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https://github.com/typst/typst
synced 2025-05-19 03:25:27 +08:00
Refactor stack layout again 🧣
This commit is contained in:
Laurenz
parent
d3bc4ec073
commit
607f4395f9
@ -1,201 +1,34 @@
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use super::*;
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/// A node that stacks and aligns its children.
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///
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/// # Alignment
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/// Individual layouts can be aligned at `Start`, `Center` or `End` along both
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/// axes. These alignments are with processed with respect to the size of the
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/// finished layout and not the total usable size. This means that a later
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/// layout can have influence on the position of an earlier one. Consider the
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/// following example.
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/// ```typst
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/// [align: right][A word.]
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/// [align: left][A sentence with a couple more words.]
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/// ```
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/// The resulting layout looks like this:
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/// ```text
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/// |--------------------------------------|
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/// | A word. |
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/// | |
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/// | A sentence with a couple more words. |
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/// |--------------------------------------|
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/// ```
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/// The position of the first aligned box thus depends on the length of the
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/// sentence in the second box.
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#[derive(Debug, Clone, PartialEq)]
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pub struct Stack {
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/// The `main` and `cross` directions of this stack.
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///
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/// The children are stacked along the `main` direction. The `cross`
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/// direction is required for aligning the children.
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pub dirs: Gen<Dir>,
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pub children: Vec<LayoutNode>,
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/// How to align _this_ stack in _its_ parent.
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pub aligns: Gen<Align>,
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pub expand: Spec<bool>,
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/// Whether to expand the axes to fill the area or to fit the content.
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pub expansion: Gen<Expansion>,
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/// The nodes to be stacked.
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pub children: Vec<LayoutNode>,
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}
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#[async_trait(?Send)]
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impl Layout for Stack {
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async fn layout(
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&self,
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ctx: &mut LayoutContext,
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constraints: LayoutConstraints,
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) -> Vec<Layouted> {
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let mut items = vec![];
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let size = constraints.spaces[0].size;
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let mut space = StackSpace::new(self.dirs, self.expand, size);
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let mut i = 0;
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async fn layout(&self, ctx: &mut LayoutContext, areas: &Areas) -> Vec<Layouted> {
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let mut layouter = StackLayouter::new(self, areas.clone());
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for child in &self.children {
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let child_constraints = LayoutConstraints {
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spaces: {
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let mut remaining = vec![LayoutSpace {
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base: space.full_size,
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size: space.usable,
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}];
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let next = (i + 1).min(constraints.spaces.len() - 1);
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remaining.extend(&constraints.spaces[next ..]);
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remaining
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},
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repeat: constraints.repeat,
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};
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for item in child.layout(ctx, child_constraints).await {
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match item {
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Layouted::Spacing(spacing) => space.push_spacing(spacing),
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Layouted::Box(mut boxed, aligns) => {
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let mut last = false;
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while let Err(back) = space.push_box(boxed, aligns) {
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boxed = back;
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if last {
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break;
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}
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items.push(Layouted::Box(space.finish(), self.aligns));
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if i + 1 < constraints.spaces.len() {
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i += 1;
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} else {
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last = true;
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}
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let size = constraints.spaces[i].size;
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space = StackSpace::new(self.dirs, self.expand, size);
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}
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}
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for layouted in child.layout(ctx, &layouter.areas).await {
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match layouted {
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Layouted::Spacing(spacing) => layouter.spacing(spacing),
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Layouted::Boxed(boxed, aligns) => layouter.boxed(boxed, aligns),
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}
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}
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}
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items.push(Layouted::Box(space.finish(), self.aligns));
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items
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}
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}
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struct StackSpace {
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dirs: Gen<Dir>,
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expand: Spec<bool>,
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boxes: Vec<(BoxLayout, Gen<Align>)>,
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full_size: Size,
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usable: Size,
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used: Size,
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ruler: Align,
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}
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impl StackSpace {
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fn new(dirs: Gen<Dir>, expand: Spec<bool>, size: Size) -> Self {
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Self {
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dirs,
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expand,
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boxes: vec![],
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full_size: size,
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usable: size,
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used: Size::ZERO,
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ruler: Align::Start,
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}
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}
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fn push_box(
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&mut self,
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boxed: BoxLayout,
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aligns: Gen<Align>,
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) -> Result<(), BoxLayout> {
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let main = self.dirs.main.axis();
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let cross = self.dirs.cross.axis();
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if aligns.main < self.ruler || !self.usable.fits(boxed.size) {
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return Err(boxed);
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}
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let size = boxed.size.switch(self.dirs);
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*self.used.get_mut(cross) = self.used.get(cross).max(size.cross);
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*self.used.get_mut(main) += size.main;
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*self.usable.get_mut(main) -= size.main;
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self.boxes.push((boxed, aligns));
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self.ruler = aligns.main;
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Ok(())
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}
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fn push_spacing(&mut self, spacing: Length) {
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let main = self.dirs.main.axis();
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let max = self.usable.get(main);
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let trimmed = spacing.min(max);
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*self.used.get_mut(main) += trimmed;
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*self.usable.get_mut(main) -= trimmed;
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let size = Gen::new(trimmed, Length::ZERO).switch(self.dirs);
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self.boxes.push((BoxLayout::new(size.to_size()), Gen::default()));
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}
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fn finish(mut self) -> BoxLayout {
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let dirs = self.dirs;
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let main = dirs.main.axis();
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if self.expand.horizontal {
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self.used.width = self.full_size.width;
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}
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if self.expand.vertical {
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self.used.height = self.full_size.height;
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}
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let mut sum = Length::ZERO;
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let mut sums = Vec::with_capacity(self.boxes.len() + 1);
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for (boxed, _) in &self.boxes {
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sums.push(sum);
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sum += boxed.size.get(main);
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}
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sums.push(sum);
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let mut layout = BoxLayout::new(self.used);
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let used = self.used.switch(dirs);
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for (i, (boxed, aligns)) in self.boxes.into_iter().enumerate() {
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let size = boxed.size.switch(dirs);
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let before = sums[i];
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let after = sum - sums[i + 1];
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let main_len = used.main - size.main;
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let main_range = if dirs.main.is_positive() {
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before .. main_len - after
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} else {
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main_len - before .. after
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};
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let cross_len = used.cross - size.cross;
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let cross_range = if dirs.cross.is_positive() {
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Length::ZERO .. cross_len
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} else {
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cross_len .. Length::ZERO
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};
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let main = aligns.main.apply(main_range);
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let cross = aligns.cross.apply(cross_range);
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let pos = Gen::new(main, cross).switch(dirs).to_point();
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layout.push_layout(pos, boxed);
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}
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layout
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layouter.finish()
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}
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}
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@ -204,3 +37,113 @@ impl From<Stack> for LayoutNode {
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Self::dynamic(stack)
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}
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}
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struct StackLayouter<'a> {
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stack: &'a Stack,
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main: SpecAxis,
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dirs: Gen<Dir>,
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areas: Areas,
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layouted: Vec<Layouted>,
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boxes: Vec<(Length, BoxLayout, Gen<Align>)>,
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used: Gen<Length>,
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ruler: Align,
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}
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impl<'a> StackLayouter<'a> {
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fn new(stack: &'a Stack, areas: Areas) -> Self {
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Self {
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stack,
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main: stack.dirs.main.axis(),
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dirs: stack.dirs,
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areas,
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layouted: vec![],
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boxes: vec![],
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used: Gen::ZERO,
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ruler: Align::Start,
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}
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}
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fn spacing(&mut self, amount: Length) {
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let main_rest = self.areas.current.rem.get_mut(self.main);
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let capped = amount.min(*main_rest);
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*main_rest -= capped;
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self.used.main += capped;
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}
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fn boxed(&mut self, layout: BoxLayout, aligns: Gen<Align>) {
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if self.ruler > aligns.main {
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self.finish_area();
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}
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while !self.areas.current.rem.fits(layout.size) {
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if self.areas.in_full_last() {
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// TODO: Diagnose once the necessary spans exist.
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let _ = warning!("cannot fit box into any area");
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break;
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} else {
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self.finish_area();
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}
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}
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let size = layout.size.switch(self.dirs);
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self.boxes.push((self.used.main, layout, aligns));
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*self.areas.current.rem.get_mut(self.main) -= size.main;
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self.used.main += size.main;
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self.used.cross = self.used.cross.max(size.cross);
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self.ruler = aligns.main;
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}
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fn finish_area(&mut self) {
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let size = {
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let full = self.areas.current.full.switch(self.dirs);
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Gen::new(
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match self.stack.expansion.main {
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Expansion::Fill => full.main,
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Expansion::Fit => self.used.main.min(full.main),
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},
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match self.stack.expansion.cross {
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Expansion::Fill => full.cross,
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Expansion::Fit => self.used.cross.min(full.cross),
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},
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)
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};
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let mut output = BoxLayout::new(size.switch(self.dirs).to_size());
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for (before, layout, aligns) in std::mem::take(&mut self.boxes) {
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let child_size = layout.size.switch(self.dirs);
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// Align along the main axis.
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let main = aligns.main.apply(if self.dirs.main.is_positive() {
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let after_with_self = self.used.main - before;
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before .. size.main - after_with_self
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} else {
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let before_with_self = before + child_size.main;
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let after = self.used.main - (before + child_size.main);
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size.main - before_with_self .. after
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});
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// Align along the cross axis.
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let cross = aligns.cross.apply(if self.dirs.cross.is_positive() {
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Length::ZERO .. size.cross - child_size.cross
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} else {
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size.cross - child_size.cross .. Length::ZERO
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});
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let pos = Gen::new(main, cross).switch(self.dirs).to_point();
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output.push_layout(pos, layout);
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}
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self.layouted.push(Layouted::Boxed(output, self.stack.aligns));
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self.areas.next();
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self.used = Gen::ZERO;
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self.ruler = Align::Start;
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}
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fn finish(mut self) -> Vec<Layouted> {
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self.finish_area();
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self.layouted
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}
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}
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