helix/helix-tui/src/style.rs

//! `style` contains the primitives used to control how your user interface will look.

use bitflags::bitflags;

#[derive(Debug, Clone, Copy, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum Color {
    Reset,
    Black,
    Red,
    Green,
    Yellow,
    Blue,
    Magenta,
    Cyan,
    Gray,
    DarkGray,
    LightRed,
    LightGreen,
    LightYellow,
    LightBlue,
    LightMagenta,
    LightCyan,
    White,
    Rgb(u8, u8, u8),
    Indexed(u8),
}

bitflags! {
    /// Modifier changes the way a piece of text is displayed.
    ///
    /// They are bitflags so they can easily be composed.
    ///
    /// ## Examples
    ///
    /// ```rust
    /// # use helix_tui::style::Modifier;
    ///
    /// let m = Modifier::BOLD | Modifier::ITALIC;
    /// ```
    #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
    pub struct Modifier: u16 {
        const BOLD              = 0b0000_0000_0001;
        const DIM               = 0b0000_0000_0010;
        const ITALIC            = 0b0000_0000_0100;
        const UNDERLINED        = 0b0000_0000_1000;
        const SLOW_BLINK        = 0b0000_0001_0000;
        const RAPID_BLINK       = 0b0000_0010_0000;
        const REVERSED          = 0b0000_0100_0000;
        const HIDDEN            = 0b0000_1000_0000;
        const CROSSED_OUT       = 0b0001_0000_0000;
    }
}

/// Style let you control the main characteristics of the displayed elements.
///
/// ```rust
/// # use helix_tui::style::{Color, Modifier, Style};
/// Style::default()
///     .fg(Color::Black)
///     .bg(Color::Green)
///     .add_modifier(Modifier::ITALIC | Modifier::BOLD);
/// ```
///
/// It represents an incremental change. If you apply the styles S1, S2, S3 to a cell of the
/// terminal buffer, the style of this cell will be the result of the merge of S1, S2 and S3, not
/// just S3.
///
/// ```rust
/// # use helix_tui::style::{Color, Modifier, Style};
/// # use helix_tui::buffer::Buffer;
/// # use helix_tui::layout::Rect;
/// let styles = [
///     Style::default().fg(Color::Blue).add_modifier(Modifier::BOLD | Modifier::ITALIC),
///     Style::default().bg(Color::Red),
///     Style::default().fg(Color::Yellow).remove_modifier(Modifier::ITALIC),
/// ];
/// let mut buffer = Buffer::empty(Rect::new(0, 0, 1, 1));
/// for style in &styles {
///   buffer.get_mut(0, 0).set_style(*style);
/// }
/// assert_eq!(
///     Style {
///         fg: Some(Color::Yellow),
///         bg: Some(Color::Red),
///         add_modifier: Modifier::BOLD,
///         sub_modifier: Modifier::empty(),
///     },
///     buffer.get(0, 0).style(),
/// );
/// ```
///
/// The default implementation returns a `Style` that does not modify anything. If you wish to
/// reset all properties until that point use [`Style::reset`].
///
/// ```
/// # use helix_tui::style::{Color, Modifier, Style};
/// # use helix_tui::buffer::Buffer;
/// # use helix_tui::layout::Rect;
/// let styles = [
///     Style::default().fg(Color::Blue).add_modifier(Modifier::BOLD | Modifier::ITALIC),
///     Style::reset().fg(Color::Yellow),
/// ];
/// let mut buffer = Buffer::empty(Rect::new(0, 0, 1, 1));
/// for style in &styles {
///   buffer.get_mut(0, 0).set_style(*style);
/// }
/// assert_eq!(
///     Style {
///         fg: Some(Color::Yellow),
///         bg: Some(Color::Reset),
///         add_modifier: Modifier::empty(),
///         sub_modifier: Modifier::empty(),
///     },
///     buffer.get(0, 0).style(),
/// );
/// ```
#[derive(Debug, Clone, Copy, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Style {
    pub fg: Option<Color>,
    pub bg: Option<Color>,
    pub add_modifier: Modifier,
    pub sub_modifier: Modifier,
}

impl Default for Style {
    fn default() -> Style {
        Style {
            fg: None,
            bg: None,
            add_modifier: Modifier::empty(),
            sub_modifier: Modifier::empty(),
        }
    }
}

impl Style {
    /// Returns a `Style` resetting all properties.
    pub fn reset() -> Style {
        Style {
            fg: Some(Color::Reset),
            bg: Some(Color::Reset),
            add_modifier: Modifier::empty(),
            sub_modifier: Modifier::all(),
        }
    }

    /// Changes the foreground color.
    ///
    /// ## Examples
    ///
    /// ```rust
    /// # use helix_tui::style::{Color, Style};
    /// let style = Style::default().fg(Color::Blue);
    /// let diff = Style::default().fg(Color::Red);
    /// assert_eq!(style.patch(diff), Style::default().fg(Color::Red));
    /// ```
    pub fn fg(mut self, color: Color) -> Style {
        self.fg = Some(color);
        self
    }

    /// Changes the background color.
    ///
    /// ## Examples
    ///
    /// ```rust
    /// # use helix_tui::style::{Color, Style};
    /// let style = Style::default().bg(Color::Blue);
    /// let diff = Style::default().bg(Color::Red);
    /// assert_eq!(style.patch(diff), Style::default().bg(Color::Red));
    /// ```
    pub fn bg(mut self, color: Color) -> Style {
        self.bg = Some(color);
        self
    }

    /// Changes the text emphasis.
    ///
    /// When applied, it adds the given modifier to the `Style` modifiers.
    ///
    /// ## Examples
    ///
    /// ```rust
    /// # use helix_tui::style::{Color, Modifier, Style};
    /// let style = Style::default().add_modifier(Modifier::BOLD);
    /// let diff = Style::default().add_modifier(Modifier::ITALIC);
    /// let patched = style.patch(diff);
    /// assert_eq!(patched.add_modifier, Modifier::BOLD | Modifier::ITALIC);
    /// assert_eq!(patched.sub_modifier, Modifier::empty());
    /// ```
    pub fn add_modifier(mut self, modifier: Modifier) -> Style {
        self.sub_modifier.remove(modifier);
        self.add_modifier.insert(modifier);
        self
    }

    /// Changes the text emphasis.
    ///
    /// When applied, it removes the given modifier from the `Style` modifiers.
    ///
    /// ## Examples
    ///
    /// ```rust
    /// # use helix_tui::style::{Color, Modifier, Style};
    /// let style = Style::default().add_modifier(Modifier::BOLD | Modifier::ITALIC);
    /// let diff = Style::default().remove_modifier(Modifier::ITALIC);
    /// let patched = style.patch(diff);
    /// assert_eq!(patched.add_modifier, Modifier::BOLD);
    /// assert_eq!(patched.sub_modifier, Modifier::ITALIC);
    /// ```
    pub fn remove_modifier(mut self, modifier: Modifier) -> Style {
        self.add_modifier.remove(modifier);
        self.sub_modifier.insert(modifier);
        self
    }

    /// Results in a combined style that is equivalent to applying the two individual styles to
    /// a style one after the other.
    ///
    /// ## Examples
    /// ```
    /// # use helix_tui::style::{Color, Modifier, Style};
    /// let style_1 = Style::default().fg(Color::Yellow);
    /// let style_2 = Style::default().bg(Color::Red);
    /// let combined = style_1.patch(style_2);
    /// assert_eq!(
    ///     Style::default().patch(style_1).patch(style_2),
    ///     Style::default().patch(combined));
    /// ```
    pub fn patch(mut self, other: Style) -> Style {
        self.fg = other.fg.or(self.fg);
        self.bg = other.bg.or(self.bg);

        self.add_modifier.remove(other.sub_modifier);
        self.add_modifier.insert(other.add_modifier);
        self.sub_modifier.remove(other.add_modifier);
        self.sub_modifier.insert(other.sub_modifier);

        self
    }
}

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

    fn styles() -> Vec<Style> {
        vec![
            Style::default(),
            Style::default().fg(Color::Yellow),
            Style::default().bg(Color::Yellow),
            Style::default().add_modifier(Modifier::BOLD),
            Style::default().remove_modifier(Modifier::BOLD),
            Style::default().add_modifier(Modifier::ITALIC),
            Style::default().remove_modifier(Modifier::ITALIC),
            Style::default().add_modifier(Modifier::ITALIC | Modifier::BOLD),
            Style::default().remove_modifier(Modifier::ITALIC | Modifier::BOLD),
        ]
    }

    #[test]
    fn combined_patch_gives_same_result_as_individual_patch() {
        let styles = styles();
        for &a in &styles {
            for &b in &styles {
                for &c in &styles {
                    for &d in &styles {
                        let combined = a.patch(b.patch(c.patch(d)));

                        assert_eq!(
                            Style::default().patch(a).patch(b).patch(c).patch(d),
                            Style::default().patch(combined)
                        );
                    }
                }
            }
        }
    }
}