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we (web engine): Experimental web browser project to understand the limits of Claude
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Rust
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Block layout engine: box generation, block/inline layout, and text wrapping.//!//! Builds a layout tree from a styled tree (DOM + computed styles) and positions//! block-level elements vertically with proper inline formatting context.
use std::collections::HashMap;
use we_css::values::Color;use we_dom::{Document, NodeData, NodeId};use we_style::computed::{ BorderStyle, ComputedStyle, Display, LengthOrAuto, Overflow, Position, StyledNode, TextAlign, TextDecoration,};use we_text::font::Font;
/// Edge sizes for box model (margin, padding, border).#[derive(Debug, Clone, Copy, Default, PartialEq)]pub struct EdgeSizes { pub top: f32, pub right: f32, pub bottom: f32, pub left: f32,}
/// A positioned rectangle with content area dimensions.#[derive(Debug, Clone, Copy, Default, PartialEq)]pub struct Rect { pub x: f32, pub y: f32, pub width: f32, pub height: f32,}
/// The type of layout box.#[derive(Debug)]pub enum BoxType { /// Block-level box from an element. Block(NodeId), /// Inline-level box from an element. Inline(NodeId), /// A run of text from a text node. TextRun { node: NodeId, text: String }, /// Anonymous block wrapping inline content within a block container. Anonymous,}
/// A single positioned text fragment with its own styling.////// Multiple fragments can share the same y-coordinate when they are/// on the same visual line (e.g. `<p>Hello <em>world</em></p>` produces/// two fragments at the same y).#[derive(Debug, Clone, PartialEq)]pub struct TextLine { pub text: String, pub x: f32, pub y: f32, pub width: f32, pub font_size: f32, pub color: Color, pub text_decoration: TextDecoration, pub background_color: Color,}
/// A box in the layout tree with dimensions and child boxes.#[derive(Debug)]pub struct LayoutBox { pub box_type: BoxType, pub rect: Rect, pub margin: EdgeSizes, pub padding: EdgeSizes, pub border: EdgeSizes, pub children: Vec<LayoutBox>, pub font_size: f32, /// Positioned text fragments (populated for boxes with inline content). pub lines: Vec<TextLine>, /// Text color. pub color: Color, /// Background color. pub background_color: Color, /// Text decoration (underline, etc.). pub text_decoration: TextDecoration, /// Border styles (top, right, bottom, left). pub border_styles: [BorderStyle; 4], /// Border colors (top, right, bottom, left). pub border_colors: [Color; 4], /// Text alignment for this box's inline content. pub text_align: TextAlign, /// Computed line height in px. pub line_height: f32, /// For replaced elements (e.g., `<img>`): content dimensions (width, height). pub replaced_size: Option<(f32, f32)>, /// CSS `position` property. pub position: Position, /// Relative position offset (dx, dy) applied after normal flow layout. pub relative_offset: (f32, f32), /// CSS `overflow` property. pub overflow: Overflow,}
impl LayoutBox { fn new(box_type: BoxType, style: &ComputedStyle) -> Self { LayoutBox { box_type, rect: Rect::default(), margin: EdgeSizes::default(), padding: EdgeSizes::default(), border: EdgeSizes::default(), children: Vec::new(), font_size: style.font_size, lines: Vec::new(), color: style.color, background_color: style.background_color, text_decoration: style.text_decoration, border_styles: [ style.border_top_style, style.border_right_style, style.border_bottom_style, style.border_left_style, ], border_colors: [ style.border_top_color, style.border_right_color, style.border_bottom_color, style.border_left_color, ], text_align: style.text_align, line_height: style.line_height, replaced_size: None, position: style.position, relative_offset: (0.0, 0.0), overflow: style.overflow, } }
/// Total height including margin, border, and padding. pub fn margin_box_height(&self) -> f32 { self.margin.top + self.border.top + self.padding.top + self.rect.height + self.padding.bottom + self.border.bottom + self.margin.bottom }
/// Iterate over all boxes in depth-first pre-order. pub fn iter(&self) -> LayoutBoxIter<'_> { LayoutBoxIter { stack: vec![self] } }}
/// Depth-first pre-order iterator over layout boxes.pub struct LayoutBoxIter<'a> { stack: Vec<&'a LayoutBox>,}
impl<'a> Iterator for LayoutBoxIter<'a> { type Item = &'a LayoutBox;
fn next(&mut self) -> Option<&'a LayoutBox> { let node = self.stack.pop()?; for child in node.children.iter().rev() { self.stack.push(child); } Some(node) }}
/// The result of laying out a document.#[derive(Debug)]pub struct LayoutTree { pub root: LayoutBox, pub width: f32, pub height: f32,}
impl LayoutTree { /// Iterate over all layout boxes in depth-first pre-order. pub fn iter(&self) -> LayoutBoxIter<'_> { self.root.iter() }}
// ---------------------------------------------------------------------------// Resolve LengthOrAuto to f32// ---------------------------------------------------------------------------
fn resolve_length(value: LengthOrAuto) -> f32 { match value { LengthOrAuto::Length(px) => px, LengthOrAuto::Auto => 0.0, }}
/// Resolve horizontal offset for `position: relative`./// If both `left` and `right` are specified, `left` wins (CSS2 §9.4.3, ltr).fn resolve_relative_horizontal(left: LengthOrAuto, right: LengthOrAuto) -> f32 { match left { LengthOrAuto::Length(px) => px, LengthOrAuto::Auto => match right { LengthOrAuto::Length(px) => -px, LengthOrAuto::Auto => 0.0, }, }}
/// Resolve vertical offset for `position: relative`./// If both `top` and `bottom` are specified, `top` wins (CSS2 §9.4.3).fn resolve_relative_vertical(top: LengthOrAuto, bottom: LengthOrAuto) -> f32 { match top { LengthOrAuto::Length(px) => px, LengthOrAuto::Auto => match bottom { LengthOrAuto::Length(px) => -px, LengthOrAuto::Auto => 0.0, }, }}
// ---------------------------------------------------------------------------// Build layout tree from styled tree// ---------------------------------------------------------------------------
fn build_box( styled: &StyledNode, doc: &Document, image_sizes: &HashMap<NodeId, (f32, f32)>,) -> Option<LayoutBox> { let node = styled.node; let style = &styled.style;
match doc.node_data(node) { NodeData::Document => { let mut children = Vec::new(); for child in &styled.children { if let Some(child_box) = build_box(child, doc, image_sizes) { children.push(child_box); } } if children.len() == 1 { children.into_iter().next() } else if children.is_empty() { None } else { let mut b = LayoutBox::new(BoxType::Anonymous, style); b.children = children; Some(b) } } NodeData::Element { .. } => { if style.display == Display::None { return None; }
let margin = EdgeSizes { top: resolve_length(style.margin_top), right: resolve_length(style.margin_right), bottom: resolve_length(style.margin_bottom), left: resolve_length(style.margin_left), }; let padding = EdgeSizes { top: style.padding_top, right: style.padding_right, bottom: style.padding_bottom, left: style.padding_left, }; let border = EdgeSizes { top: if style.border_top_style != BorderStyle::None { style.border_top_width } else { 0.0 }, right: if style.border_right_style != BorderStyle::None { style.border_right_width } else { 0.0 }, bottom: if style.border_bottom_style != BorderStyle::None { style.border_bottom_width } else { 0.0 }, left: if style.border_left_style != BorderStyle::None { style.border_left_width } else { 0.0 }, };
let mut children = Vec::new(); for child in &styled.children { if let Some(child_box) = build_box(child, doc, image_sizes) { children.push(child_box); } }
let box_type = match style.display { Display::Block => BoxType::Block(node), Display::Inline => BoxType::Inline(node), Display::None => unreachable!(), };
if style.display == Display::Block { children = normalize_children(children, style); }
let mut b = LayoutBox::new(box_type, style); b.margin = margin; b.padding = padding; b.border = border; b.children = children;
// Check for replaced element (e.g., <img>). if let Some(&(w, h)) = image_sizes.get(&node) { b.replaced_size = Some((w, h)); }
// Compute relative position offset. if style.position == Position::Relative { let dx = resolve_relative_horizontal(style.left, style.right); let dy = resolve_relative_vertical(style.top, style.bottom); b.relative_offset = (dx, dy); }
Some(b) } NodeData::Text { data } => { let collapsed = collapse_whitespace(data); if collapsed.is_empty() { return None; } Some(LayoutBox::new( BoxType::TextRun { node, text: collapsed, }, style, )) } NodeData::Comment { .. } => None, }}
/// Collapse runs of whitespace to a single space.fn collapse_whitespace(s: &str) -> String { let mut result = String::new(); let mut in_ws = false; for ch in s.chars() { if ch.is_whitespace() { if !in_ws { result.push(' '); } in_ws = true; } else { in_ws = false; result.push(ch); } } result}
/// If a block container has a mix of block-level and inline-level children,/// wrap consecutive inline runs in anonymous block boxes.fn normalize_children(children: Vec<LayoutBox>, parent_style: &ComputedStyle) -> Vec<LayoutBox> { if children.is_empty() { return children; }
let has_block = children.iter().any(is_block_level); if !has_block { return children; }
let has_inline = children.iter().any(|c| !is_block_level(c)); if !has_inline { return children; }
let mut result = Vec::new(); let mut inline_group: Vec<LayoutBox> = Vec::new();
for child in children { if is_block_level(&child) { if !inline_group.is_empty() { let mut anon = LayoutBox::new(BoxType::Anonymous, parent_style); anon.children = std::mem::take(&mut inline_group); result.push(anon); } result.push(child); } else { inline_group.push(child); } }
if !inline_group.is_empty() { let mut anon = LayoutBox::new(BoxType::Anonymous, parent_style); anon.children = inline_group; result.push(anon); }
result}
fn is_block_level(b: &LayoutBox) -> bool { matches!(b.box_type, BoxType::Block(_) | BoxType::Anonymous)}
// ---------------------------------------------------------------------------// Layout algorithm// ---------------------------------------------------------------------------
/// Position and size a layout box within `available_width` at position (`x`, `y`).fn compute_layout( b: &mut LayoutBox, x: f32, y: f32, available_width: f32, font: &Font, doc: &Document,) { let content_x = x + b.margin.left + b.border.left + b.padding.left; let content_y = y + b.margin.top + b.border.top + b.padding.top; let content_width = (available_width - b.margin.left - b.margin.right - b.border.left - b.border.right - b.padding.left - b.padding.right) .max(0.0);
b.rect.x = content_x; b.rect.y = content_y; b.rect.width = content_width;
// Replaced elements (e.g., <img>) have intrinsic dimensions. if let Some((rw, rh)) = b.replaced_size { // Use CSS width/height if specified, otherwise use replaced dimensions. // Content width is the minimum of replaced width and available width. b.rect.width = rw.min(content_width); b.rect.height = rh; apply_relative_offset(b); return; }
match &b.box_type { BoxType::Block(_) | BoxType::Anonymous => { if has_block_children(b) { layout_block_children(b, font, doc); } else { layout_inline_children(b, font, doc); } } BoxType::TextRun { .. } | BoxType::Inline(_) => { // Handled by the parent's inline layout. } }
apply_relative_offset(b);}
/// Apply `position: relative` offset to a box and all its descendants.////// This shifts the visual position without affecting the normal-flow layout/// of surrounding elements (the original space is preserved).fn apply_relative_offset(b: &mut LayoutBox) { let (dx, dy) = b.relative_offset; if dx == 0.0 && dy == 0.0 { return; } shift_box(b, dx, dy);}
/// Recursively shift a box and all its descendants by (dx, dy).fn shift_box(b: &mut LayoutBox, dx: f32, dy: f32) { b.rect.x += dx; b.rect.y += dy; for line in &mut b.lines { line.x += dx; line.y += dy; } for child in &mut b.children { shift_box(child, dx, dy); }}
fn has_block_children(b: &LayoutBox) -> bool { b.children.iter().any(is_block_level)}
/// Collapse two adjoining margins per CSS2 §8.3.1.////// Both non-negative → use the larger./// Both negative → use the more negative./// Mixed → sum the largest positive and most negative.fn collapse_margins(a: f32, b: f32) -> f32 { if a >= 0.0 && b >= 0.0 { a.max(b) } else if a < 0.0 && b < 0.0 { a.min(b) } else { a + b }}
/// Returns `true` if this box establishes a new block formatting context,/// which prevents its margins from collapsing with children.fn establishes_bfc(b: &LayoutBox) -> bool { b.overflow != Overflow::Visible}
/// Returns `true` if a block box has no in-flow content (empty block).fn is_empty_block(b: &LayoutBox) -> bool { b.children.is_empty() && b.lines.is_empty() && b.replaced_size.is_none()}
/// Pre-collapse parent-child margins (CSS2 §8.3.1).////// When a parent has no border/padding/BFC separating it from its first/last/// child, the child's margin collapses into the parent's margin. This must/// happen *before* positioning so the parent is placed using the collapsed/// value. The function walks bottom-up: children are pre-collapsed first, then/// their (possibly enlarged) margins are folded into the parent.fn pre_collapse_margins(b: &mut LayoutBox) { // Recurse into block children first (bottom-up). for child in &mut b.children { if is_block_level(child) { pre_collapse_margins(child); } }
if !matches!(b.box_type, BoxType::Block(_) | BoxType::Anonymous) { return; } if establishes_bfc(b) { return; } if !has_block_children(b) { return; }
// --- Top: collapse with first non-empty child --- if b.border.top == 0.0 && b.padding.top == 0.0 { if let Some(child_top) = first_block_top_margin(&b.children) { b.margin.top = collapse_margins(b.margin.top, child_top); } }
// --- Bottom: collapse with last non-empty child --- if b.border.bottom == 0.0 && b.padding.bottom == 0.0 { if let Some(child_bottom) = last_block_bottom_margin(&b.children) { b.margin.bottom = collapse_margins(b.margin.bottom, child_bottom); } }}
/// Top margin of the first non-empty block child (already pre-collapsed).fn first_block_top_margin(children: &[LayoutBox]) -> Option<f32> { for child in children { if is_block_level(child) { if is_empty_block(child) { continue; } return Some(child.margin.top); } } // All block children empty — fold all their collapsed margins. let mut m = 0.0f32; for child in children.iter().filter(|c| is_block_level(c)) { m = collapse_margins(m, collapse_margins(child.margin.top, child.margin.bottom)); } if m != 0.0 { Some(m) } else { None }}
/// Bottom margin of the last non-empty block child (already pre-collapsed).fn last_block_bottom_margin(children: &[LayoutBox]) -> Option<f32> { for child in children.iter().rev() { if is_block_level(child) { if is_empty_block(child) { continue; } return Some(child.margin.bottom); } } let mut m = 0.0f32; for child in children.iter().filter(|c| is_block_level(c)) { m = collapse_margins(m, collapse_margins(child.margin.top, child.margin.bottom)); } if m != 0.0 { Some(m) } else { None }}
/// Lay out block-level children with vertical margin collapsing (CSS2 §8.3.1).////// Handles adjacent-sibling collapsing, empty-block collapsing, and/// parent-child internal spacing (the parent's external margins were already/// updated by `pre_collapse_margins`).fn layout_block_children(parent: &mut LayoutBox, font: &Font, doc: &Document) { let content_x = parent.rect.x; let content_width = parent.rect.width; let mut cursor_y = parent.rect.y;
let parent_top_open = parent.border.top == 0.0 && parent.padding.top == 0.0 && !establishes_bfc(parent); let parent_bottom_open = parent.border.bottom == 0.0 && parent.padding.bottom == 0.0 && !establishes_bfc(parent);
// Pending bottom margin from the previous sibling. let mut pending_margin: Option<f32> = None; let child_count = parent.children.len();
for i in 0..child_count { let child_top_margin = parent.children[i].margin.top; let child_bottom_margin = parent.children[i].margin.bottom;
// --- Empty block: top+bottom margins self-collapse --- if is_empty_block(&parent.children[i]) { let self_collapsed = collapse_margins(child_top_margin, child_bottom_margin); pending_margin = Some(match pending_margin { Some(prev) => collapse_margins(prev, self_collapsed), None => self_collapsed, }); // Position at cursor_y with zero height. let child = &mut parent.children[i]; child.rect.x = content_x + child.border.left + child.padding.left; child.rect.y = cursor_y + child.border.top + child.padding.top; child.rect.width = (content_width - child.border.left - child.border.right - child.padding.left - child.padding.right) .max(0.0); child.rect.height = 0.0; continue; }
// --- Compute effective top spacing --- let collapsed_top = if let Some(prev_bottom) = pending_margin.take() { // Sibling collapsing: previous bottom vs this top. collapse_margins(prev_bottom, child_top_margin) } else if i == 0 && parent_top_open { // First child, parent top open: margin was already pulled into // parent by pre_collapse_margins — no internal spacing. 0.0 } else { child_top_margin };
// `compute_layout` adds `child.margin.top` internally, so compensate. let y_for_child = cursor_y + collapsed_top - child_top_margin; compute_layout( &mut parent.children[i], content_x, y_for_child, content_width, font, doc, );
let child = &parent.children[i]; // Use the normal-flow position (before relative offset) so that // `position: relative` does not affect sibling placement. let (_, rel_dy) = child.relative_offset; cursor_y = (child.rect.y - rel_dy) + child.rect.height + child.padding.bottom + child.border.bottom; pending_margin = Some(child_bottom_margin); }
// Trailing margin. if let Some(trailing) = pending_margin { if !parent_bottom_open { // Parent has border/padding at bottom — margin stays inside. cursor_y += trailing; } // If parent_bottom_open, the margin was already pulled into the // parent by pre_collapse_margins. }
parent.rect.height = cursor_y - parent.rect.y;}
// ---------------------------------------------------------------------------// Inline formatting context// ---------------------------------------------------------------------------
/// An inline item produced by flattening the inline tree.enum InlineItemKind { /// A word of text with associated styling. Word { text: String, font_size: f32, color: Color, text_decoration: TextDecoration, background_color: Color, }, /// Whitespace between words. Space { font_size: f32 }, /// Forced line break (`<br>`). ForcedBreak, /// Start of an inline box (for margin/padding/border tracking). InlineStart { margin_left: f32, padding_left: f32, border_left: f32, }, /// End of an inline box. InlineEnd { margin_right: f32, padding_right: f32, border_right: f32, },}
/// A pending fragment on the current line.struct PendingFragment { text: String, x: f32, width: f32, font_size: f32, color: Color, text_decoration: TextDecoration, background_color: Color,}
/// Flatten the inline children tree into a sequence of items.fn flatten_inline_tree(children: &[LayoutBox], doc: &Document, items: &mut Vec<InlineItemKind>) { for child in children { match &child.box_type { BoxType::TextRun { text, .. } => { let words = split_into_words(text); for segment in words { match segment { WordSegment::Word(w) => { items.push(InlineItemKind::Word { text: w, font_size: child.font_size, color: child.color, text_decoration: child.text_decoration, background_color: child.background_color, }); } WordSegment::Space => { items.push(InlineItemKind::Space { font_size: child.font_size, }); } } } } BoxType::Inline(node_id) => { if let NodeData::Element { tag_name, .. } = doc.node_data(*node_id) { if tag_name == "br" { items.push(InlineItemKind::ForcedBreak); continue; } }
items.push(InlineItemKind::InlineStart { margin_left: child.margin.left, padding_left: child.padding.left, border_left: child.border.left, });
flatten_inline_tree(&child.children, doc, items);
items.push(InlineItemKind::InlineEnd { margin_right: child.margin.right, padding_right: child.padding.right, border_right: child.border.right, }); } _ => {} } }}
enum WordSegment { Word(String), Space,}
/// Split text into alternating words and spaces.fn split_into_words(text: &str) -> Vec<WordSegment> { let mut segments = Vec::new(); let mut current_word = String::new();
for ch in text.chars() { if ch == ' ' { if !current_word.is_empty() { segments.push(WordSegment::Word(std::mem::take(&mut current_word))); } segments.push(WordSegment::Space); } else { current_word.push(ch); } }
if !current_word.is_empty() { segments.push(WordSegment::Word(current_word)); }
segments}
/// Lay out inline children using a proper inline formatting context.fn layout_inline_children(parent: &mut LayoutBox, font: &Font, doc: &Document) { let available_width = parent.rect.width; let text_align = parent.text_align; let line_height = parent.line_height;
let mut items = Vec::new(); flatten_inline_tree(&parent.children, doc, &mut items);
if items.is_empty() { parent.rect.height = 0.0; return; }
// Process items into line boxes. let mut all_lines: Vec<Vec<PendingFragment>> = Vec::new(); let mut current_line: Vec<PendingFragment> = Vec::new(); let mut cursor_x: f32 = 0.0;
for item in &items { match item { InlineItemKind::Word { text, font_size, color, text_decoration, background_color, } => { let word_width = measure_text_width(font, text, *font_size);
// If this word doesn't fit and the line isn't empty, break. if cursor_x > 0.0 && cursor_x + word_width > available_width { all_lines.push(std::mem::take(&mut current_line)); cursor_x = 0.0; }
current_line.push(PendingFragment { text: text.clone(), x: cursor_x, width: word_width, font_size: *font_size, color: *color, text_decoration: *text_decoration, background_color: *background_color, }); cursor_x += word_width; } InlineItemKind::Space { font_size } => { // Only add space if we have content on the line. if !current_line.is_empty() { let space_width = measure_text_width(font, " ", *font_size); if cursor_x + space_width <= available_width { cursor_x += space_width; } } } InlineItemKind::ForcedBreak => { all_lines.push(std::mem::take(&mut current_line)); cursor_x = 0.0; } InlineItemKind::InlineStart { margin_left, padding_left, border_left, } => { cursor_x += margin_left + padding_left + border_left; } InlineItemKind::InlineEnd { margin_right, padding_right, border_right, } => { cursor_x += margin_right + padding_right + border_right; } } }
// Flush the last line. if !current_line.is_empty() { all_lines.push(current_line); }
if all_lines.is_empty() { parent.rect.height = 0.0; return; }
// Position lines vertically and apply text-align. let mut text_lines = Vec::new(); let mut y = parent.rect.y; let num_lines = all_lines.len();
for (line_idx, line_fragments) in all_lines.iter().enumerate() { if line_fragments.is_empty() { y += line_height; continue; }
// Compute line width from last fragment. let line_width = match line_fragments.last() { Some(last) => last.x + last.width, None => 0.0, };
// Compute text-align offset. let is_last_line = line_idx == num_lines - 1; let align_offset = compute_align_offset(text_align, available_width, line_width, is_last_line);
for frag in line_fragments { text_lines.push(TextLine { text: frag.text.clone(), x: parent.rect.x + frag.x + align_offset, y, width: frag.width, font_size: frag.font_size, color: frag.color, text_decoration: frag.text_decoration, background_color: frag.background_color, }); }
y += line_height; }
parent.rect.height = num_lines as f32 * line_height; parent.lines = text_lines;}
/// Compute the horizontal offset for text alignment.fn compute_align_offset( align: TextAlign, available_width: f32, line_width: f32, is_last_line: bool,) -> f32 { let extra_space = (available_width - line_width).max(0.0); match align { TextAlign::Left => 0.0, TextAlign::Center => extra_space / 2.0, TextAlign::Right => extra_space, TextAlign::Justify => { // Don't justify the last line (CSS spec behavior). if is_last_line { 0.0 } else { // For justify, we shift the whole line by 0 — the actual distribution // of space between words would need per-word spacing. For now, treat // as left-aligned; full justify support is a future enhancement. 0.0 } } }}
// ---------------------------------------------------------------------------// Text measurement// ---------------------------------------------------------------------------
/// Measure the total advance width of a text string at the given font size.fn measure_text_width(font: &Font, text: &str, font_size: f32) -> f32 { let shaped = font.shape_text(text, font_size); match shaped.last() { Some(last) => last.x_offset + last.x_advance, None => 0.0, }}
// ---------------------------------------------------------------------------// Public API// ---------------------------------------------------------------------------
/// Build and lay out from a styled tree (produced by `resolve_styles`).////// Returns a `LayoutTree` with positioned boxes ready for rendering.pub fn layout( styled_root: &StyledNode, doc: &Document, viewport_width: f32, _viewport_height: f32, font: &Font, image_sizes: &HashMap<NodeId, (f32, f32)>,) -> LayoutTree { let mut root = match build_box(styled_root, doc, image_sizes) { Some(b) => b, None => { return LayoutTree { root: LayoutBox::new(BoxType::Anonymous, &ComputedStyle::default()), width: viewport_width, height: 0.0, }; } };
// Pre-collapse parent-child margins before positioning. pre_collapse_margins(&mut root);
compute_layout(&mut root, 0.0, 0.0, viewport_width, font, doc);
let height = root.margin_box_height(); LayoutTree { root, width: viewport_width, height, }}
#[cfg(test)]mod tests { use super::*; use we_dom::Document; use we_style::computed::{extract_stylesheets, resolve_styles};
fn test_font() -> Font { let paths = [ "/System/Library/Fonts/Geneva.ttf", "/System/Library/Fonts/Monaco.ttf", ]; for path in &paths { let p = std::path::Path::new(path); if p.exists() { return Font::from_file(p).expect("failed to parse font"); } } panic!("no test font found"); }
fn layout_doc(doc: &Document) -> LayoutTree { let font = test_font(); let sheets = extract_stylesheets(doc); let styled = resolve_styles(doc, &sheets).unwrap(); layout(&styled, doc, 800.0, 600.0, &font, &HashMap::new()) }
#[test] fn empty_document() { let doc = Document::new(); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets); if let Some(styled) = styled { let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new()); assert_eq!(tree.width, 800.0); } }
#[test] fn single_paragraph() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); let p = doc.create_element("p"); let text = doc.create_text("Hello world"); doc.append_child(root, html); doc.append_child(html, body); doc.append_child(body, p); doc.append_child(p, text);
let tree = layout_doc(&doc);
assert!(matches!(tree.root.box_type, BoxType::Block(_)));
let body_box = &tree.root.children[0]; assert!(matches!(body_box.box_type, BoxType::Block(_)));
let p_box = &body_box.children[0]; assert!(matches!(p_box.box_type, BoxType::Block(_)));
assert!(!p_box.lines.is_empty(), "p should have text fragments");
// Collect all text on the first visual line. let first_y = p_box.lines[0].y; let line_text: String = p_box .lines .iter() .filter(|l| (l.y - first_y).abs() < 0.01) .map(|l| l.text.as_str()) .collect::<Vec<_>>() .join(" "); assert!( line_text.contains("Hello") && line_text.contains("world"), "line should contain Hello and world, got: {line_text}" );
assert_eq!(p_box.margin.top, 16.0); assert_eq!(p_box.margin.bottom, 16.0); }
#[test] fn blocks_stack_vertically() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); let p1 = doc.create_element("p"); let t1 = doc.create_text("First"); let p2 = doc.create_element("p"); let t2 = doc.create_text("Second"); doc.append_child(root, html); doc.append_child(html, body); doc.append_child(body, p1); doc.append_child(p1, t1); doc.append_child(body, p2); doc.append_child(p2, t2);
let tree = layout_doc(&doc); let body_box = &tree.root.children[0]; let first = &body_box.children[0]; let second = &body_box.children[1];
assert!( second.rect.y > first.rect.y, "second p (y={}) should be below first p (y={})", second.rect.y, first.rect.y ); }
#[test] fn heading_larger_than_body() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); let h1 = doc.create_element("h1"); let h1_text = doc.create_text("Title"); let p = doc.create_element("p"); let p_text = doc.create_text("Text"); doc.append_child(root, html); doc.append_child(html, body); doc.append_child(body, h1); doc.append_child(h1, h1_text); doc.append_child(body, p); doc.append_child(p, p_text);
let tree = layout_doc(&doc); let body_box = &tree.root.children[0]; let h1_box = &body_box.children[0]; let p_box = &body_box.children[1];
assert!( h1_box.font_size > p_box.font_size, "h1 font_size ({}) should be > p font_size ({})", h1_box.font_size, p_box.font_size ); assert_eq!(h1_box.font_size, 32.0);
assert!( h1_box.rect.height > p_box.rect.height, "h1 height ({}) should be > p height ({})", h1_box.rect.height, p_box.rect.height ); }
#[test] fn body_has_default_margin() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); let p = doc.create_element("p"); let text = doc.create_text("Test"); doc.append_child(root, html); doc.append_child(html, body); doc.append_child(body, p); doc.append_child(p, text);
let tree = layout_doc(&doc); let body_box = &tree.root.children[0];
// body default margin is 8px, but it collapses with p's 16px margin // (parent-child collapsing: no border/padding on body). assert_eq!(body_box.margin.top, 16.0); assert_eq!(body_box.margin.right, 8.0); assert_eq!(body_box.margin.bottom, 16.0); assert_eq!(body_box.margin.left, 8.0);
assert_eq!(body_box.rect.x, 8.0); // body.rect.y = collapsed margin (16) from viewport top. assert_eq!(body_box.rect.y, 16.0); }
#[test] fn text_wraps_at_container_width() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); let p = doc.create_element("p"); let text = doc.create_text("The quick brown fox jumps over the lazy dog and more words to wrap"); doc.append_child(root, html); doc.append_child(html, body); doc.append_child(body, p); doc.append_child(p, text);
let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 100.0, 600.0, &font, &HashMap::new()); let body_box = &tree.root.children[0]; let p_box = &body_box.children[0];
// Count distinct y-positions to count visual lines. let mut ys: Vec<f32> = p_box.lines.iter().map(|l| l.y).collect(); ys.sort_by(|a, b| a.partial_cmp(b).unwrap()); ys.dedup_by(|a, b| (*a - *b).abs() < 0.01);
assert!( ys.len() > 1, "text should wrap to multiple lines, got {} visual lines", ys.len() ); }
#[test] fn layout_produces_positive_dimensions() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); let div = doc.create_element("div"); let text = doc.create_text("Content"); doc.append_child(root, html); doc.append_child(html, body); doc.append_child(body, div); doc.append_child(div, text);
let tree = layout_doc(&doc);
for b in tree.iter() { assert!(b.rect.width >= 0.0, "width should be >= 0"); assert!(b.rect.height >= 0.0, "height should be >= 0"); }
assert!(tree.height > 0.0, "layout height should be > 0"); }
#[test] fn head_is_hidden() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let head = doc.create_element("head"); let title = doc.create_element("title"); let title_text = doc.create_text("Page Title"); let body = doc.create_element("body"); let p = doc.create_element("p"); let p_text = doc.create_text("Visible"); doc.append_child(root, html); doc.append_child(html, head); doc.append_child(head, title); doc.append_child(title, title_text); doc.append_child(html, body); doc.append_child(body, p); doc.append_child(p, p_text);
let tree = layout_doc(&doc);
assert_eq!( tree.root.children.len(), 1, "html should have 1 child (body), head should be hidden" ); }
#[test] fn mixed_block_and_inline() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); let div = doc.create_element("div"); let text1 = doc.create_text("Text"); let p = doc.create_element("p"); let p_text = doc.create_text("Block"); let text2 = doc.create_text("More"); doc.append_child(root, html); doc.append_child(html, body); doc.append_child(body, div); doc.append_child(div, text1); doc.append_child(div, p); doc.append_child(p, p_text); doc.append_child(div, text2);
let tree = layout_doc(&doc); let body_box = &tree.root.children[0]; let div_box = &body_box.children[0];
assert_eq!( div_box.children.len(), 3, "div should have 3 children (anon, block, anon), got {}", div_box.children.len() );
assert!(matches!(div_box.children[0].box_type, BoxType::Anonymous)); assert!(matches!(div_box.children[1].box_type, BoxType::Block(_))); assert!(matches!(div_box.children[2].box_type, BoxType::Anonymous)); }
#[test] fn inline_elements_contribute_text() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); let p = doc.create_element("p"); let t1 = doc.create_text("Hello "); let em = doc.create_element("em"); let t2 = doc.create_text("world"); let t3 = doc.create_text("!"); doc.append_child(root, html); doc.append_child(html, body); doc.append_child(body, p); doc.append_child(p, t1); doc.append_child(p, em); doc.append_child(em, t2); doc.append_child(p, t3);
let tree = layout_doc(&doc); let body_box = &tree.root.children[0]; let p_box = &body_box.children[0];
assert!(!p_box.lines.is_empty());
let first_y = p_box.lines[0].y; let line_texts: Vec<&str> = p_box .lines .iter() .filter(|l| (l.y - first_y).abs() < 0.01) .map(|l| l.text.as_str()) .collect(); let combined = line_texts.join(""); assert!( combined.contains("Hello") && combined.contains("world") && combined.contains("!"), "line should contain all text, got: {combined}" ); }
#[test] fn collapse_whitespace_works() { assert_eq!(collapse_whitespace("hello world"), "hello world"); assert_eq!(collapse_whitespace(" spaces "), " spaces "); assert_eq!(collapse_whitespace("\n\ttabs\n"), " tabs "); assert_eq!(collapse_whitespace("no-extra"), "no-extra"); assert_eq!(collapse_whitespace(" "), " "); }
#[test] fn content_width_respects_body_margin() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); let div = doc.create_element("div"); let text = doc.create_text("Content"); doc.append_child(root, html); doc.append_child(html, body); doc.append_child(body, div); doc.append_child(div, text);
let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new()); let body_box = &tree.root.children[0];
assert_eq!(body_box.rect.width, 784.0);
let div_box = &body_box.children[0]; assert_eq!(div_box.rect.width, 784.0); }
#[test] fn multiple_heading_levels() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); doc.append_child(root, html); doc.append_child(html, body);
let tags = ["h1", "h2", "h3"]; for tag in &tags { let h = doc.create_element(tag); let t = doc.create_text(tag); doc.append_child(body, h); doc.append_child(h, t); }
let tree = layout_doc(&doc); let body_box = &tree.root.children[0];
let h1 = &body_box.children[0]; let h2 = &body_box.children[1]; let h3 = &body_box.children[2]; assert!(h1.font_size > h2.font_size); assert!(h2.font_size > h3.font_size);
assert!(h2.rect.y > h1.rect.y); assert!(h3.rect.y > h2.rect.y); }
#[test] fn layout_tree_iteration() { let mut doc = Document::new(); let root = doc.root(); let html = doc.create_element("html"); let body = doc.create_element("body"); let p = doc.create_element("p"); let text = doc.create_text("Test"); doc.append_child(root, html); doc.append_child(html, body); doc.append_child(body, p); doc.append_child(p, text);
let tree = layout_doc(&doc); let count = tree.iter().count(); assert!(count >= 3, "should have at least html, body, p boxes"); }
#[test] fn css_style_affects_layout() { let html_str = r#"<!DOCTYPE html><html><head><style>p { margin-top: 50px; margin-bottom: 50px; }</style></head><body><p>First</p><p>Second</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let first = &body_box.children[0]; let second = &body_box.children[1];
assert_eq!(first.margin.top, 50.0); assert_eq!(first.margin.bottom, 50.0);
// Adjacent sibling margins collapse: gap = max(50, 50) = 50, not 100. let gap = second.rect.y - (first.rect.y + first.rect.height); assert!( (gap - 50.0).abs() < 1.0, "collapsed margin gap should be ~50px, got {gap}" ); }
#[test] fn inline_style_affects_layout() { let html_str = r#"<!DOCTYPE html><html><body><div style="padding-top: 20px; padding-bottom: 20px;"><p>Content</p></div></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let div_box = &body_box.children[0];
assert_eq!(div_box.padding.top, 20.0); assert_eq!(div_box.padding.bottom, 20.0); }
#[test] fn css_color_propagates_to_layout() { let html_str = r#"<!DOCTYPE html><html><head><style>p { color: red; background-color: blue; }</style></head><body><p>Colored</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let p_box = &body_box.children[0];
assert_eq!(p_box.color, Color::rgb(255, 0, 0)); assert_eq!(p_box.background_color, Color::rgb(0, 0, 255)); }
// --- New inline layout tests ---
#[test] fn inline_elements_have_per_fragment_styling() { let html_str = r#"<!DOCTYPE html><html><head><style>em { color: red; }</style></head><body><p>Hello <em>world</em></p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let p_box = &body_box.children[0];
let colors: Vec<Color> = p_box.lines.iter().map(|l| l.color).collect(); assert!( colors.iter().any(|c| *c == Color::rgb(0, 0, 0)), "should have black text" ); assert!( colors.iter().any(|c| *c == Color::rgb(255, 0, 0)), "should have red text from <em>" ); }
#[test] fn br_element_forces_line_break() { let html_str = r#"<!DOCTYPE html><html><body><p>Line one<br>Line two</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let p_box = &body_box.children[0];
let mut ys: Vec<f32> = p_box.lines.iter().map(|l| l.y).collect(); ys.sort_by(|a, b| a.partial_cmp(b).unwrap()); ys.dedup_by(|a, b| (*a - *b).abs() < 0.01);
assert!( ys.len() >= 2, "<br> should produce 2 visual lines, got {}", ys.len() ); }
#[test] fn text_align_center() { let html_str = r#"<!DOCTYPE html><html><head><style>p { text-align: center; }</style></head><body><p>Hi</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let p_box = &body_box.children[0];
assert!(!p_box.lines.is_empty()); let first = &p_box.lines[0]; // Center-aligned: text should be noticeably offset from content x. assert!( first.x > p_box.rect.x + 10.0, "center-aligned text x ({}) should be offset from content x ({})", first.x, p_box.rect.x ); }
#[test] fn text_align_right() { let html_str = r#"<!DOCTYPE html><html><head><style>p { text-align: right; }</style></head><body><p>Hi</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let p_box = &body_box.children[0];
assert!(!p_box.lines.is_empty()); let first = &p_box.lines[0]; let right_edge = p_box.rect.x + p_box.rect.width; assert!( (first.x + first.width - right_edge).abs() < 1.0, "right-aligned text end ({}) should be near right edge ({})", first.x + first.width, right_edge ); }
#[test] fn inline_padding_offsets_text() { let html_str = r#"<!DOCTYPE html><html><head><style>span { padding-left: 20px; padding-right: 20px; }</style></head><body><p>A<span>B</span>C</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let p_box = &body_box.children[0];
// Should have at least 3 fragments: A, B, C assert!( p_box.lines.len() >= 3, "should have fragments for A, B, C, got {}", p_box.lines.len() );
// B should be offset by the span's padding. let a_frag = &p_box.lines[0]; let b_frag = &p_box.lines[1]; let gap = b_frag.x - (a_frag.x + a_frag.width); // Gap should include the 20px padding-left from the span. assert!( gap >= 19.0, "gap between A and B ({gap}) should include span padding-left (20px)" ); }
#[test] fn text_fragments_have_correct_font_size() { let html_str = r#"<!DOCTYPE html><html><body><h1>Big</h1><p>Small</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let h1_box = &body_box.children[0]; let p_box = &body_box.children[1];
assert!(!h1_box.lines.is_empty()); assert!(!p_box.lines.is_empty()); assert_eq!(h1_box.lines[0].font_size, 32.0); assert_eq!(p_box.lines[0].font_size, 16.0); }
#[test] fn line_height_from_computed_style() { let html_str = r#"<!DOCTYPE html><html><head><style>p { line-height: 30px; }</style></head><body><p>Line one Line two Line three</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); // Narrow viewport to force wrapping. let tree = layout(&styled, &doc, 100.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let p_box = &body_box.children[0];
let mut ys: Vec<f32> = p_box.lines.iter().map(|l| l.y).collect(); ys.sort_by(|a, b| a.partial_cmp(b).unwrap()); ys.dedup_by(|a, b| (*a - *b).abs() < 0.01);
if ys.len() >= 2 { let gap = ys[1] - ys[0]; assert!( (gap - 30.0).abs() < 1.0, "line spacing ({gap}) should be ~30px from line-height" ); } }
// --- Relative positioning tests ---
#[test] fn relative_position_top_left() { let html_str = r#"<!DOCTYPE html><html><body><div style="position: relative; top: 10px; left: 20px;">Content</div></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let div_box = &body_box.children[0];
assert_eq!(div_box.position, Position::Relative); assert_eq!(div_box.relative_offset, (20.0, 10.0));
// The div should be shifted from where it would be in normal flow. // Normal flow position: body.rect.x + margin, body.rect.y + margin. // With relative offset: shifted by (20, 10). // Body has 8px margin by default, so content starts at x=8, y=8. assert!( (div_box.rect.x - (8.0 + 20.0)).abs() < 0.01, "div x ({}) should be 28.0 (8 + 20)", div_box.rect.x ); assert!( (div_box.rect.y - (8.0 + 10.0)).abs() < 0.01, "div y ({}) should be 18.0 (8 + 10)", div_box.rect.y ); }
#[test] fn relative_position_does_not_affect_siblings() { let html_str = r#"<!DOCTYPE html><html><head><style>p { margin: 0; }</style></head><body><p id="first" style="position: relative; top: 50px;">First</p><p id="second">Second</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let first = &body_box.children[0]; let second = &body_box.children[1];
// The first paragraph is shifted down by 50px visually. assert_eq!(first.relative_offset, (0.0, 50.0));
// But the second paragraph should be at its normal-flow position, // as if the first paragraph were NOT shifted. The second paragraph // should come right after the first's normal-flow height. // Body content starts at y=8 (default body margin). First p has 0 margin. // Second p should start right after first p's height (without offset). let first_normal_y = 8.0; // body margin let first_height = first.rect.height; let expected_second_y = first_normal_y + first_height; assert!( (second.rect.y - expected_second_y).abs() < 1.0, "second y ({}) should be at normal-flow position ({expected_second_y}), not affected by first's relative offset", second.rect.y ); }
#[test] fn relative_position_conflicting_offsets() { // When both top and bottom are specified, top wins. // When both left and right are specified, left wins. let html_str = r#"<!DOCTYPE html><html><body><div style="position: relative; top: 10px; bottom: 20px; left: 30px; right: 40px;">Content</div></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let div_box = &body_box.children[0];
// top wins over bottom: dy = 10 (not -20) // left wins over right: dx = 30 (not -40) assert_eq!(div_box.relative_offset, (30.0, 10.0)); }
#[test] fn relative_position_auto_offsets() { // auto offsets should resolve to 0 (no movement). let html_str = r#"<!DOCTYPE html><html><body><div style="position: relative;">Content</div></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let div_box = &body_box.children[0];
assert_eq!(div_box.position, Position::Relative); assert_eq!(div_box.relative_offset, (0.0, 0.0)); }
#[test] fn relative_position_bottom_right() { // bottom: 15px should shift up by 15px (negative direction). // right: 25px should shift left by 25px (negative direction). let html_str = r#"<!DOCTYPE html><html><body><div style="position: relative; bottom: 15px; right: 25px;">Content</div></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let div_box = &body_box.children[0];
assert_eq!(div_box.relative_offset, (-25.0, -15.0)); }
#[test] fn relative_position_shifts_text_lines() { let html_str = r#"<!DOCTYPE html><html><head><style>p { margin: 0; }</style></head><body><p style="position: relative; top: 30px; left: 40px;">Hello</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let p_box = &body_box.children[0];
assert!(!p_box.lines.is_empty(), "p should have text lines"); let first_line = &p_box.lines[0];
// Text should be shifted by the relative offset. // Body content starts at x=8, y=8. With offset: x=48, y=38. assert!( first_line.x >= 8.0 + 40.0 - 1.0, "text x ({}) should be shifted by left offset", first_line.x ); assert!( first_line.y >= 8.0 + 30.0 - 1.0, "text y ({}) should be shifted by top offset", first_line.y ); }
#[test] fn static_position_has_no_offset() { let html_str = r#"<!DOCTYPE html><html><body><div>Normal flow</div></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let div_box = &body_box.children[0];
assert_eq!(div_box.position, Position::Static); assert_eq!(div_box.relative_offset, (0.0, 0.0)); }
// --- Margin collapsing tests ---
#[test] fn adjacent_sibling_margins_collapse() { // Two <p> elements each with margin 16px: gap should be 16px (max), not 32px (sum). let html_str = r#"<!DOCTYPE html><html><head><style>body { margin: 0; border-top: 1px solid black; }p { margin-top: 16px; margin-bottom: 16px; }</style></head><body><p>First</p><p>Second</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let first = &body_box.children[0]; let second = &body_box.children[1];
// Gap between first's bottom border-box and second's top border-box // should be the collapsed margin: max(16, 16) = 16. let first_bottom = first.rect.y + first.rect.height + first.padding.bottom + first.border.bottom; let gap = second.rect.y - second.border.top - second.padding.top - first_bottom; assert!( (gap - 16.0).abs() < 1.0, "collapsed sibling margin should be ~16px, got {gap}" ); }
#[test] fn sibling_margins_collapse_unequal() { // p1 bottom-margin 20, p2 top-margin 30: gap should be 30 (max). let html_str = r#"<!DOCTYPE html><html><head><style>body { margin: 0; border-top: 1px solid black; }.first { margin-top: 0; margin-bottom: 20px; }.second { margin-top: 30px; margin-bottom: 0; }</style></head><body><p class="first">First</p><p class="second">Second</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let first = &body_box.children[0]; let second = &body_box.children[1];
let first_bottom = first.rect.y + first.rect.height + first.padding.bottom + first.border.bottom; let gap = second.rect.y - second.border.top - second.padding.top - first_bottom; assert!( (gap - 30.0).abs() < 1.0, "collapsed margin should be max(20, 30) = 30, got {gap}" ); }
#[test] fn parent_first_child_margin_collapsing() { // Parent with no padding/border: first child's top margin collapses. let html_str = r#"<!DOCTYPE html><html><head><style>body { margin: 0; border-top: 1px solid black; }.parent { margin-top: 10px; }.child { margin-top: 20px; }</style></head><body><div class="parent"><p class="child">Child</p></div></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let parent_box = &body_box.children[0];
// Parent margin collapses with child's: max(10, 20) = 20. assert_eq!(parent_box.margin.top, 20.0); }
#[test] fn negative_margin_collapsing() { // One positive (20) and one negative (-10): collapsed = 20 + (-10) = 10. let html_str = r#"<!DOCTYPE html><html><head><style>body { margin: 0; border-top: 1px solid black; }.first { margin-top: 0; margin-bottom: 20px; }.second { margin-top: -10px; margin-bottom: 0; }</style></head><body><p class="first">First</p><p class="second">Second</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let first = &body_box.children[0]; let second = &body_box.children[1];
let first_bottom = first.rect.y + first.rect.height + first.padding.bottom + first.border.bottom; let gap = second.rect.y - second.border.top - second.padding.top - first_bottom; // 20 + (-10) = 10 assert!( (gap - 10.0).abs() < 1.0, "positive + negative margin collapse should be 10, got {gap}" ); }
#[test] fn both_negative_margins_collapse() { // Both negative: use the more negative value. let html_str = r#"<!DOCTYPE html><html><head><style>body { margin: 0; border-top: 1px solid black; }.first { margin-top: 0; margin-bottom: -10px; }.second { margin-top: -20px; margin-bottom: 0; }</style></head><body><p class="first">First</p><p class="second">Second</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let first = &body_box.children[0]; let second = &body_box.children[1];
let first_bottom = first.rect.y + first.rect.height + first.padding.bottom + first.border.bottom; let gap = second.rect.y - second.border.top - second.padding.top - first_bottom; // Both negative: min(-10, -20) = -20 assert!( (gap - (-20.0)).abs() < 1.0, "both-negative margin collapse should be -20, got {gap}" ); }
#[test] fn border_blocks_margin_collapsing() { // When border separates margins, they don't collapse. let html_str = r#"<!DOCTYPE html><html><head><style>body { margin: 0; border-top: 1px solid black; }.first { margin-top: 0; margin-bottom: 20px; border-bottom: 1px solid black; }.second { margin-top: 20px; border-top: 1px solid black; }</style></head><body><p class="first">First</p><p class="second">Second</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let first = &body_box.children[0]; let second = &body_box.children[1];
// Borders are on the elements themselves, but the MARGINS are still // between the border boxes — sibling margins still collapse regardless // of borders on the elements. The margin gap = max(20, 20) = 20. let first_bottom = first.rect.y + first.rect.height + first.padding.bottom + first.border.bottom; let gap = second.rect.y - second.border.top - second.padding.top - first_bottom; assert!( (gap - 20.0).abs() < 1.0, "sibling margins collapse even with borders on elements, gap should be 20, got {gap}" ); }
#[test] fn padding_blocks_parent_child_collapsing() { // Parent with padding-top prevents margin collapsing with first child. let html_str = r#"<!DOCTYPE html><html><head><style>body { margin: 0; border-top: 1px solid black; }.parent { margin-top: 10px; padding-top: 5px; }.child { margin-top: 20px; }</style></head><body><div class="parent"><p class="child">Child</p></div></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let parent_box = &body_box.children[0];
// Parent has padding-top, so no collapsing: margin stays at 10. assert_eq!(parent_box.margin.top, 10.0); }
#[test] fn empty_block_margins_collapse() { // An empty div's top and bottom margins collapse with adjacent margins. let html_str = r#"<!DOCTYPE html><html><head><style>body { margin: 0; border-top: 1px solid black; }.spacer { margin-top: 10px; margin-bottom: 10px; }p { margin-top: 5px; margin-bottom: 5px; }</style></head><body><p>Before</p><div class="spacer"></div><p>After</p></body></html>"#; let doc = we_html::parse_html(html_str); let font = test_font(); let sheets = extract_stylesheets(&doc); let styled = resolve_styles(&doc, &sheets).unwrap(); let tree = layout(&styled, &doc, 800.0, 600.0, &font, &HashMap::new());
let body_box = &tree.root.children[0]; let before = &body_box.children[0]; let after = &body_box.children[2]; // [0]=p, [1]=empty div, [2]=p
// Empty div's margins (10+10) self-collapse to max(10,10)=10. // Then collapse with before's bottom (5) and after's top (5): // collapse(5, collapse(10, 10)) = collapse(5, 10) = 10 // Then collapse(10, 5) = 10. // So total gap between before and after = 10. let before_bottom = before.rect.y + before.rect.height + before.padding.bottom + before.border.bottom; let gap = after.rect.y - after.border.top - after.padding.top - before_bottom; assert!( (gap - 10.0).abs() < 1.0, "empty block margin collapse gap should be ~10px, got {gap}" ); }
#[test] fn collapse_margins_unit() { // Unit tests for the collapse_margins helper. assert_eq!(collapse_margins(10.0, 20.0), 20.0); assert_eq!(collapse_margins(20.0, 10.0), 20.0); assert_eq!(collapse_margins(0.0, 15.0), 15.0); assert_eq!(collapse_margins(-5.0, -10.0), -10.0); assert_eq!(collapse_margins(20.0, -5.0), 15.0); assert_eq!(collapse_margins(-5.0, 20.0), 15.0); assert_eq!(collapse_margins(0.0, 0.0), 0.0); }}