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|
use std::fmt::{self, Debug, Formatter};
use super::*;
/// A node that stacks its children.
#[derive(Debug)]
#[cfg_attr(feature = "layout-cache", derive(Hash))]
pub struct StackNode {
/// The stacking direction.
pub dir: Dir,
/// The nodes to be stacked.
pub children: Vec<StackChild>,
}
/// A child of a stack node.
#[cfg_attr(feature = "layout-cache", derive(Hash))]
pub enum StackChild {
/// Spacing between other nodes.
Spacing(Linear),
/// Any block node and how to align it in the stack.
Any(BlockNode, Align),
}
impl BlockLevel for StackNode {
fn layout(
&self,
ctx: &mut LayoutContext,
regions: &Regions,
) -> Vec<Constrained<Rc<Frame>>> {
StackLayouter::new(self, regions.clone()).layout(ctx)
}
}
impl From<StackNode> for BlockNode {
fn from(node: StackNode) -> Self {
Self::new(node)
}
}
impl Debug for StackChild {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
match self {
Self::Spacing(v) => write!(f, "Spacing({:?})", v),
Self::Any(node, _) => node.fmt(f),
}
}
}
/// Performs stack layout.
struct StackLayouter<'a> {
/// The stack node to layout.
stack: &'a StackNode,
/// The axis of the block direction.
axis: SpecAxis,
/// Whether the stack should expand to fill the region.
expand: Spec<bool>,
/// The region to layout into.
regions: Regions,
/// The full size of `regions.current` that was available before we started
/// subtracting.
full: Size,
/// The generic size used by the frames for the current region.
used: Gen<Length>,
/// The alignment ruler for the current region.
ruler: Align,
/// Offset, alignment and frame for all children that fit into the current
/// region. The exact positions are not known yet.
frames: Vec<(Length, Align, Rc<Frame>)>,
/// Finished frames for previous regions.
finished: Vec<Constrained<Rc<Frame>>>,
}
impl<'a> StackLayouter<'a> {
/// Create a new stack layouter.
fn new(stack: &'a StackNode, mut regions: Regions) -> Self {
let axis = stack.dir.axis();
let full = regions.current;
let expand = regions.expand;
// Disable expansion along the block axis for children.
regions.expand.set(axis, false);
Self {
stack,
axis,
expand,
regions,
full,
used: Gen::zero(),
ruler: Align::Start,
frames: vec![],
finished: vec![],
}
}
/// Layout all children.
fn layout(mut self, ctx: &mut LayoutContext) -> Vec<Constrained<Rc<Frame>>> {
for child in &self.stack.children {
match *child {
StackChild::Spacing(amount) => self.space(amount),
StackChild::Any(ref node, align) => {
let frames = node.layout(ctx, &self.regions);
let len = frames.len();
for (i, frame) in frames.into_iter().enumerate() {
self.push_frame(frame.item, align);
if i + 1 < len {
self.finish_region();
}
}
}
}
}
self.finish_region();
self.finished
}
/// Add block-axis spacing into the current region.
fn space(&mut self, amount: Linear) {
// Resolve the linear.
let full = self.full.get(self.axis);
let resolved = amount.resolve(full);
// Cap the spacing to the remaining available space. This action does
// not directly affect the constraints because of the cap.
let remaining = self.regions.current.get_mut(self.axis);
let capped = resolved.min(*remaining);
// Grow our size and shrink the available space in the region.
self.used.block += capped;
*remaining -= capped;
}
/// Push a frame into the current region.
fn push_frame(&mut self, frame: Rc<Frame>, align: Align) {
// Grow our size.
let offset = self.used.block;
let size = frame.size.to_gen(self.axis);
self.used.block += size.block;
self.used.inline.set_max(size.inline);
self.ruler = self.ruler.max(align);
// Remember the frame and shrink available space in the region for the
// following children.
self.frames.push((offset, self.ruler, frame));
*self.regions.current.get_mut(self.axis) -= size.block;
}
/// Finish the frame for one region.
fn finish_region(&mut self) {
// Determine the stack's size dependening on whether the region expands.
let used = self.used.to_size(self.axis);
let size = Size::new(
if self.expand.x { self.full.w } else { used.w },
if self.expand.y { self.full.h } else { used.h },
);
let mut output = Frame::new(size, size.h);
let mut first = true;
// Place all frames.
for (offset, align, frame) in self.frames.drain(..) {
let stack_size = size.to_gen(self.axis);
let child_size = frame.size.to_gen(self.axis);
// Align along the block axis.
let block = align.resolve(
self.stack.dir,
if self.stack.dir.is_positive() {
offset .. stack_size.block - self.used.block + offset
} else {
let offset_with_self = offset + child_size.block;
self.used.block - offset_with_self
.. stack_size.block - offset_with_self
},
);
let pos = Gen::new(Length::zero(), block).to_point(self.axis);
// The baseline of the stack is that of the first frame.
if first {
output.baseline = pos.y + frame.baseline;
first = false;
}
output.push_frame(pos, frame);
}
// Generate tight constraints for now.
let mut cts = Constraints::new(self.expand);
cts.exact = self.full.to_spec().map(Some);
cts.base = self.regions.base.to_spec().map(Some);
self.regions.next();
self.full = self.regions.current;
self.used = Gen::zero();
self.ruler = Align::Start;
self.finished.push(output.constrain(cts));
}
}
|
