//! solver3/mod.rs

//!

//! Next-generation CSS layout engine with proper formatting context separation

pub mod cache;

pub mod calc;

pub mod counters;

pub mod display_list;

pub mod fc;

pub mod geometry;

pub mod getters;

pub mod layout_tree;

pub mod paged_layout;

pub mod pagination;

pub mod positioning;

pub mod scrollbar;

pub mod sizing;

pub mod taffy_bridge;

/// Lazy debug_info macro - only evaluates format args when debug_messages is Some

#[macro_export]

macro_rules! debug_info {

    ($ctx:expr, $($arg:tt)*) => {

        if $ctx.debug_messages.is_some() {

            $ctx.debug_info_inner(format!($($arg)*));

        }

    };

}

/// Lazy debug_warning macro - only evaluates format args when debug_messages is Some

#[macro_export]

macro_rules! debug_warning {

    ($ctx:expr, $($arg:tt)*) => {

        if $ctx.debug_messages.is_some() {

            $ctx.debug_warning_inner(format!($($arg)*));

        }

    };

}

/// Lazy debug_error macro - only evaluates format args when debug_messages is Some

#[macro_export]

macro_rules! debug_error {

    ($ctx:expr, $($arg:tt)*) => {

        if $ctx.debug_messages.is_some() {

            $ctx.debug_error_inner(format!($($arg)*));

        }

    };

}

/// Lazy debug_log macro - only evaluates format args when debug_messages is Some

#[macro_export]

macro_rules! debug_log {

    ($ctx:expr, $($arg:tt)*) => {

        if $ctx.debug_messages.is_some() {

            $ctx.debug_log_inner(format!($($arg)*));

        }

    };

}

/// Lazy debug_box_props macro - only evaluates format args when debug_messages is Some

#[macro_export]

macro_rules! debug_box_props {

    ($ctx:expr, $($arg:tt)*) => {

        if $ctx.debug_messages.is_some() {

            $ctx.debug_box_props_inner(format!($($arg)*));

        }

    };

}

/// Lazy debug_css_getter macro - only evaluates format args when debug_messages is Some

#[macro_export]

macro_rules! debug_css_getter {

    ($ctx:expr, $($arg:tt)*) => {

        if $ctx.debug_messages.is_some() {

            $ctx.debug_css_getter_inner(format!($($arg)*));

        }

    };

}

/// Lazy debug_bfc_layout macro - only evaluates format args when debug_messages is Some

#[macro_export]

macro_rules! debug_bfc_layout {

    ($ctx:expr, $($arg:tt)*) => {

        if $ctx.debug_messages.is_some() {

            $ctx.debug_bfc_layout_inner(format!($($arg)*));

        }

    };

}

/// Lazy debug_ifc_layout macro - only evaluates format args when debug_messages is Some

#[macro_export]

macro_rules! debug_ifc_layout {

    ($ctx:expr, $($arg:tt)*) => {

        if $ctx.debug_messages.is_some() {

            $ctx.debug_ifc_layout_inner(format!($($arg)*));

        }

    };

}

/// Lazy debug_table_layout macro - only evaluates format args when debug_messages is Some

#[macro_export]

macro_rules! debug_table_layout {

    ($ctx:expr, $($arg:tt)*) => {

        if $ctx.debug_messages.is_some() {

            $ctx.debug_table_layout_inner(format!($($arg)*));

        }

    };

}

/// Lazy debug_display_type macro - only evaluates format args when debug_messages is Some

#[macro_export]

macro_rules! debug_display_type {

    ($ctx:expr, $($arg:tt)*) => {

        if $ctx.debug_messages.is_some() {

            $ctx.debug_display_type_inner(format!($($arg)*));

        }

    };

}

use std::{collections::{BTreeMap, HashMap}, sync::Arc};

use azul_core::{

    dom::{DomId, NodeId},

    geom::{LogicalPosition, LogicalRect, LogicalSize},

    hit_test::{DocumentId, ScrollPosition},

    resources::RendererResources,

    selection::{TextCursor, TextSelection},

    styled_dom::StyledDom,

};

/// Sentinel value for "position not yet computed". No real position is ever f32::MIN.

pub const POSITION_UNSET: LogicalPosition = LogicalPosition { x: f32::MIN, y: f32::MIN };

/// Maximum number of scrollbar-induced reflow iterations before layout gives up.

/// Scrollbar appearance can change container size, which may trigger further scrollbar

/// changes. This limit prevents infinite loops in pathological layouts.

const MAX_SCROLLBAR_REFLOW_ITERATIONS: usize = 10;

/// Vec-based position storage indexed by layout-tree node index.

/// Replaces `BTreeMap<usize, LogicalPosition>` for O(1) access and cache-friendly iteration.

pub type PositionVec = Vec<LogicalPosition>;

/// Create a new PositionVec pre-sized for the given number of nodes.

#[inline]

/// Get position for node index, returning None if unset.

///

/// Note: only the `x` component is checked against the sentinel. This is sufficient

/// because `POSITION_UNSET` always sets both `x` and `y` to `f32::MIN`, and `pos_set`

/// always writes both components together.

#[inline(always)]

/// Set position for node index. Grows the vec if needed.

#[inline(always)]

/// Check if position has been set for node index.

#[inline(always)]

use azul_css::{

    props::property::{CssProperty, CssPropertyCategory},

    LayoutDebugMessage, LayoutDebugMessageType,

};

use self::{

    display_list::generate_display_list,

    geometry::IntrinsicSizes,

    getters::get_writing_mode,

    layout_tree::{generate_layout_tree, LayoutTree},

    sizing::calculate_intrinsic_sizes,

};

#[cfg(feature = "text_layout")]

pub use crate::font_traits::TextLayoutCache;

use crate::{

    font_traits::ParsedFontTrait,

    solver3::{

        cache::LayoutCache,

        display_list::DisplayList,

        fc::{LayoutConstraints, LayoutResult},

        layout_tree::DirtyFlag,

    },

};

/// A map of hashes for each node to detect changes in content like text.

pub type NodeHashMap = BTreeMap<usize, u64>;

/// Central context for a single layout pass.

pub struct LayoutContext<'a, T: ParsedFontTrait> {

    pub styled_dom: &'a StyledDom,

    #[cfg(feature = "text_layout")]

    pub font_manager: &'a crate::font_traits::FontManager<T>,

    #[cfg(not(feature = "text_layout"))]

    pub font_manager: core::marker::PhantomData<&'a T>,

    /// Text selections for rendering highlights. Populated from MultiCursorState.

    pub text_selections: &'a BTreeMap<DomId, TextSelection>,

    pub debug_messages: &'a mut Option<Vec<LayoutDebugMessage>>,

    pub counters: &'a mut HashMap<(usize, String), i32>,

    pub viewport_size: LogicalSize,

    /// Fragmentation context for CSS Paged Media (PDF generation)

    /// When Some, layout respects page boundaries and generates one DisplayList per page

    pub fragmentation_context: Option<&'a mut crate::paged::FragmentationContext>,

    /// Whether the text cursor should be drawn (managed by CursorManager blink timer)

    /// When false, the cursor is in the "off" phase of blinking and should not be rendered.

    /// When true (default), the cursor is visible.

    pub cursor_is_visible: bool,

    /// All active cursor locations from MultiCursorState / CursorManager.

    /// Each entry is (dom_id, node_id, cursor). Multiple entries = multi-cursor mode.

    /// Empty = no active cursor. The last entry is the primary cursor.

    pub cursor_locations: Vec<(DomId, NodeId, TextCursor)>,

    /// IME preedit (composition) text to render inline at the cursor position.

    /// When Some, the text should be rendered with an underline decoration.

    pub preedit_text: Option<String>,

    /// Text content overrides from in-progress edits (dirty_text_nodes).

    /// When a text node has been edited but not yet committed to the DOM,

    /// the layout pipeline should read from here instead of StyledDom.

    /// Key: (DomId, NodeId of the text node), Value: the edited text string.

    pub dirty_text_overrides: BTreeMap<(DomId, NodeId), String>,

    /// Per-node multi-slot cache (Taffy-inspired 9+1 architecture).

    /// Moved out of LayoutCache via std::mem::take for the duration of layout,

    /// then moved back after the layout pass completes.

    pub cache_map: cache::LayoutCacheMap,

    /// Image cache for resolving `background-image: url(...)` references.

    pub image_cache: &'a azul_core::resources::ImageCache,

    /// System style containing colors, fonts, metrics, and theme information.

    /// Used for selection colors, caret styling, and other system-themed elements.

    pub system_style: Option<std::sync::Arc<azul_css::system::SystemStyle>>,

    /// Callback to get the current system time. Used for profiling inside layout.

    /// On WASM targets (where `std::time::Instant::now()` panics), callers should

    /// supply a no-op or platform-specific implementation.

    pub get_system_time_fn: azul_core::task::GetSystemTimeCallback,

    /// Memoised `get_scrollbar_style` results, keyed by DOM node id.

    /// `compute_scrollbar_info_core` is called many times per node

    /// per layout pass (BFC path + Taffy flex/grid path + display

    /// list), and each call previously did 9 cascade walks. Once

    /// populated, subsequent callers in the same LayoutContext

    /// (a single render) return a clone.

    ///

    /// Uses `RefCell` so shared `&self` borrows (e.g. in the Taffy

    /// bridge's `get_core_container_style`) can mutate the cache

    /// without lifting the ctx to `&mut`. Keyed by `NodeId` so

    /// entries span DOMs in iframe-style nested documents if that

    /// ever becomes a thing.

    pub scrollbar_style_cache:

        core::cell::RefCell<std::collections::HashMap<NodeId, crate::solver3::getters::ComputedScrollbarStyle>>,

}

impl<'a, T: ParsedFontTrait> LayoutContext<'a, T> {

    /// Check if debug messages are enabled (for use with lazy macros)

    #[inline]

    /// Internal method - called by debug_log! macro after checking has_debug()

    #[inline]

    /// Internal method - called by debug_info! macro after checking has_debug()

    #[inline]

    /// Internal method - called by debug_warning! macro after checking has_debug()

    #[inline]

    /// Internal method - called by debug_error! macro after checking has_debug()

    #[inline]

    /// Internal method - called by debug_box_props! macro after checking has_debug()

    #[inline]

    /// Internal method - called by debug_css_getter! macro after checking has_debug()

    #[inline]

    /// Internal method - called by debug_bfc_layout! macro after checking has_debug()

    #[inline]

    /// Internal method - called by debug_ifc_layout! macro after checking has_debug()

    #[inline]

    /// Internal method - called by debug_table_layout! macro after checking has_debug()

    #[inline]

    /// Internal method - called by debug_display_type! macro after checking has_debug()

    #[inline]

    // Convenience wrappers (prefer debug_*! macros for lazy evaluation)

    #[inline]

    #[inline]

    #[inline]

    #[inline]

    #[inline]

    #[inline]

    #[inline]

    #[inline]

    #[inline]

    #[inline]

}

/// Main entry point for the incremental, cached layout engine.

///

/// `new_dom` is borrowed, not owned — every use inside is `&new_dom`,

/// so taking ownership was a pure formality that forced every caller

/// to `styled_dom.clone()` the DOM before calling. The clone was

/// ~2 MiB per render on excel.html; kept at the borrow now.

#[cfg(feature = "text_layout")]

/// Web-backend opt-out for display-list generation.

///

/// When set, [`layout_document`] runs the full positioning pipeline

/// (intrinsic sizing, taffy block/flex/grid, relative/sticky/absolute

/// adjustment → `calculated_positions`) but **skips

/// `generate_display_list`**, returning an empty [`DisplayList`]. The

/// web backend emits TLV DOM patches, not a display list, so it needs

/// the geometry in `calculated_positions` but nothing the painter

/// produces. This also lets the AArch64→wasm lift drop the entire

/// `display_list` painter surface (those symbols are classified `Leaf`

/// in `dll/src/web/symbol_table.rs::classify_for_name`, so the

/// transitive lifter never descends into them). Defaults `false` →

/// desktop/native behaviour is unchanged.

pub static SKIP_DISPLAY_LIST: core::sync::atomic::AtomicBool =

    core::sync::atomic::AtomicBool::new(false);

/// Set [`SKIP_DISPLAY_LIST`]. Provided as a function (rather than the

/// caller touching the static directly) so the web backend's

/// `dll`-crate caller reaches it through a normal `bl` into this

/// `azul_layout` function — keeping the static's address computation

/// intra-crate (direct `adrp+add`) instead of a cross-crate GOT load,

/// which the AArch64→wasm lift mirrors more reliably.

// M12.7: keep this out-of-line so the web lift sees it as its own wasm fn

// (not inlined into layout_dom_recursive). An opt-folded infinite loop in the

// solver (a mis-lifted loop exit) is otherwise hidden inside the giant inlined

// layout_dom_recursive; de-inlining lets AZ_FUEL/AZ_WASM_DEBUG name the actual

// source fn — and may itself prevent the inlining-induced fold. No perf cost on

// desktop (called once per layout).

#[inline(never)]

    // Reset IFC ID counter at the start of each layout pass

    // This ensures IFCs get consistent IDs across frames when the DOM structure is stable

    // in layout_document returns the rc=5 Err (the error enum can't be captured

    // reliably in the lift). The last value seen = the step that errored next.

    // If 0 here → the LogicalRect HFA arg was lost across the lifted call.

    // Create temporary context without counters for tree generation

    // --- Step 0: record DOM pointer / viewport for diagnostics only ---

    //

    // NOTE: there is intentionally NO pointer-identity fast path here.

    // Comparing `new_dom as *const StyledDom as usize` against a stored

    // pointer is UNSOUND across layout passes: each `regenerate_layout`

    // builds a fresh `StyledDom`, and after the previous one is dropped

    // (e.g. `layout_and_generate_display_list` calls `layout_results.clear()`

    // before re-laying out), the allocator/stack frequently hands the new,

    // *different* StyledDom the SAME address. A pointer match therefore does

    // NOT prove the content is unchanged — it would return the previous

    // frame's display list for a structurally different DOM (e.g. an image

    // removed from the tree would still appear in `scan_used_images`,

    // breaking resource GC). The Step 1.1 structural-identity cache below

    // (root `subtree_hash` + viewport) is the correct, content-based skip;

    // it costs one ~600 µs reconcile pass but cannot be fooled by address

    // reuse.

    // --- Step 1: Reconciliation & Invalidation ---

    // --- Step 1.1: Structural-identity display-list cache ---

    //

    // If the reconciled root subtree_hash matches the cached one AND

    // the viewport is unchanged, nothing structural has moved — skip

    // layout, positioning, AND display-list generation and return

    // the cached display list verbatim.

    //

    // This fires on re-renders of an unchanged DOM: the reconcile

    // pass still walks and hashes the tree, but that's ~600 µs vs

    // the ~4 ms it would otherwise cost to re-emit the display list.

    // Step 1.2: Clear Taffy Caches for Dirty Nodes

    }

    // Step 1.3: Compute CSS Counters

    // This must be done after tree generation but before layout,

    // as list markers need counter values during formatting context layout

    // Step 1.4: Resize and invalidate per-node cache (Taffy-inspired 9+1 slot cache)

    // Move cache_map out of LayoutCache for the duration of layout (avoids borrow conflicts).

    // It will be moved back after the layout pass completes.

    //

    // Critically: the old `cache_map.entries` is indexed by OLD

    // layout-tree positions. The NEW tree may have re-ordered

    // indices (anonymous wrapper slots shifted, whitespace nodes

    // dropped, etc.). A plain `resize_with(default)` would silently

    // serve the wrong node's cached result for any shifted index.

    //

    // Re-map by stable identity: build `old_layout_idx → new_layout_idx`

    // via the `(dom_node_id → layout_idx)` tables on both trees,

    // then move each surviving cache entry into its new slot. Nodes

    // without a matching DOM id (pure anonymous wrappers) fall

    // through to the default (empty, i.e. dirty) entry.

        // Primary mapping: DOM id → layout idx on both sides. This

        // covers every node that has a corresponding DOM node.

            };

                };

                {

            }

        }

        // Secondary mapping: anonymous wrappers (dom_node_id == None)

        // by (parent_new_idx, ordinal-among-anon-siblings). An

        // unchanged DOM produces the same anon wrappers in the same

        // order under the same parent — matching by position here

        // preserves their cache slots too. Without this, anon

        // wrappers re-allocate empty every reconcile and invalidate

        // their ancestors via `mark_dirty`.

            }

        // Build old-parent → [old_anon_indices] and

        // new-parent → [new_anon_indices]; match by pair position.

        // For each new parent we know: look up its old twin by the

        // dom-id mapping we just populated, then match anon children

        // positionally within that parent.

        // Build a new→old layout-idx lookup from the primary pass.

            };

            }

        }

            };

            };

                };

                {

            }

        }

    // Now create the real context with computed counters

    // --- Step 1.5: Early Exit Optimization ---

    // M12.7: `&& cache.tree.is_some()` — this "nothing changed, reuse cached

    // layout" fast path REQUIRES a cached tree; on COLD layout cache.tree is

    // None, so entering here would hit `ok_or(InvalidTree)`. recon_result must

    // be dirty on cold (the viewport-resize dirties the root), but if

    // is_clean() mis-evaluates we'd wrongly early-exit → InvalidTree. Guarding

    // on a cached tree is both correct (can't reuse what isn't there) and

    // robust. (rc=5 post-reconcile, step=2: this was the failing `?`.)

        // Use cached scroll IDs if available, otherwise compute them

            use crate::window::LayoutWindow;

        } else {

        };

        );

    // --- Step 2: Incremental Layout Loop (handles scrollbar-induced reflows) ---

    loop {

        };

        {

        }

        // divergence is inside calculate_intrinsic_sizes (the SIMD/text intrinsic pass).

            // 0x05, the divergence is INSIDE get_containing_block_for_node (or the for-loop

            // entry); if 0x53 but not 0x55, it's the margin logic / box_props.unpack below.

            // get_containing_block_for_node(viewport)). 800 here but viewport=800 ⟹ OK;

            // 0 here with viewport=800 ⟹ get_containing_block_for_node lost it (HFA return).

            // For ROOT nodes (no parent), we need to account for their margin.

            // The containing block position from viewport is (0, 0), but the root's

            // content starts at (margin + border + padding, margin + border + padding).

            // We pass margin-adjusted position so calculate_content_box_pos works correctly.

                )

            } else {

            };

            // DEBUG: Log containing block info for this root

                        root_idx,

                        dom_name,

                        cb_pos.x,

                        cb_pos.y,

                        adjusted_cb_pos.x,

                        adjusted_cb_pos.y,

                        cb_size.width,

                        cb_size.height,

                        viewport.size.width,

                        viewport.size.height,

                        root_bp.margin.left,

                        root_bp.margin.top

                    ),

                ));

            // Purge after intrinsic sizing — frees child_intrinsics Vecs,

            // IntrinsicSizeCalculator temporaries, text measurement caches.

            // 0x57 = it RETURNED. If step stays 0x55, calculate_layout_for_subtree diverges.

            // This is exactly what calc_used_size reads as `viewport`. 0 here pinpoints the

            // loss to the ctx build (viewport.size → ctx.viewport_size copy).

            // 0x5E = Err. Do NOT propagate (continue to the cache store) so layout-real can

            // see whether the geometry was computed regardless of a (possibly spurious,

            // niche-Result-mis-discriminated) Err.

                )

            };

            // CRITICAL: Insert the root node's own position into calculated_positions

            // This is necessary because calculate_layout_for_subtree only inserts

            // positions for children, not for the root itself.

            //

            // For root nodes, the position should be at (margin.left, margin.top) relative

            // to the viewport origin, because the margin creates space between the viewport

            // edge and the element's border-box.

                // Calculate the root's border-box position by adding margins to viewport origin

                // This is different from non-root nodes which inherit their position from

                // their containing block.

                );

                // DEBUG: Log root positioning

                            root_idx,

                            dom_name,

                            root_position.x,

                            root_position.y,

                            root_bp2.margin.top,

                            root_bp2.margin.right,

                            root_bp2.margin.bottom,

                            root_bp2.margin.left

                        ),

                    ));

        }

        // (step 6). If step stays 5, the divergence is in calculate_layout_for_subtree.

                loop_count

            );

    }

    // +spec:positioning:8d1286 - normal flow, relative, float, absolute positioning dispatch

    // +spec:positioning:bdfc81 - Layout divided into sizing (Step 2) then positioning (Step 3)

    // --- Step 3: Adjust Relatively Positioned Elements ---

    // +spec:positioning:a831e8 - inline content width uses pre-relative-offset positions (satisfied by post-layout relative adjustment)

    // +spec:positioning:e2647b - Relative positioning applied after line height calculation, so line height is not adjusted for relative offsets

    // +spec:positioning:77a2d2 - Relatively positioned boxes considered without their offset during auto height

    // +spec:positioning:b47ac2 - Relatively positioned boxes considered without their offset for block auto height

    // Relative offsets applied AFTER layout, so auto-height calculation sees normal-flow positions.

    // This must be done BEFORE positioning out-of-flow elements, because

    // relatively positioned elements establish containing blocks for their

    // absolutely positioned descendants. If we adjust relative positions after

    // positioning absolute elements, the absolute elements will be positioned

    // relative to the wrong (pre-adjustment) position of their containing block.

    // Pass the viewport to correctly resolve percentage offsets for the root element.

    {

    }

    // --- Step 3.25: Adjust Sticky Positioned Elements ---

    // Sticky elements are laid out in normal flow, then their visual position

    // is clamped based on scroll offset and inset properties relative to the

    // nearest scrollport. Must happen after relative positioning but before

    // absolute positioning (sticky elements establish containing blocks).

    {

    }

    // --- Step 3.5: Position Out-of-Flow Elements ---

    // This must be done AFTER adjusting relative positions, so that absolutely

    // positioned elements are positioned relative to the final (post-adjustment)

    // position of their relatively positioned containing blocks.

    {

    }

    // --- Step 3.75: Compute Stable Scroll IDs ---

    // This must be done AFTER layout but BEFORE display list generation

    use crate::window::LayoutWindow;

    // --- Step 4: Generate Display List & Update Cache ---

        // Web backend: positions are done; the painter is dead weight.

    } else {

    };

    // Move cache_map back into LayoutCache before dropping ctx

    // Cache the freshly-generated display list keyed on the root's

    // subtree_hash + viewport. If the next `layout_document` call

    // sees matching values after reconcile, it returns this clone

    // directly and skips all downstream work.

    // + calculated_positions.len in the low bits. If step stays 3, it diverged earlier.

// +spec:containing-block:159830 - Containing block chain: parent content-box for in-flow, viewport for initial containing block

// +spec:containing-block:22fbaa - computes the element's original containing block (before positioning effects)

// +spec:containing-block:238fc5 - containing block dimensions calculated here (CSS 2.2 §9.1.2 forward ref to §10)

// +spec:containing-block:263629 - block element's content-box establishes the containing block for its line boxes

// +spec:containing-block:2a5280 - boxes act as containing blocks for descendants; CB = parent's content box

// +spec:containing-block:6776cb - boxes positioned w.r.t. containing block but not confined; overflow allowed

// +spec:containing-block:718894 - CB derived from parent content-box edges; root uses initial CB (viewport)

// +spec:containing-block:a2aa37 - box edges act as containing block for descendants; initial containing block = viewport

// +spec:containing-block:e23b3f - CSS 2.2 §10.1: initial containing block = viewport; static/relative = parent content-box; fixed = viewport

// +spec:containing-block:e8fdb2 - Containing block resolution (CSS2 §9.1.2, §10.1)

// +spec:overflow:9a2b11 - containing block is content-box of parent; boxes may overflow it

// +spec:positioning:acc663 - containing block definition: element boxes positioned relative to containing block

            // Position in calculated_positions is the margin-box position

            // To get content-box, add: border + padding (NOT margin, that's already in pos)

            );

                // +spec:containing-block:c205e5 - writing mode of containing block used for inner_size (orthogonal flow awareness)

    // +spec:containing-block:41bdfc - ICB equals viewport; overflow:hidden on root clips to ICB

    // +spec:containing-block:1eed60 - Initial containing block establishes a BFC; viewport is the ICB

    // +spec:containing-block:99866f - Containing block is a rectangle for sizing/positioning; ICB from viewport

    // +spec:containing-block:22f09b - viewport serves as initial containing block for root element

    // Root element's containing block is the initial containing block (CSS 2.2 §10.1, CSS Display 3 §2.8).

    // +spec:containing-block:2fd7b1 - ICB equals viewport; principal writing mode propagated to ICB

    // Root element's containing block is the initial containing block (CSS 2.2 §10.1, CSS Display 3 §2.8).

    // The principal writing mode is propagated to the ICB and viewport (css-writing-modes-4 §8.1).

    // +spec:containing-block:5efb84 - Root element's containing block is the initial containing block

    // +spec:containing-block:6278fb - initial containing block is the viewport; also serves as initial fixed containing block

    // Root element's containing block is the initial containing block (CSS 2.2 §10.1, CSS Display 3 §2.8).

    // For ROOT nodes: the containing block is the viewport (initial containing block).

    // Do NOT subtract margin here - margins are handled in calculate_used_size().

    // The margin creates space between viewport edge and element's border-box,

    // but the available space for calculating width/height percentages

    // is still the full viewport size.

#[derive(Debug)]

pub enum LayoutError {

    InvalidTree,

    SizingFailed,

    PositioningFailed,

    DisplayListFailed,

    Text(crate::font_traits::LayoutError),

}

impl std::fmt::Display for LayoutError {

        }

}

impl From<crate::font_traits::LayoutError> for LayoutError {

}

impl std::error::Error for LayoutError {}

pub type Result<T> = std::result::Result<T, LayoutError>;