Inline tui as helix-tui fork.

We only rely on some of the rendering primitives and implement our
Cursive-style compositor on top.

1 files changed, 534 insertions, 0 deletions

diff --git a/helix-tui/src/layout.rs b/helix-tui/src/layout.rs
new file mode 100644
index 00000000..5248f7bf
--- /dev/null
+++ b/helix-tui/src/layout.rs
@@ -0,0 +1,534 @@
+use std::cell::RefCell;
+use std::cmp::{max, min};
+use std::collections::HashMap;
+
+use cassowary::strength::{REQUIRED, WEAK};
+use cassowary::WeightedRelation::*;
+use cassowary::{Constraint as CassowaryConstraint, Expression, Solver, Variable};
+
+#[derive(Debug, Hash, Clone, Copy, PartialEq, Eq)]
+pub enum Corner {
+    TopLeft,
+    TopRight,
+    BottomRight,
+    BottomLeft,
+}
+
+#[derive(Debug, Hash, Clone, PartialEq, Eq)]
+pub enum Direction {
+    Horizontal,
+    Vertical,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum Constraint {
+    // TODO: enforce range 0 - 100
+    Percentage(u16),
+    Ratio(u32, u32),
+    Length(u16),
+    Max(u16),
+    Min(u16),
+}
+
+impl Constraint {
+    pub fn apply(&self, length: u16) -> u16 {
+        match *self {
+            Constraint::Percentage(p) => length * p / 100,
+            Constraint::Ratio(num, den) => {
+                let r = num * u32::from(length) / den;
+                r as u16
+            }
+            Constraint::Length(l) => length.min(l),
+            Constraint::Max(m) => length.min(m),
+            Constraint::Min(m) => length.max(m),
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Margin {
+    pub vertical: u16,
+    pub horizontal: u16,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum Alignment {
+    Left,
+    Center,
+    Right,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Layout {
+    direction: Direction,
+    margin: Margin,
+    constraints: Vec<Constraint>,
+}
+
+thread_local! {
+    static LAYOUT_CACHE: RefCell<HashMap<(Rect, Layout), Vec<Rect>>> = RefCell::new(HashMap::new());
+}
+
+impl Default for Layout {
+    fn default() -> Layout {
+        Layout {
+            direction: Direction::Vertical,
+            margin: Margin {
+                horizontal: 0,
+                vertical: 0,
+            },
+            constraints: Vec::new(),
+        }
+    }
+}
+
+impl Layout {
+    pub fn constraints<C>(mut self, constraints: C) -> Layout
+    where
+        C: Into<Vec<Constraint>>,
+    {
+        self.constraints = constraints.into();
+        self
+    }
+
+    pub fn margin(mut self, margin: u16) -> Layout {
+        self.margin = Margin {
+            horizontal: margin,
+            vertical: margin,
+        };
+        self
+    }
+
+    pub fn horizontal_margin(mut self, horizontal: u16) -> Layout {
+        self.margin.horizontal = horizontal;
+        self
+    }
+
+    pub fn vertical_margin(mut self, vertical: u16) -> Layout {
+        self.margin.vertical = vertical;
+        self
+    }
+
+    pub fn direction(mut self, direction: Direction) -> Layout {
+        self.direction = direction;
+        self
+    }
+
+    /// Wrapper function around the cassowary-rs solver to be able to split a given
+    /// area into smaller ones based on the preferred widths or heights and the direction.
+    ///
+    /// # Examples
+    /// ```
+    /// # use helix_tui::layout::{Rect, Constraint, Direction, Layout};
+    /// let chunks = Layout::default()
+    ///     .direction(Direction::Vertical)
+    ///     .constraints([Constraint::Length(5), Constraint::Min(0)].as_ref())
+    ///     .split(Rect {
+    ///         x: 2,
+    ///         y: 2,
+    ///         width: 10,
+    ///         height: 10,
+    ///     });
+    /// assert_eq!(
+    ///     chunks,
+    ///     vec![
+    ///         Rect {
+    ///             x: 2,
+    ///             y: 2,
+    ///             width: 10,
+    ///             height: 5
+    ///         },
+    ///         Rect {
+    ///             x: 2,
+    ///             y: 7,
+    ///             width: 10,
+    ///             height: 5
+    ///         }
+    ///     ]
+    /// );
+    ///
+    /// let chunks = Layout::default()
+    ///     .direction(Direction::Horizontal)
+    ///     .constraints([Constraint::Ratio(1, 3), Constraint::Ratio(2, 3)].as_ref())
+    ///     .split(Rect {
+    ///         x: 0,
+    ///         y: 0,
+    ///         width: 9,
+    ///         height: 2,
+    ///     });
+    /// assert_eq!(
+    ///     chunks,
+    ///     vec![
+    ///         Rect {
+    ///             x: 0,
+    ///             y: 0,
+    ///             width: 3,
+    ///             height: 2
+    ///         },
+    ///         Rect {
+    ///             x: 3,
+    ///             y: 0,
+    ///             width: 6,
+    ///             height: 2
+    ///         }
+    ///     ]
+    /// );
+    /// ```
+    pub fn split(&self, area: Rect) -> Vec<Rect> {
+        // TODO: Maybe use a fixed size cache ?
+        LAYOUT_CACHE.with(|c| {
+            c.borrow_mut()
+                .entry((area, self.clone()))
+                .or_insert_with(|| split(area, self))
+                .clone()
+        })
+    }
+}
+
+fn split(area: Rect, layout: &Layout) -> Vec<Rect> {
+    let mut solver = Solver::new();
+    let mut vars: HashMap<Variable, (usize, usize)> = HashMap::new();
+    let elements = layout
+        .constraints
+        .iter()
+        .map(|_| Element::new())
+        .collect::<Vec<Element>>();
+    let mut results = layout
+        .constraints
+        .iter()
+        .map(|_| Rect::default())
+        .collect::<Vec<Rect>>();
+
+    let dest_area = area.inner(&layout.margin);
+    for (i, e) in elements.iter().enumerate() {
+        vars.insert(e.x, (i, 0));
+        vars.insert(e.y, (i, 1));
+        vars.insert(e.width, (i, 2));
+        vars.insert(e.height, (i, 3));
+    }
+    let mut ccs: Vec<CassowaryConstraint> =
+        Vec::with_capacity(elements.len() * 4 + layout.constraints.len() * 6);
+    for elt in &elements {
+        ccs.push(elt.width | GE(REQUIRED) | 0f64);
+        ccs.push(elt.height | GE(REQUIRED) | 0f64);
+        ccs.push(elt.left() | GE(REQUIRED) | f64::from(dest_area.left()));
+        ccs.push(elt.top() | GE(REQUIRED) | f64::from(dest_area.top()));
+        ccs.push(elt.right() | LE(REQUIRED) | f64::from(dest_area.right()));
+        ccs.push(elt.bottom() | LE(REQUIRED) | f64::from(dest_area.bottom()));
+    }
+    if let Some(first) = elements.first() {
+        ccs.push(match layout.direction {
+            Direction::Horizontal => first.left() | EQ(REQUIRED) | f64::from(dest_area.left()),
+            Direction::Vertical => first.top() | EQ(REQUIRED) | f64::from(dest_area.top()),
+        });
+    }
+    if let Some(last) = elements.last() {
+        ccs.push(match layout.direction {
+            Direction::Horizontal => last.right() | EQ(REQUIRED) | f64::from(dest_area.right()),
+            Direction::Vertical => last.bottom() | EQ(REQUIRED) | f64::from(dest_area.bottom()),
+        });
+    }
+    match layout.direction {
+        Direction::Horizontal => {
+            for pair in elements.windows(2) {
+                ccs.push((pair[0].x + pair[0].width) | EQ(REQUIRED) | pair[1].x);
+            }
+            for (i, size) in layout.constraints.iter().enumerate() {
+                ccs.push(elements[i].y | EQ(REQUIRED) | f64::from(dest_area.y));
+                ccs.push(elements[i].height | EQ(REQUIRED) | f64::from(dest_area.height));
+                ccs.push(match *size {
+                    Constraint::Length(v) => elements[i].width | EQ(WEAK) | f64::from(v),
+                    Constraint::Percentage(v) => {
+                        elements[i].width | EQ(WEAK) | (f64::from(v * dest_area.width) / 100.0)
+                    }
+                    Constraint::Ratio(n, d) => {
+                        elements[i].width
+                            | EQ(WEAK)
+                            | (f64::from(dest_area.width) * f64::from(n) / f64::from(d))
+                    }
+                    Constraint::Min(v) => elements[i].width | GE(WEAK) | f64::from(v),
+                    Constraint::Max(v) => elements[i].width | LE(WEAK) | f64::from(v),
+                });
+            }
+        }
+        Direction::Vertical => {
+            for pair in elements.windows(2) {
+                ccs.push((pair[0].y + pair[0].height) | EQ(REQUIRED) | pair[1].y);
+            }
+            for (i, size) in layout.constraints.iter().enumerate() {
+                ccs.push(elements[i].x | EQ(REQUIRED) | f64::from(dest_area.x));
+                ccs.push(elements[i].width | EQ(REQUIRED) | f64::from(dest_area.width));
+                ccs.push(match *size {
+                    Constraint::Length(v) => elements[i].height | EQ(WEAK) | f64::from(v),
+                    Constraint::Percentage(v) => {
+                        elements[i].height | EQ(WEAK) | (f64::from(v * dest_area.height) / 100.0)
+                    }
+                    Constraint::Ratio(n, d) => {
+                        elements[i].height
+                            | EQ(WEAK)
+                            | (f64::from(dest_area.height) * f64::from(n) / f64::from(d))
+                    }
+                    Constraint::Min(v) => elements[i].height | GE(WEAK) | f64::from(v),
+                    Constraint::Max(v) => elements[i].height | LE(WEAK) | f64::from(v),
+                });
+            }
+        }
+    }
+    solver.add_constraints(&ccs).unwrap();
+    for &(var, value) in solver.fetch_changes() {
+        let (index, attr) = vars[&var];
+        let value = if value.is_sign_negative() {
+            0
+        } else {
+            value as u16
+        };
+        match attr {
+            0 => {
+                results[index].x = value;
+            }
+            1 => {
+                results[index].y = value;
+            }
+            2 => {
+                results[index].width = value;
+            }
+            3 => {
+                results[index].height = value;
+            }
+            _ => {}
+        }
+    }
+
+    // Fix imprecision by extending the last item a bit if necessary
+    if let Some(last) = results.last_mut() {
+        match layout.direction {
+            Direction::Vertical => {
+                last.height = dest_area.bottom() - last.y;
+            }
+            Direction::Horizontal => {
+                last.width = dest_area.right() - last.x;
+            }
+        }
+    }
+    results
+}
+
+/// A container used by the solver inside split
+struct Element {
+    x: Variable,
+    y: Variable,
+    width: Variable,
+    height: Variable,
+}
+
+impl Element {
+    fn new() -> Element {
+        Element {
+            x: Variable::new(),
+            y: Variable::new(),
+            width: Variable::new(),
+            height: Variable::new(),
+        }
+    }
+
+    fn left(&self) -> Variable {
+        self.x
+    }
+
+    fn top(&self) -> Variable {
+        self.y
+    }
+
+    fn right(&self) -> Expression {
+        self.x + self.width
+    }
+
+    fn bottom(&self) -> Expression {
+        self.y + self.height
+    }
+}
+
+/// A simple rectangle used in the computation of the layout and to give widgets an hint about the
+/// area they are supposed to render to.
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
+pub struct Rect {
+    pub x: u16,
+    pub y: u16,
+    pub width: u16,
+    pub height: u16,
+}
+
+impl Default for Rect {
+    fn default() -> Rect {
+        Rect {
+            x: 0,
+            y: 0,
+            width: 0,
+            height: 0,
+        }
+    }
+}
+
+impl Rect {
+    /// Creates a new rect, with width and height limited to keep the area under max u16.
+    /// If clipped, aspect ratio will be preserved.
+    pub fn new(x: u16, y: u16, width: u16, height: u16) -> Rect {
+        let max_area = u16::max_value();
+        let (clipped_width, clipped_height) =
+            if u32::from(width) * u32::from(height) > u32::from(max_area) {
+                let aspect_ratio = f64::from(width) / f64::from(height);
+                let max_area_f = f64::from(max_area);
+                let height_f = (max_area_f / aspect_ratio).sqrt();
+                let width_f = height_f * aspect_ratio;
+                (width_f as u16, height_f as u16)
+            } else {
+                (width, height)
+            };
+        Rect {
+            x,
+            y,
+            width: clipped_width,
+            height: clipped_height,
+        }
+    }
+
+    pub fn area(self) -> u16 {
+        self.width * self.height
+    }
+
+    pub fn left(self) -> u16 {
+        self.x
+    }
+
+    pub fn right(self) -> u16 {
+        self.x.saturating_add(self.width)
+    }
+
+    pub fn top(self) -> u16 {
+        self.y
+    }
+
+    pub fn bottom(self) -> u16 {
+        self.y.saturating_add(self.height)
+    }
+
+    pub fn inner(self, margin: &Margin) -> Rect {
+        if self.width < 2 * margin.horizontal || self.height < 2 * margin.vertical {
+            Rect::default()
+        } else {
+            Rect {
+                x: self.x + margin.horizontal,
+                y: self.y + margin.vertical,
+                width: self.width - 2 * margin.horizontal,
+                height: self.height - 2 * margin.vertical,
+            }
+        }
+    }
+
+    pub fn union(self, other: Rect) -> Rect {
+        let x1 = min(self.x, other.x);
+        let y1 = min(self.y, other.y);
+        let x2 = max(self.x + self.width, other.x + other.width);
+        let y2 = max(self.y + self.height, other.y + other.height);
+        Rect {
+            x: x1,
+            y: y1,
+            width: x2 - x1,
+            height: y2 - y1,
+        }
+    }
+
+    pub fn intersection(self, other: Rect) -> Rect {
+        let x1 = max(self.x, other.x);
+        let y1 = max(self.y, other.y);
+        let x2 = min(self.x + self.width, other.x + other.width);
+        let y2 = min(self.y + self.height, other.y + other.height);
+        Rect {
+            x: x1,
+            y: y1,
+            width: x2 - x1,
+            height: y2 - y1,
+        }
+    }
+
+    pub fn intersects(self, other: Rect) -> bool {
+        self.x < other.x + other.width
+            && self.x + self.width > other.x
+            && self.y < other.y + other.height
+            && self.y + self.height > other.y
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_vertical_split_by_height() {
+        let target = Rect {
+            x: 2,
+            y: 2,
+            width: 10,
+            height: 10,
+        };
+
+        let chunks = Layout::default()
+            .direction(Direction::Vertical)
+            .constraints(
+                [
+                    Constraint::Percentage(10),
+                    Constraint::Max(5),
+                    Constraint::Min(1),
+                ]
+                .as_ref(),
+            )
+            .split(target);
+
+        assert_eq!(target.height, chunks.iter().map(|r| r.height).sum::<u16>());
+        chunks.windows(2).for_each(|w| assert!(w[0].y <= w[1].y));
+    }
+
+    #[test]
+    fn test_rect_size_truncation() {
+        for width in 256u16..300u16 {
+            for height in 256u16..300u16 {
+                let rect = Rect::new(0, 0, width, height);
+                rect.area(); // Should not panic.
+                assert!(rect.width < width || rect.height < height);
+                // The target dimensions are rounded down so the math will not be too precise
+                // but let's make sure the ratios don't diverge crazily.
+                assert!(
+                    (f64::from(rect.width) / f64::from(rect.height)
+                        - f64::from(width) / f64::from(height))
+                    .abs()
+                        < 1.0
+                )
+            }
+        }
+
+        // One dimension below 255, one above. Area above max u16.
+        let width = 900;
+        let height = 100;
+        let rect = Rect::new(0, 0, width, height);
+        assert_ne!(rect.width, 900);
+        assert_ne!(rect.height, 100);
+        assert!(rect.width < width || rect.height < height);
+    }
+
+    #[test]
+    fn test_rect_size_preservation() {
+        for width in 0..256u16 {
+            for height in 0..256u16 {
+                let rect = Rect::new(0, 0, width, height);
+                rect.area(); // Should not panic.
+                assert_eq!(rect.width, width);
+                assert_eq!(rect.height, height);
+            }
+        }
+
+        // One dimension below 255, one above. Area below max u16.
+        let rect = Rect::new(0, 0, 300, 100);
+        assert_eq!(rect.width, 300);
+        assert_eq!(rect.height, 100);
+    }
+}