custom_tree_vec.rs

mod common {
    pub mod image;
    pub mod text;
}
use common::image::{image_measure_function, ImageContext};
use common::text::{text_measure_function, FontMetrics, TextContext, WritingMode, LOREM_IPSUM};
use taffy::util::print_tree;
use taffy::{
    compute_cached_layout, compute_flexbox_layout, compute_grid_layout, compute_leaf_layout, compute_root_layout,
    prelude::*, round_layout, Cache, CacheTree,
};

#[derive(Debug, Copy, Clone)]
#[allow(dead_code)]
enum NodeKind {
    Flexbox,
    Grid,
    Text,
    Image,
}

struct Node {
    kind: NodeKind,
    style: Style,
    text_data: Option<TextContext>,
    image_data: Option<ImageContext>,
    cache: Cache,
    unrounded_layout: Layout,
    final_layout: Layout,
    children: Vec<usize>,
    hoisted_children: Vec<NodeId>,
}

impl Default for Node {
    fn default() -> Self {
        Node {
            kind: NodeKind::Flexbox,
            style: Style::default(),
            text_data: None,
            image_data: None,
            cache: Cache::new(),
            unrounded_layout: Layout::with_order(0),
            final_layout: Layout::with_order(0),
            children: Vec::new(),
            hoisted_children: Vec::new(),
        }
    }
}

#[allow(dead_code)]
impl Node {
    pub fn new_row(style: Style) -> Node {
        Node {
            kind: NodeKind::Flexbox,
            style: Style { display: Display::Flex, flex_direction: FlexDirection::Row, ..style },
            ..Node::default()
        }
    }
    pub fn new_column(style: Style) -> Node {
        Node {
            kind: NodeKind::Flexbox,
            style: Style { display: Display::Flex, flex_direction: FlexDirection::Column, ..style },
            ..Node::default()
        }
    }
    pub fn new_grid(style: Style) -> Node {
        Node { kind: NodeKind::Grid, style: Style { display: Display::Grid, ..style }, ..Node::default() }
    }
    pub fn new_text(style: Style, text_data: TextContext) -> Node {
        Node { kind: NodeKind::Text, style, text_data: Some(text_data), ..Node::default() }
    }
    pub fn new_image(style: Style, image_data: ImageContext) -> Node {
        Node { kind: NodeKind::Image, style, image_data: Some(image_data), ..Node::default() }
    }
}

struct Tree {
    nodes: Vec<Node>,
}

impl Tree {
    pub fn new() -> Tree {
        Tree { nodes: Vec::new() }
    }

    pub fn add_node(&mut self, node: Node) -> usize {
        self.nodes.push(node);
        self.nodes.len() - 1
    }

    pub fn append_child(&mut self, parent: usize, child: usize) {
        self.nodes[parent].children.push(child);
    }

    #[inline(always)]
    fn node_from_id(&self, node_id: NodeId) -> &Node {
        &self.nodes[usize::from(node_id)]
    }

    #[inline(always)]
    fn node_from_id_mut(&mut self, node_id: NodeId) -> &mut Node {
        &mut self.nodes[usize::from(node_id)]
    }

    pub fn compute_layout(&mut self, root: usize, available_space: Size<AvailableSpace>, use_rounding: bool) {
        compute_root_layout(self, NodeId::from(root), available_space);
        if use_rounding {
            round_layout(self, NodeId::from(root))
        }
    }

    pub fn print_tree(&mut self, root: usize) {
        print_tree(self, NodeId::from(root));
    }
}

struct ChildIter<'a>(std::slice::Iter<'a, usize>);
impl Iterator for ChildIter<'_> {
    type Item = NodeId;
    fn next(&mut self) -> Option<Self::Item> {
        self.0.next().copied().map(NodeId::from)
    }
}

impl taffy::TraversePartialTree for Tree {
    type ChildIter<'a> = ChildIter<'a>;

    fn child_ids(&self, node_id: NodeId) -> Self::ChildIter<'_> {
        ChildIter(self.node_from_id(node_id).children.iter())
    }

    fn child_count(&self, node_id: NodeId) -> usize {
        self.node_from_id(node_id).children.len()
    }

    fn get_child_id(&self, node_id: NodeId, index: usize) -> NodeId {
        NodeId::from(self.node_from_id(node_id).children[index])
    }
}

impl taffy::TraverseTree for Tree {}

impl taffy::LayoutPartialTree for Tree {
    type CustomIdent = String;

    type CoreContainerStyle<'a>
        = &'a Style
    where
        Self: 'a;

    fn get_core_container_style(&self, node_id: NodeId) -> Self::CoreContainerStyle<'_> {
        &self.node_from_id(node_id).style
    }

    fn set_unrounded_layout(&mut self, node_id: NodeId, layout: &Layout) {
        self.node_from_id_mut(node_id).unrounded_layout = *layout;
    }

    fn resolve_calc_value(&self, _val: *const (), _basis: f32) -> f32 {
        0.0
    }

    fn compute_child_layout(&mut self, node_id: NodeId, inputs: taffy::tree::LayoutInput) -> taffy::tree::LayoutOutput {
        compute_cached_layout(self, node_id, inputs, |tree, node_id, inputs| {
            let node = &mut tree.nodes[usize::from(node_id)];
            let font_metrics = FontMetrics { char_width: 10.0, char_height: 10.0 };

            match node.kind {
                NodeKind::Flexbox => compute_flexbox_layout(tree, node_id, inputs),
                NodeKind::Grid => compute_grid_layout(tree, node_id, inputs),
                NodeKind::Text => compute_leaf_layout(
                    inputs,
                    &node.style,
                    |_val, _basis| 0.0,
                    |known_dimensions, available_space| {
                        text_measure_function(
                            known_dimensions,
                            available_space,
                            node.text_data.as_ref().unwrap(),
                            &font_metrics,
                        )
                    },
                ),
                NodeKind::Image => compute_leaf_layout(
                    inputs,
                    &node.style,
                    |_val, _basis| 0.0,
                    |known_dimensions, _available_space| {
                        image_measure_function(known_dimensions, node.image_data.as_ref().unwrap())
                    },
                ),
            }
        })
    }
}

impl taffy::LayoutContainingBlock for Tree {
    type OofItemStyle<'a>
        = &'a Style
    where
        Self: 'a;

    fn get_oof_item_style(&self, node_id: NodeId) -> Self::OofItemStyle<'_> {
        &self.node_from_id(node_id).style
    }

    fn set_hoisted_children(&mut self, node_id: NodeId, hoisted: &[NodeId]) {
        let vec = &mut self.node_from_id_mut(node_id).hoisted_children;
        vec.clear();
        vec.extend_from_slice(hoisted);
    }

    fn add_hoisted_children(&mut self, node_id: NodeId, hoisted: &[NodeId]) {
        self.node_from_id_mut(node_id).hoisted_children.extend_from_slice(hoisted);
    }
}

impl CacheTree for Tree {
    fn cache_get(&mut self, node_id: NodeId, inputs: &taffy::LayoutInput) -> Option<taffy::LayoutOutput> {
        self.node_from_id_mut(node_id).cache.get(inputs)
    }

    fn cache_store(&mut self, node_id: NodeId, inputs: &taffy::LayoutInput, layout_output: taffy::LayoutOutput) {
        self.node_from_id_mut(node_id).cache.store(inputs, layout_output)
    }

    fn cache_clear(&mut self, node_id: NodeId) {
        self.node_from_id_mut(node_id).cache.clear();
    }
}

impl taffy::LayoutFlexboxContainer for Tree {
    type FlexboxContainerStyle<'a>
        = &'a Style
    where
        Self: 'a;

    type FlexboxItemStyle<'a>
        = &'a Style
    where
        Self: 'a;

    fn get_flexbox_container_style(&self, node_id: NodeId) -> Self::FlexboxContainerStyle<'_> {
        &self.node_from_id(node_id).style
    }

    fn get_flexbox_child_style(&self, child_node_id: NodeId) -> Self::FlexboxItemStyle<'_> {
        &self.node_from_id(child_node_id).style
    }
}

impl taffy::LayoutGridContainer for Tree {
    type GridContainerStyle<'a>
        = &'a Style
    where
        Self: 'a;

    type GridItemStyle<'a>
        = &'a Style
    where
        Self: 'a;

    fn get_grid_container_style(&self, node_id: NodeId) -> Self::GridContainerStyle<'_> {
        &self.node_from_id(node_id).style
    }

    fn get_grid_child_style(&self, child_node_id: NodeId) -> Self::GridItemStyle<'_> {
        &self.node_from_id(child_node_id).style
    }
}

impl taffy::RoundTree for Tree {
    fn get_unrounded_layout(&self, node_id: NodeId) -> Layout {
        self.node_from_id(node_id).unrounded_layout
    }

    fn set_final_layout(&mut self, node_id: NodeId, layout: &Layout) {
        self.node_from_id_mut(node_id).final_layout = *layout;
    }

    fn is_hoisted(&self, node_id: NodeId) -> bool {
        self.node_from_id(node_id).style.position.is_out_of_flow()
    }

    fn hoisted_child_count(&self, node_id: NodeId) -> usize {
        self.node_from_id(node_id).hoisted_children.len()
    }

    fn get_hoisted_child_id(&self, node_id: NodeId, index: usize) -> NodeId {
        self.node_from_id(node_id).hoisted_children[index]
    }
}

impl taffy::PrintTree for Tree {
    fn get_debug_label(&self, node_id: NodeId) -> &'static str {
        match self.node_from_id(node_id).kind {
            NodeKind::Flexbox => "FLEX",
            NodeKind::Grid => "GRID",
            NodeKind::Text => "TEXT",
            NodeKind::Image => "IMAGE",
        }
    }

    fn get_final_layout(&self, node_id: NodeId) -> Layout {
        self.node_from_id(node_id).final_layout
    }
}

fn main() -> Result<(), taffy::TaffyError> {
    let mut tree = Tree::new();

    let root = Node::new_column(Style::DEFAULT);
    let root_id = tree.add_node(root);

    let text_node = Node::new_text(
        Style::default(),
        TextContext { text_content: LOREM_IPSUM.into(), writing_mode: WritingMode::Horizontal },
    );
    let text_node_id = tree.add_node(text_node);
    tree.append_child(root_id, text_node_id);

    let image_node = Node::new_image(Style::default(), ImageContext { width: 400.0, height: 300.0 });
    let image_node_id = tree.add_node(image_node);
    tree.append_child(root_id, image_node_id);

    // Compute layout and print result
    tree.compute_layout(root_id, Size::MAX_CONTENT, true);
    tree.print_tree(root_id);

    Ok(())
}