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Diffstat (limited to 'helix-tui/src/layout.rs')
| -rw-r--r-- | helix-tui/src/layout.rs | 534 |
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); + } +} |