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|
use super::*;
/// A node that stacks and aligns its children.
///
/// # Alignment
/// Individual layouts can be aligned at `Start`, `Center` or `End` along both
/// axes. These alignments are with processed with respect to the size of the
/// finished layout and not the total usable size. This means that a later
/// layout can have influence on the position of an earlier one. Consider the
/// following example.
/// ```typst
/// [align: right][A word.]
/// [align: left][A sentence with a couple more words.]
/// ```
/// The resulting layout looks like this:
/// ```text
/// |--------------------------------------|
/// | A word. |
/// | |
/// | A sentence with a couple more words. |
/// |--------------------------------------|
/// ```
/// The position of the first aligned box thus depends on the length of the
/// sentence in the second box.
#[derive(Debug, Clone, PartialEq)]
pub struct Stack {
pub dirs: Gen<Dir>,
pub children: Vec<LayoutNode>,
pub aligns: Gen<Align>,
pub expand: Spec<bool>,
}
#[async_trait(?Send)]
impl Layout for Stack {
async fn layout(
&self,
ctx: &mut LayoutContext,
constraints: LayoutConstraints,
) -> Vec<Layouted> {
let mut items = vec![];
let size = constraints.spaces[0].size;
let mut space = StackSpace::new(self.dirs, self.expand, size);
let mut i = 0;
for child in &self.children {
let child_constraints = LayoutConstraints {
spaces: {
let mut remaining = vec![LayoutSpace {
base: space.full_size,
size: space.usable,
}];
let next = (i + 1).min(constraints.spaces.len() - 1);
remaining.extend(&constraints.spaces[next ..]);
remaining
},
repeat: constraints.repeat,
};
for item in child.layout(ctx, child_constraints).await {
match item {
Layouted::Spacing(spacing) => space.push_spacing(spacing),
Layouted::Box(mut boxed, aligns) => {
let mut last = false;
while let Err(back) = space.push_box(boxed, aligns) {
boxed = back;
if last {
break;
}
items.push(Layouted::Box(space.finish(), self.aligns));
if i + 1 < constraints.spaces.len() {
i += 1;
} else {
last = true;
}
let size = constraints.spaces[i].size;
space = StackSpace::new(self.dirs, self.expand, size);
}
}
}
}
}
items.push(Layouted::Box(space.finish(), self.aligns));
items
}
}
struct StackSpace {
dirs: Gen<Dir>,
expand: Spec<bool>,
boxes: Vec<(BoxLayout, Gen<Align>)>,
full_size: Size,
usable: Size,
used: Size,
ruler: Align,
}
impl StackSpace {
fn new(dirs: Gen<Dir>, expand: Spec<bool>, size: Size) -> Self {
Self {
dirs,
expand,
boxes: vec![],
full_size: size,
usable: size,
used: Size::ZERO,
ruler: Align::Start,
}
}
fn push_box(
&mut self,
boxed: BoxLayout,
aligns: Gen<Align>,
) -> Result<(), BoxLayout> {
let main = self.dirs.main.axis();
let cross = self.dirs.cross.axis();
if aligns.main < self.ruler || !self.usable.fits(boxed.size) {
return Err(boxed);
}
let size = boxed.size.switch(self.dirs);
*self.used.get_mut(cross) = self.used.get(cross).max(size.cross);
*self.used.get_mut(main) += size.main;
*self.usable.get_mut(main) -= size.main;
self.boxes.push((boxed, aligns));
self.ruler = aligns.main;
Ok(())
}
fn push_spacing(&mut self, spacing: Length) {
let main = self.dirs.main.axis();
let max = self.usable.get(main);
let trimmed = spacing.min(max);
*self.used.get_mut(main) += trimmed;
*self.usable.get_mut(main) -= trimmed;
let size = Gen::new(trimmed, Length::ZERO).switch(self.dirs);
self.boxes.push((BoxLayout::new(size.to_size()), Gen::default()));
}
fn finish(mut self) -> BoxLayout {
let dirs = self.dirs;
let main = dirs.main.axis();
if self.expand.horizontal {
self.used.width = self.full_size.width;
}
if self.expand.vertical {
self.used.height = self.full_size.height;
}
let mut sum = Length::ZERO;
let mut sums = Vec::with_capacity(self.boxes.len() + 1);
for (boxed, _) in &self.boxes {
sums.push(sum);
sum += boxed.size.get(main);
}
sums.push(sum);
let mut layout = BoxLayout::new(self.used);
let used = self.used.switch(dirs);
for (i, (boxed, aligns)) in self.boxes.into_iter().enumerate() {
let size = boxed.size.switch(dirs);
let before = sums[i];
let after = sum - sums[i + 1];
let main_len = used.main - size.main;
let main_range = if dirs.main.is_positive() {
before .. main_len - after
} else {
main_len - before .. after
};
let cross_len = used.cross - size.cross;
let cross_range = if dirs.cross.is_positive() {
Length::ZERO .. cross_len
} else {
cross_len .. Length::ZERO
};
let main = aligns.main.apply(main_range);
let cross = aligns.cross.apply(cross_range);
let pos = Gen::new(main, cross).switch(dirs).to_point();
layout.push_layout(pos, boxed);
}
layout
}
}
impl From<Stack> for LayoutNode {
fn from(stack: Stack) -> Self {
Self::dynamic(stack)
}
}
|
