bliss_dom/

resolve.rs

//! Resolve style and layout

use std::{
    cell::RefCell,
    time::{SystemTime, UNIX_EPOCH},
};

use debug_timer::debug_timer;
use parley::LayoutContext;
use selectors::Element as _;
use style::dom::TDocument;

#[cfg(feature = "parallel-construct")]
use rayon::prelude::*;

// FIXME: static thread_local FontCtx isn't necessarily correct in multi-document context.
// Should use thread_local crate with ThreadLocal value store in the Document.
thread_local! {
    pub(crate) static LAYOUT_CTX: RefCell<Option<Box<LayoutContext<TextBrush>>>> = const { RefCell::new(None) };
}

#[cfg(feature = "incremental")]
use style::selector_parser::RestyleDamage;
use taffy::AvailableSpace;

use crate::{
    BaseDocument, NON_INCREMENTAL,
    events::ScrollAnimationState,
    layout::{
        construct::{
            ConstructionTask, ConstructionTaskData, ConstructionTaskResult,
            ConstructionTaskResultData, build_inline_layout_into, collect_layout_children,
        },
        damage::{ALL_DAMAGE, CONSTRUCT_BOX, CONSTRUCT_DESCENDENT, CONSTRUCT_FC},
    },
    node::TextBrush,
};

impl BaseDocument {
    /// Restyle the tree and then relayout it
    pub fn resolve(&mut self, current_time_for_animations: f64) {
        if TDocument::as_node(&&self.nodes[0])
            .first_element_child()
            .is_none()
        {
            println!("No DOM - not resolving");
            return;
        }

        // Process messages that have been sent to our message channel (e.g. loaded resource)
        self.handle_messages();

        self.resolve_scroll_animation();

        // D-2c-followup: root_element widened to Option<&Node>. The early
        // `is_none()` guard above ensures this branch is only taken when a root
        // element exists, so `unwrap_or(0)` is dead — but it's still the
        // compiler requirement. The guard above is now LOAD-BEARING for the
        // unwrap_or(0) safety: deleting it would silently propagate `0` to
        // `propagate_damage_flags` / `flush_styles_to_layout`, which would
        // compute layout against the document root node (id 0, an empty
        // layout block) producing garbage layout with no panic. The
        // debug_assert below catches a future refactor that breaks this
        // invariant on day 1.
        debug_assert!(
            self.root_element().is_some(),
            "resolve: 'no DOM' guard above lost its effect — root_element became None when an element child was expected"
        );
        let root_node_id = self.root_element().map(|r| r.id).unwrap_or(0);
        debug_timer!(timer, feature = "log_phase_times");

        // we need to resolve stylist first since it will need to drive our layout bits
        self.resolve_stylist(current_time_for_animations);
        timer.record_time("style");

        // Propagate damage flags (from mutation and restyles) up and down the tree
        #[cfg(feature = "incremental")]
        self.propagate_damage_flags(root_node_id, RestyleDamage::empty());
        #[cfg(feature = "incremental")]
        timer.record_time("damage");

        // Fix up tree for layout (insert anonymous blocks as necessary, etc)
        self.resolve_layout_children();
        timer.record_time("construct");

        self.resolve_deferred_tasks();
        timer.record_time("pconstruct");

        // Merge stylo into taffy
        self.flush_styles_to_layout(root_node_id);
        timer.record_time("flush");

        // Next we resolve layout with the data resolved by stlist
        self.resolve_layout();
        timer.record_time("layout");

        // Clear all damage and dirty flags
        #[cfg(feature = "incremental")]
        {
            for (_, node) in self.nodes.iter_mut() {
                node.clear_damage_mut();
                node.unset_dirty_descendants();
            }
            timer.record_time("c_damage");
        }

        let mut subdoc_is_animating = false;
        for &node_id in &self.sub_document_nodes {
            let node = &mut self.nodes[node_id];
            let size = node.final_layout.size;
            if let Some(mut sub_doc) = node.subdoc_mut().map(|doc| doc.inner_mut()) {
                // Set viewport
                // viewport_mut handles change detection. So we just unconditionally set the values;
                let mut sub_viewport = sub_doc.viewport_mut();
                sub_viewport.hidpi_scale = self.viewport.hidpi_scale;
                sub_viewport.zoom = self.viewport.zoom;
                sub_viewport.color_scheme = self.viewport.color_scheme;

                let viewport_scale = self.viewport.scale();
                sub_viewport.window_size = (
                    (size.width * viewport_scale) as u32,
                    (size.height * viewport_scale) as u32,
                );
                drop(sub_viewport);

                sub_doc.resolve(current_time_for_animations);

                subdoc_is_animating |= sub_doc.is_animating();
            }
        }
        self.subdoc_is_animating = subdoc_is_animating;
        timer.record_time("subdocs");

        timer.print_times(&format!("Resolve({}): ", self.id()));
    }

    pub fn resolve_scroll_animation(&mut self) {
        match &mut self.scroll_animation {
            ScrollAnimationState::Fling(fling_state) => {
                let time_ms = SystemTime::now()
                    .duration_since(UNIX_EPOCH)
                    .unwrap_or_default()
                    .as_millis() as u64 as f64;

                let time_diff_ms = time_ms - fling_state.last_seen_time;

                // 0.95 @ 60fps normalized to actual frame times
                let deceleration = 1.0 - ((0.05 / 16.66666) * time_diff_ms);

                fling_state.x_velocity *= deceleration;
                fling_state.y_velocity *= deceleration;
                fling_state.last_seen_time = time_ms;
                let fling_state = fling_state.clone();

                let dx = fling_state.x_velocity * time_diff_ms;
                let dy = fling_state.y_velocity * time_diff_ms;

                self.scroll_by(Some(fling_state.target), dx, dy, &mut |_| {});
                if fling_state.x_velocity.abs() < 0.1 && fling_state.y_velocity.abs() < 0.1 {
                    self.scroll_animation = ScrollAnimationState::None;
                }
            }
            ScrollAnimationState::None => {
                // Do nothing
            }
        }
    }

    /// Ensure that the layout_children field is populated for all nodes
    pub fn resolve_layout_children(&mut self) {
        resolve_layout_children_recursive(self, self.root_node().id);

        fn resolve_layout_children_recursive(doc: &mut BaseDocument, node_id: usize) {
            let mut damage = doc.nodes[node_id].damage().unwrap_or(ALL_DAMAGE);
            let _flags = doc.nodes[node_id].flags;

            if NON_INCREMENTAL || damage.intersects(CONSTRUCT_FC | CONSTRUCT_BOX) {
                //} || flags.contains(NodeFlags::IS_INLINE_ROOT) {
                let mut layout_children = Vec::new();
                let mut anonymous_block: Option<usize> = None;
                collect_layout_children(doc, node_id, &mut layout_children, &mut anonymous_block);

                // Recurse into newly collected layout children
                for child_id in layout_children.iter().copied() {
                    resolve_layout_children_recursive(doc, child_id);
                    doc.nodes[child_id].layout_parent.set(Some(node_id));
                    if let Some(data) = doc.nodes[child_id].stylo_element_data.get_mut() {
                        data.damage
                            .remove(CONSTRUCT_DESCENDENT | CONSTRUCT_FC | CONSTRUCT_BOX);
                    }
                }

                *doc.nodes[node_id].layout_children.borrow_mut() = Some(layout_children.clone());
                // *doc.nodes[node_id].paint_children.borrow_mut() = Some(layout_children);

                damage.remove(CONSTRUCT_DESCENDENT | CONSTRUCT_FC | CONSTRUCT_BOX);
                // damage.insert(RestyleDamage::RELAYOUT | RestyleDamage::REPAINT);
            } else {
                //if damage.contains(CONSTRUCT_DESCENDENT) {
                let layout_children = doc.nodes[node_id].layout_children.borrow_mut().take();
                if let Some(layout_children) = layout_children {
                    // Recurse into previously computed layout children
                    for child_id in layout_children.iter().copied() {
                        resolve_layout_children_recursive(doc, child_id);
                        doc.nodes[child_id].layout_parent.set(Some(node_id));
                    }

                    *doc.nodes[node_id].layout_children.borrow_mut() = Some(layout_children);
                }

                // damage.remove(CONSTRUCT_DESCENDENT);
                // damage.insert(RestyleDamage::RELAYOUT | RestyleDamage::REPAINT);
            }

            doc.nodes[node_id].set_damage(damage);
        }
    }

    pub fn resolve_deferred_tasks(&mut self) {
        let mut deferred_construction_nodes = std::mem::take(&mut self.deferred_construction_nodes);

        // Deduplicate deferred tasks by node_id to avoid redundant work
        deferred_construction_nodes.sort_unstable_by_key(|task| task.node_id);
        deferred_construction_nodes.dedup_by_key(|task| task.node_id);

        #[cfg(feature = "parallel-construct")]
        let iter = deferred_construction_nodes.into_par_iter();
        #[cfg(not(feature = "parallel-construct"))]
        let iter = deferred_construction_nodes.into_iter();

        let results: Vec<ConstructionTaskResult> = iter
            .map(|task: ConstructionTask| match task.data {
                ConstructionTaskData::InlineLayout(mut layout) => {
                    #[cfg(feature = "parallel-construct")]
                    let mut layout_ctx = LAYOUT_CTX
                        .take()
                        .unwrap_or_else(|| Box::new(LayoutContext::new()));
                    #[cfg(feature = "parallel-construct")]
                    let layout_ctx_mut = &mut layout_ctx;

                    #[cfg(feature = "parallel-construct")]
                    let mut font_ctx = self
                        .thread_font_contexts
                        .get_or(|| {
                            RefCell::new(Box::new(
                                self.font_ctx
                                    .lock()
                                    .unwrap_or_else(|e| e.into_inner())
                                    .clone(),
                            ))
                        })
                        .borrow_mut();
                    #[cfg(feature = "parallel-construct")]
                    let font_ctx_mut = &mut *font_ctx;

                    #[cfg(not(feature = "parallel-construct"))]
                    let layout_ctx_mut = &mut self.layout_ctx;
                    #[cfg(not(feature = "parallel-construct"))]
                    let font_ctx_mut =
                        &mut *self.font_ctx.lock().unwrap_or_else(|e| e.into_inner());

                    layout.content_widths = None;
                    build_inline_layout_into(
                        &self.nodes,
                        layout_ctx_mut,
                        font_ctx_mut,
                        &mut layout,
                        self.viewport.scale(),
                        task.node_id,
                    );

                    #[cfg(feature = "parallel-construct")]
                    {
                        LAYOUT_CTX.set(Some(layout_ctx));
                    }

                    // Pre-populate the content_widths cache. When there are no inline boxes,
                    // this is trivially safe and saves a Parley call during layout. When there
                    // ARE inline boxes, their sizes are not yet set (box sizing happens during
                    // compute_inline_layout_inner), so the cached widths may be stale — they
                    // will be recomputed on first access during layout. Only cache when no
                    // inline boxes are present (pure text runs) where box sizes are irrelevant.
                    if layout.layout.inline_boxes().is_empty() {
                        layout.content_widths();
                    }

                    ConstructionTaskResult {
                        node_id: task.node_id,
                        data: ConstructionTaskResultData::InlineLayout(layout),
                    }
                }
            })
            .collect();

        for result in results {
            match result.data {
                ConstructionTaskResultData::InlineLayout(layout) => {
                    self.nodes[result.node_id].cache.clear();
                    if let Some(elem) = self.nodes[result.node_id].element_data_mut() {
                        elem.inline_layout_data = Some(layout);
                    }
                }
            }
        }

        self.deferred_construction_nodes.clear();
    }

    /// Walk the nodes now that they're properly styled and transfer their styles to the taffy style system
    ///
    /// TODO: update taffy to use an associated type instead of slab key
    /// TODO: update taffy to support traited styles so we don't even need to rely on taffy for storage
    pub fn resolve_layout(&mut self) {
        let size = self.stylist.device().au_viewport_size();

        let available_space = taffy::Size {
            width: AvailableSpace::Definite(size.width.to_f32_px()),
            height: AvailableSpace::Definite(size.height.to_f32_px()),
        };

        // D-2c-followup: propagate the `Option<&Node>` widening; the early
        // guard above guarantees this `unwrap_or(0)` is unreachable, but the
        // compiler won't let us call `.id` on `Option<&Node>` anymore.
        debug_assert!(
            self.root_element().is_some(),
            "resolve_layout: 'no DOM' guard above lost its effect — root_element became None when an element child was expected"
        );
        let root_element_id =
            taffy::NodeId::from(self.root_element().map(|r| r.id).unwrap_or(0));

        // println!("\n\nRESOLVE LAYOUT\n===========\n");

        taffy::compute_root_layout(self, root_element_id, available_space);
        taffy::round_layout(self, root_element_id);

        // println!("\n\n");
        // taffy::print_tree(self, root_node_id)
    }
}