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use std::fmt::{self, Debug, Formatter};
use std::hash::{Hash, Hasher};
use std::rc::Rc;
use super::*;
use crate::geom::{Length, Size};
/// Page-level nodes directly produce frames representing pages.
///
/// Such nodes create their own regions instead of being supplied with them from
/// some parent.
pub trait PageLevel: Debug {
/// Layout the node, producing one frame per page.
fn layout(&self, ctx: &mut LayoutContext) -> Vec<Rc<Frame>>;
}
/// Layouts its children onto one or multiple pages.
#[derive(Debug)]
pub struct PageNode {
/// The size of the page.
pub size: Size,
/// The node that produces the actual pages.
pub child: BlockNode,
}
impl PageLevel for PageNode {
fn layout(&self, ctx: &mut LayoutContext) -> Vec<Rc<Frame>> {
// When one of the lengths is infinite the page fits its content along
// that axis.
let expand = self.size.to_spec().map(Length::is_finite);
let regions = Regions::repeat(self.size, self.size, expand);
self.child.layout(ctx, ®ions).into_iter().map(|c| c.item).collect()
}
}
impl<T> PageLevel for T
where
T: AsRef<[PageNode]> + Debug + ?Sized,
{
fn layout(&self, ctx: &mut LayoutContext) -> Vec<Rc<Frame>> {
self.as_ref().iter().flat_map(|node| node.layout(ctx)).collect()
}
}
/// Block-level nodes can be layouted into a sequence of regions.
///
/// They return one frame per used region alongside constraints that define
/// whether the result is reusable in other regions.
pub trait BlockLevel: Debug {
/// Layout the node into the given regions, producing constrained frames.
fn layout(
&self,
ctx: &mut LayoutContext,
regions: &Regions,
) -> Vec<Constrained<Rc<Frame>>>;
/// Convert to a packed block-level node.
fn pack(self) -> BlockNode
where
Self: Sized + Hash + 'static,
{
BlockNode {
#[cfg(feature = "layout-cache")]
hash: hash_node(&self),
node: Rc::new(self),
}
}
}
/// A packed [block-level](BlockLevel) layouting node with precomputed hash.
#[derive(Clone)]
pub struct BlockNode {
node: Rc<dyn BlockLevel>,
#[cfg(feature = "layout-cache")]
hash: u64,
}
impl BlockLevel for BlockNode {
fn layout(
&self,
ctx: &mut LayoutContext,
regions: &Regions,
) -> Vec<Constrained<Rc<Frame>>> {
#[cfg(not(feature = "layout-cache"))]
return self.node.layout(ctx, regions);
#[cfg(feature = "layout-cache")]
ctx.layouts.get(self.hash, regions).unwrap_or_else(|| {
ctx.level += 1;
let frames = self.node.layout(ctx, regions);
ctx.level -= 1;
let entry = FramesEntry::new(frames.clone(), ctx.level);
#[cfg(debug_assertions)]
if !entry.check(regions) {
eprintln!("node: {:#?}", self.node);
eprintln!("regions: {:#?}", regions);
eprintln!(
"constraints: {:#?}",
frames.iter().map(|c| c.cts).collect::<Vec<_>>()
);
panic!("constraints did not match regions they were created for");
}
ctx.layouts.insert(self.hash, entry);
frames
})
}
fn pack(self) -> BlockNode
where
Self: Sized + Hash + 'static,
{
self
}
}
impl Hash for BlockNode {
fn hash<H: Hasher>(&self, _state: &mut H) {
#[cfg(feature = "layout-cache")]
_state.write_u64(self.hash);
#[cfg(not(feature = "layout-cache"))]
unimplemented!()
}
}
impl Debug for BlockNode {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
self.node.fmt(f)
}
}
/// Inline-level nodes are layouted as part of paragraph layout.
///
/// They only know the width and not the height of the paragraph's region and
/// return only a single frame.
pub trait InlineLevel: Debug {
/// Layout the node into a frame.
fn layout(&self, ctx: &mut LayoutContext, space: Length, base: Size) -> Frame;
/// Convert to a packed inline-level node.
fn pack(self) -> InlineNode
where
Self: Sized + Hash + 'static,
{
InlineNode {
#[cfg(feature = "layout-cache")]
hash: hash_node(&self),
node: Rc::new(self),
}
}
}
/// A packed [inline-level](InlineLevel) layouting node with precomputed hash.
#[derive(Clone)]
pub struct InlineNode {
node: Rc<dyn InlineLevel>,
#[cfg(feature = "layout-cache")]
hash: u64,
}
impl InlineLevel for InlineNode {
fn layout(&self, ctx: &mut LayoutContext, space: Length, base: Size) -> Frame {
self.node.layout(ctx, space, base)
}
fn pack(self) -> InlineNode
where
Self: Sized + Hash + 'static,
{
self
}
}
impl Hash for InlineNode {
fn hash<H: Hasher>(&self, _state: &mut H) {
#[cfg(feature = "layout-cache")]
_state.write_u64(self.hash);
#[cfg(not(feature = "layout-cache"))]
unimplemented!()
}
}
impl Debug for InlineNode {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
self.node.fmt(f)
}
}
/// Hash a node alongside its type id.
#[cfg(feature = "layout-cache")]
fn hash_node(node: &(impl Hash + 'static)) -> u64 {
use std::any::Any;
let mut state = fxhash::FxHasher64::default();
node.type_id().hash(&mut state);
node.hash(&mut state);
state.finish()
}
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