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//! Element interaction.
use typst::model::{Behave, Behaviour, Content, StyleChain, StyleVec, StyleVecBuilder};
/// A wrapper around a [`StyleVecBuilder`] that allows elements to interact.
#[derive(Debug)]
pub struct BehavedBuilder<'a> {
/// The internal builder.
builder: StyleVecBuilder<'a, Content>,
/// Staged weak and ignorant elements that we can't yet commit to the
/// builder. The option is `Some(_)` for weak elements and `None` for
/// ignorant elements.
staged: Vec<(Content, Behaviour, StyleChain<'a>)>,
/// What the last non-ignorant item was.
last: Behaviour,
}
impl<'a> BehavedBuilder<'a> {
/// Create a new style-vec builder.
pub fn new() -> Self {
Self {
builder: StyleVecBuilder::new(),
staged: vec![],
last: Behaviour::Destructive,
}
}
/// Whether the builder is totally empty.
pub fn is_empty(&self) -> bool {
self.builder.is_empty() && self.staged.is_empty()
}
/// Whether the builder is empty except for some weak elements that will
/// probably collapse.
pub fn is_basically_empty(&self) -> bool {
self.builder.is_empty()
&& self
.staged
.iter()
.all(|(_, behaviour, _)| matches!(behaviour, Behaviour::Weak(_)))
}
/// Push an item into the sequence.
pub fn push(&mut self, elem: Content, styles: StyleChain<'a>) {
let interaction = elem
.with::<dyn Behave>()
.map_or(Behaviour::Supportive, Behave::behaviour);
match interaction {
Behaviour::Weak(level) => {
if matches!(self.last, Behaviour::Weak(_)) {
let item = elem.with::<dyn Behave>().unwrap();
let i = self.staged.iter().position(|prev| {
let Behaviour::Weak(prev_level) = prev.1 else { return false };
level < prev_level
|| (level == prev_level && item.larger(&prev.0))
});
let Some(i) = i else { return };
self.staged.remove(i);
}
if self.last != Behaviour::Destructive {
self.staged.push((elem, interaction, styles));
self.last = interaction;
}
}
Behaviour::Supportive => {
self.flush(true);
self.builder.push(elem, styles);
self.last = interaction;
}
Behaviour::Destructive => {
self.flush(false);
self.builder.push(elem, styles);
self.last = interaction;
}
Behaviour::Ignorant => {
self.staged.push((elem, interaction, styles));
}
}
}
/// Iterate over the contained elements.
pub fn elems(&self) -> impl DoubleEndedIterator<Item = &Content> {
self.builder.elems().chain(self.staged.iter().map(|(item, ..)| item))
}
/// Return the finish style vec and the common prefix chain.
pub fn finish(mut self) -> (StyleVec<Content>, StyleChain<'a>) {
self.flush(false);
self.builder.finish()
}
/// Push the staged elements, filtering out weak elements if `supportive` is
/// false.
fn flush(&mut self, supportive: bool) {
for (item, interaction, styles) in self.staged.drain(..) {
if supportive || interaction == Behaviour::Ignorant {
self.builder.push(item, styles);
}
}
}
}
impl<'a> Default for BehavedBuilder<'a> {
fn default() -> Self {
Self::new()
}
}
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