatures {
            features: value.into_iter().map(|x| (x, 1)).collect(),
        }
    }
}

impl From<&FontFeatures> for parley::style::FontFeatures<'static> {
    fn from(font_features: &FontFeatures) -> Self {
        parley::style::FontFeatures::List(
            font_features
                .features
                .iter()
                .map(|(tag, value)| FontFeature {
                    tag: Tag::new(&tag.0),
                    value: *value as u16,
                })
                .collect(),
        )
    }
}

/// An OpenType font variation tag.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Reflect)]
pub struct FontVariationTag([u8; 4]);

impl FontVariationTag {
    /// Varies the stroke thickness. The range is typically 1 to 1000.
    pub const WEIGHT: FontVariationTag = FontVariationTag::new(b"wght");

    /// Varies the width of glyphs from narrower to wider. The range is typically 50 to 200 with
    /// 100 being standard width.
    pub const WIDTH: FontVariationTag = FontVariationTag::new(b"wdth");

    /// Varies between upright and slanted glyphs. The range is typically between -90 and +90 degrees,
    /// where 0 is upright.
    pub const SLANT: FontVariationTag = FontVariationTag::new(b"slnt");

    /// Varies the design of glyphs for different optical sizes (physical font size).
    /// The range is typically 6 to 72.
    pub const OPTICAL_SIZE: FontVariationTag = FontVariationTag::new(b"opsz");

    /// Create a new [`FontVariationTag`] from raw bytes.
    pub const fn new(src: &[u8; 4]) -> Self {
        Self(*src)
    }
}

impl Debug for FontVariationTag {
    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
        match from_utf8(&self.0) {
            Ok(s) => write!(f, "FontVariationTag(\"{}\")", s),
            Err(_) => write!(f, "FontVariationTag({:?})", self.0),
        }
    }
}

/// OpenType font variations for variable fonts that support them.
///
/// Variable fonts expose named axes (e.g. `wght`, `FILL`) that accept continuous `f32` values.
/// This is distinct from [`FontFeatures`], which mainly controls on/off OpenType layout features.
///
/// # Usage
/// ```
/// use bevy_text::{FontVariationTag, FontVariations};
///
/// let variations = FontVariations::builder()
///     .set(FontVariationTag::WEIGHT, 400.0)
///     .build();
/// ```
#[derive(Clone, Debug, Default, Reflect, PartialEq)]
pub struct FontVariations {
    variations: Vec<(FontVariationTag, f32)>,
}

impl FontVariations {
    /// Create a new [`FontVariationsBuilder`].
    pub fn builder() -> FontVariationsBuilder {
        FontVariationsBuilder::default()
    }
}

/// A builder for [`FontVariations`].
#[derive(Clone, Default)]
pub struct FontVariationsBuilder {
    variations: Vec<(FontVariationTag, f32)>,
}

impl FontVariationsBuilder {
    /// Set a font variation to a specific value.
    pub fn set(mut self, tag: FontVariationTag, value: f32) -> Self {
        self.variations.push((tag, value));
        self
    }

    /// Build a [`FontVariations`] from the values set within this builder.
    pub fn build(self) -> FontVariations {
        FontVariations {
            variations: self.variations,
        }
    }
}

impl From<&FontVariations> for parley::style::FontVariations<'static> {
    fn from(font_variations: &FontVariations) -> Self {
        parley::style::FontVariations::List(
            font_variations
                .variations
                .iter()
                .map(|(tag, value)| FontVariation {
                    tag: Tag::new(&tag.0),
                    value: *value,
                })
                .collect(),
        )
    }
}

/// Specifies the height of each line of text for `Text` and `Text2d`
///
/// Default is 1.2x the font size
#[derive(Component, Debug, Clone, Copy, PartialEq, Reflect)]
#[reflect(Component, Debug, Clone, PartialEq)]
pub enum LineHeight {
    /// Set line height to a specific number of pixels
    Px(f32),
    /// Set line height to a multiple of the font size
    RelativeToFont(f32),
}

impl LineHeight {
    /// eval a line height
    pub fn eval(self) -> parley::LineHeight {
        match self {
            LineHeight::Px(px) => parley::LineHeight::Absolute(px),
            LineHeight::RelativeToFont(scale) => parley::LineHeight::FontSizeRelative(scale),
        }
    }
}

impl Default for LineHeight {
    fn default() -> Self {
        LineHeight::RelativeToFont(1.2)
    }
}

/// Specifies the space between each letter of text for `Text` and `Text2d`
///
/// Default is 0
#[derive(Component, Debug, Clone, Copy, PartialEq, Reflect)]
#[reflect(Component, Default, Debug, Clone, PartialEq)]
pub enum LetterSpacing {
    /// Set letter spacing to a specific number of logical pixels
    Px(f32),
    /// Set letter spacing to a multiple of the root font size ([`RemSize`])
    Rem(f32),
}

impl LetterSpacing {
    /// Evaluate a [`LetterSpacing`] into logical pixels either
    /// because it specifies them directly or using the global
    /// [`RemSize`] resource.
    pub(crate) fn eval(self, rem_size: RemSize) -> f32 {
        match self {
            LetterSpacing::Px(px) => px,
            LetterSpacing::Rem(rem) => rem * rem_size.0,
        }
    }
}

impl Default for LetterSpacing {
    fn default() -> Self {
        Self::Px(0.0)
    }
}

/// The color of the text for this section.
#[derive(Component, Copy, Clone, Debug, Deref, DerefMut, Reflect, PartialEq)]
#[reflect(Component, Default, Debug, PartialEq, Clone)]
pub struct TextColor(pub Color);

impl Default for TextColor {
    fn default() -> Self {
        Self::WHITE
    }
}

impl<T: Into<Color>> From<T> for TextColor {
    fn from(color: T) -> Self {
        Self(color.into())
    }
}

impl TextColor {
    /// Black colored text
    pub const BLACK: Self = TextColor(Color::BLACK);
    /// White colored text
    pub const WHITE: Self = TextColor(Color::WHITE);
}

/// The background color of the text for this section.
#[derive(Component, Copy, Clone, Debug, Deref, DerefMut, Reflect, PartialEq)]
#[reflect(Component, Default, Debug, PartialEq, Clone)]
pub struct TextBackgroundColor(pub Color);

impl Default for TextBackgroundColor {
    fn default() -> Self {
        Self(Color::BLACK)
    }
}

impl<T: Into<Color>> From<T> for TextBackgroundColor {
    fn from(color: T) -> Self {
        Self(color.into())
    }
}

impl TextBackgroundColor {
    /// Black background
    pub const BLACK: Self = TextBackgroundColor(Color::BLACK);
    /// White background
    pub const WHITE: Self = TextBackgroundColor(Color::WHITE);
}

/// Determines how lines will be broken when preventing text from running out of bounds.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default, Reflect, Serialize, Deserialize)]
#[reflect(Serialize, Deserialize, Clone, PartialEq, Hash, Default)]
pub enum LineBreak {
    /// Uses the [Unicode Line Breaking Algorithm](https://www.unicode.org/reports/tr14/).
    /// Lines will be broken up at the nearest suitable word boundary, usually a space.
    /// This behavior suits most cases, as it keeps words intact across linebreaks.
    #[default]
    WordBoundary,
    /// Lines will be broken without discrimination on any character that would leave bounds.
    /// This is closer to the behavior one might expect from text in a terminal.
    /// However it may lead to words being broken up across linebreaks.
    AnyCharacter,
    /// Wraps at the word level, or fallback to character level if a word can’t fit on a line by itself
    WordOrCharacter,
    /// No soft wrapping, where text is automatically broken up into separate lines when it overflows a boundary, will ever occur.
    /// Hard wrapping, where text contains an explicit linebreak such as the escape sequence `\n`, is still enabled.
    NoWrap,
}

/// A text entity with this component is drawn with strikethrough.
#[derive(Component, Copy, Clone, Debug, Reflect, Default, Serialize, Deserialize)]
#[reflect(Serialize, Deserialize, Clone, Default)]
pub struct Strikethrough;

/// Color for the text's strikethrough. If this component is not present, its `TextColor` will be used.
#[derive(Component, Copy, Clone, Debug, Deref, DerefMut, Reflect, PartialEq)]
#[reflect(Component, Default, Debug, PartialEq, Clone)]
pub struct StrikethroughColor(pub Color);

impl Default for StrikethroughColor {
    fn default() -> Self {
        Self(Color::WHITE)
    }
}

impl<T: Into<Color>> From<T> for StrikethroughColor {
    fn from(color: T) -> Self {
        Self(color.into())
    }
}

/// Add to a text entity to draw its text with underline.
#[derive(Component, Copy, Clone, Debug, Reflect, Default, Serialize, Deserialize)]
#[reflect(Serialize, Deserialize, Clone, Default)]
pub struct Underline;

/// Color for the text's underline. If this component is not present, its `TextColor` will be used.
#[derive(Component, Copy, Clone, Debug, Deref, DerefMut, Reflect, PartialEq)]
#[reflect(Component, Default, Debug, PartialEq, Clone)]
pub struct UnderlineColor(pub Color);

impl Default for UnderlineColor {
    fn default() -> Self {
        Self(Color::WHITE)
    }
}

impl<T: Into<Color>> From<T> for UnderlineColor {
    fn from(color: T) -> Self {
        Self(color.into())
    }
}

/// Determines which antialiasing method to use when rendering text. By default, text is
/// rendered with grayscale antialiasing, but this can be changed to achieve a pixelated look.
///
/// **Note:** Subpixel antialiasing is not currently supported.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default, Reflect, Serialize, Deserialize)]
#[reflect(Serialize, Deserialize, Clone, PartialEq, Hash, Default)]
#[doc(alias = "antialiasing")]
#[doc(alias = "pixelated")]
pub enum FontSmoothing {
    /// No antialiasing. Useful for when you want to render text with a pixel art aesthetic.
    ///
    /// Combine this with `UiAntiAlias::Off` and `Msaa::Off` on your 2D camera for a fully pixelated look.
    ///
    /// **Note:** Due to limitations of the underlying text rendering library,
    /// this may require specially-crafted pixel fonts to look good, especially at small sizes.
    None,
    /// The default grayscale antialiasing. Produces text that looks smooth,
    /// even at small font sizes and low resolutions with modern vector fonts.
    #[default]
    AntiAliased,
    // TODO: Add subpixel antialias support
    // SubpixelAntiAliased,
}

#[derive(Component, Debug, Copy, Clone, Default, Reflect, PartialEq, Hash, Eq)]
#[reflect(Component, Default, Debug, Clone, PartialEq)]
/// Font hinting strategy, which controls the rasterization for fonts.
///
/// Font hinting specializes the vector outlines to make them more clearer / more legible at a specific font size.
/// It is particularly noticeable with small text and low resolutions.
pub enum FontHinting {
    #[default]
    /// Glyphs are rasterized without hinting.
    Disabled,
    /// Glyphs are rasterized with hinting.
    Enabled,
}

impl FontHinting {
    /// Returns true if font hinting is enabled.
    pub fn is_enabled(self) -> bool {
        matches!(self, FontHinting::Enabled)
    }
}

/// System that detects changes to text blocks and sets `ComputedTextBlock::should_rerender`.
///
/// Does not check root text components (e.g. `Text`/`Text2d`) for changes. Their systems must handle change detection.
pub fn detect_text_needs_rerender(
    changed_roots: Query<
        Entity,
        (
            Or<(
                Changed<TextFont>,
                Changed<TextLayout>,
                Changed<LineHeight>,
                Changed<LetterSpacing>,
                Changed<Children>,
            )>,
            With<TextFont>,
            With<TextLayout>,
        ),
    >,
    changed_spans: Query<
        (Entity, Option<&ChildOf>, Has<TextLayout>),
        (
            Or<(
                Changed<TextSpan>,
                Changed<InlineBox>,
                Changed<TextFont>,
                Changed<LineHeight>,
                Changed<LetterSpacing>,
                Changed<Children>,
                Changed<ChildOf>, // Included to detect broken text block hierarchies.
                Added<TextLayout>,
            )>,
            Or<((With<TextSpan>, With<TextFont>), With<InlineBox>)>,
        ),
    >,
    mut computed: Query<(
        Option<&ChildOf>,
        Option<&mut ComputedTextBlock>,
        Has<TextSpan>,
    )>,
) {
    // Root entity:
    // - Root component changed.
    // - TextFont on root changed.
    // - TextLayout changed.
    // - Root children changed (can include additions and removals).
    for root in changed_roots.iter() {
        let Ok((_, Some(mut computed), _)) = computed.get_mut(root) else {
            once!(warn!("found entity {} with a root text component but no ComputedTextBlock; this warning only \
                prints once", root));
            continue;
        };
        computed.needs_rerender = true;
    }

    // Span entity:
    // - Span component changed.
    // - Span TextFont changed.
    // - Span children changed (can include additions and removals).
    for (entity, maybe_span_child_of, has_text_block) in changed_spans.iter() {
        if has_text_block {
            once!(warn!("found entity {} with a TextSpan or InlineBox that has a TextLayout, which should only be on root \
                text entities; this warning only prints once",
                entity));
        }

        let Some(span_child_of) = maybe_span_child_of else {
            once!(warn!(
                "found entity {} with a TextSpan or InlineBox that has no parent; it should have an ancestor \
                with a root text component; this warning only prints once",
                entity
            ));
            continue;
        };
        let mut parent: Entity = span_child_of.parent();

        // Search for the nearest ancestor with ComputedTextBlock.
        // Note: We assume the perf cost from duplicate visits in the case that multiple spans in a block are visited
        // is outweighed by the expense of tracking visited spans.
        loop {
            let Ok((maybe_child_of, maybe_computed, has_span)) = computed.get_mut(parent) else {
                once!(warn!("found entity {} with a TextSpan or InlineBox that is part of a broken hierarchy with a ChildOf \
                    component that points at non-existent entity {}; this warning only prints once",
                    entity, parent));
                break;
            };
            if let Some(mut computed) = maybe_computed {
                computed.needs_rerender = true;
                break;
            }
            if !has_span {
                once!(warn!("found entity {} with a TextSpan or InlineBox that has an ancestor ({}) that does not have a text \
                span component or a ComputedTextBlock component; this warning only prints once",
                    entity, parent));
                break;
            }
            let Some(next_child_of) = maybe_child_of else {
                once!(warn!(
                    "found entity {} with a TextSpan or InlineBox that has no ancestor with the root text \
                    component; this warning only prints once",
                    entity
                ));
                break;
            };
            parent = next_child_of.parent();
        }
    }
}

#[cfg(test)]
mod tests {
    use bevy_asset::Assets;

    use crate::Font;

    use super::*;

    #[test]
    fn flattening_single_font_source_returns_source() {
        let source = FontSource::Family("Fira Mono".into());

        assert_eq!(source.flatten().into_iter().collect::<Vec<_>>(), [&source]);
    }

    #[test]
    fn flattening_lists_preserves_list_order() {
        let list = vec![
            FontSource::family("Fira Mono"),
            FontSource::sans_serif(),
            FontSource::families("Garamond, Mona Sans"),
        ];

        assert_eq!(
            FontSource::List(list.clone())
                .flatten()
                .into_iter()
                .cloned()
                .collect::<Vec<_>>(),
            list
        );
    }

    #[test]
    fn font_source_flatten_recursively_flattens_lists() {
        let source = FontSource::list([
            FontSource::family("Fira Sans"),
            FontSource::List(vec![
                FontSource::emoji(),
                FontSource::List(Vec::new()),
                FontSource::families("Mona Sans, Garamond"),
                FontSource::List(vec![FontSource::fantasy(), FontSource::ui_monospace()]),
            ]),
            FontSource::family("Fira Mono"),
        ]);

        assert_eq!(
            source.flatten().into_iter().cloned().collect::<Vec<_>>(),
            [
                FontSource::Family("Fira Sans".into()),
                FontSource::emoji(),
                FontSource::families("Mona Sans, Garamond"),
                FontSource::fantasy(),
                FontSource::ui_monospace(),
                FontSource::family("Fira Mono"),
            ]
        );
    }

    #[test]
    fn empty_font_source_list_is_empty_and_resolves_to_empty_family_list() {
        let list = FontSource::List(Vec::new());
        assert!(list.flatten().is_empty());
        assert_eq!(
            list.resolve_font_family(&Assets::<Font>::default()),
            Ok(FontFamily::List(Cow::Owned(Vec::new())))
        );
    }

    #[test]
    fn singleton_font_source_list_resolves_handle_to_single_family() {
        let mut dummy_font = Font::from_bytes(Vec::new());
        dummy_font.alias = "Dummy Font".to_string();
        let mut fonts = Assets::<Font>::default();
        let dummy_font_handle = fonts.add(dummy_font.clone());
        let source = FontSource::list([FontSource::from(dummy_font_handle)]);

        assert_eq!(
            source.resolve_font_family(&fonts),
            Ok(FontFamily::Single(parley::FontFamilyName::Named(
                Cow::Borrowed("Dummy Font")
            )))
        );
    }
}