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https://github.com/SerenityOS/serenity
synced 2024-09-06 08:56:40 +00:00
LibWeb: Use more precise font metrics when doing inline layout
We now position inline-level boxes based on ascent and descent metrics from the font in use. This makes our basic text layouts look a lot more like those produced by other browsers. :^) I've tried to match the terminology used by the CSS Inline Layout spec. This will regress Acid2 a little bit, and probably various other sites, but on the whole it's the direction we should be heading, so let's go.
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@ -274,7 +274,7 @@ void InlineFormattingContext::generate_line_boxes(LayoutMode layout_mode)
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item.margin_start,
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item.margin_end,
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item.width,
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text_node.computed_values().font_size());
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text_node.line_height());
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break;
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}
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}
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@ -139,49 +139,4 @@ Gfx::FloatRect LineBoxFragment::selection_rect(const Gfx::Font& font) const
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return {};
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}
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float LineBoxFragment::height_of_inline_level_box(FormattingState const& state) const
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{
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auto height = [&] {
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// From "10.8 Line height calculations: the 'line-height' and 'vertical-align' properties"
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// https://www.w3.org/TR/CSS22/visudet.html#line-height
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// For replaced elements, inline-block elements, and inline-table elements, this is the height of their margin box.
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// FIXME: Support inline-table elements.
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if (layout_node().is_replaced_box() || layout_node().is_inline_block()) {
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auto const& fragment_box_state = state.get(static_cast<Box const&>(layout_node()));
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return fragment_box_state.margin_box_height();
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}
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// For inline boxes, this is their 'line-height'.
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return layout_node().line_height();
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}();
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if (auto length_percentage = layout_node().computed_values().vertical_align().get_pointer<CSS::LengthPercentage>(); length_percentage && length_percentage->is_length())
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height += length_percentage->length().to_px(layout_node());
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return height;
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}
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float LineBoxFragment::top_of_inline_level_box(FormattingState const& state) const
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{
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// FIXME: Support inline-table elements.
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if (layout_node().is_replaced_box() || layout_node().is_inline_block()) {
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auto const& fragment_box_state = state.get(static_cast<Box const&>(layout_node()));
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return m_offset.y() - fragment_box_state.margin_box_top();
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}
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return m_offset.y() - (layout_node().line_height() - layout_node().computed_values().font_size()) / 2;
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}
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float LineBoxFragment::bottom_of_inline_level_box(FormattingState const& state) const
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{
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auto bottom = [&] {
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// FIXME: Support inline-table elements.
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if (layout_node().is_replaced_box() || layout_node().is_inline_block()) {
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auto const& fragment_box_state = state.get(static_cast<Box const&>(layout_node()));
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return m_offset.y() + fragment_box_state.content_height + fragment_box_state.margin_box_bottom();
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}
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return m_offset.y() + (layout_node().line_height() - layout_node().computed_values().font_size()) / 2;
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}();
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if (auto length_percentage = layout_node().computed_values().vertical_align().get_pointer<CSS::LengthPercentage>(); length_percentage && length_percentage->is_length())
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bottom += length_percentage->length().to_px(layout_node());
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return bottom;
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}
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}
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@ -146,32 +146,37 @@ void LineBuilder::update_last_line()
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break;
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}
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auto fragment_baseline = [&](auto const& fragment) -> float {
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float fragment_baseline = 0;
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if (fragment.layout_node().is_text_node()) {
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fragment_baseline = fragment.layout_node().font().baseline();
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} else {
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auto const& box = verify_cast<Layout::Box>(fragment.layout_node());
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fragment_baseline = box_baseline(m_formatting_state, box);
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}
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return fragment_baseline;
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};
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auto line_box_baseline = [&] {
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float line_box_baseline = 0;
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for (auto& fragment : line_box.fragments()) {
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auto baseline = fragment_baseline(fragment);
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if (fragment.height() < m_context.containing_block().line_height())
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baseline += (m_context.containing_block().line_height() - fragment.height()) / 2;
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// NOTE: For fragments with a <length> vertical-align, shift the fragment baseline down by the length.
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auto const& font = fragment.layout_node().font();
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auto const line_height = fragment.layout_node().line_height();
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auto const font_metrics = font.pixel_metrics();
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auto const typographic_height = font_metrics.ascent + font_metrics.descent;
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auto const leading = line_height - typographic_height;
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auto const half_leading = leading / 2;
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// The CSS specification calls this AD (A+D, Ascent + Descent).
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float fragment_baseline = 0;
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if (fragment.layout_node().is_text_node()) {
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fragment_baseline = font_metrics.ascent;
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} else {
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auto const& box = verify_cast<Layout::Box>(fragment.layout_node());
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fragment_baseline = box_baseline(m_formatting_state, box);
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}
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fragment_baseline += half_leading;
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// Remember the baseline used for this fragment. This will be used when painting the fragment.
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fragment.set_baseline(fragment_baseline);
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// NOTE: For fragments with a <length> vertical-align, shift the line box baseline down by the length.
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// This ensures that we make enough vertical space on the line for any manually-aligned fragments.
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if (auto length_percentage = fragment.layout_node().computed_values().vertical_align().template get_pointer<CSS::LengthPercentage>(); length_percentage && length_percentage->is_length())
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baseline += length_percentage->length().to_px(fragment.layout_node());
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fragment_baseline += length_percentage->length().to_px(fragment.layout_node());
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// Store the baseline on the fragment. This is used when painting.
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fragment.set_baseline(baseline);
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line_box_baseline = max(line_box_baseline, baseline);
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line_box_baseline = max(line_box_baseline, fragment_baseline);
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}
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return line_box_baseline;
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}();
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@ -192,7 +197,7 @@ void LineBuilder::update_last_line()
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auto y_value_for_alignment = [&](CSS::VerticalAlign vertical_align) {
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switch (vertical_align) {
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case CSS::VerticalAlign::Baseline:
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return m_current_y + line_box_baseline - fragment_baseline(fragment) + fragment.border_box_top();
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return m_current_y + line_box_baseline - fragment.baseline() + fragment.border_box_top();
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case CSS::VerticalAlign::Top:
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return m_current_y + fragment.border_box_top();
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case CSS::VerticalAlign::Middle:
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@ -202,7 +207,7 @@ void LineBuilder::update_last_line()
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case CSS::VerticalAlign::TextBottom:
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case CSS::VerticalAlign::TextTop:
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// FIXME: These are all 'baseline'
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return m_current_y + line_box_baseline - fragment_baseline(fragment) + fragment.border_box_top();
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return m_current_y + line_box_baseline - fragment.baseline() + fragment.border_box_top();
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}
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VERIFY_NOT_REACHED();
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};
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@ -217,14 +222,34 @@ void LineBuilder::update_last_line()
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}
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}
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fragment.set_offset({ new_fragment_x, new_fragment_y });
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fragment.set_offset({ new_fragment_x, floorf(new_fragment_y) });
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uppermost_box_top = min(uppermost_box_top, fragment.top_of_inline_level_box(m_formatting_state));
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lowermost_box_bottom = max(lowermost_box_bottom, fragment.bottom_of_inline_level_box(m_formatting_state));
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float top_of_inline_box = 0;
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float bottom_of_inline_box = 0;
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{
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// FIXME: Support inline-table elements.
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if (fragment.layout_node().is_replaced_box() || fragment.layout_node().is_inline_block()) {
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auto const& fragment_box_state = m_formatting_state.get(static_cast<Box const&>(fragment.layout_node()));
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top_of_inline_box = fragment.offset().y() - fragment_box_state.margin_box_top();
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bottom_of_inline_box = fragment.offset().y() + fragment_box_state.content_height + fragment_box_state.margin_box_bottom();
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} else {
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auto font_metrics = fragment.layout_node().font().pixel_metrics();
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auto typographic_height = font_metrics.ascent + font_metrics.descent;
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auto leading = fragment.layout_node().line_height() - typographic_height;
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auto half_leading = leading / 2;
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top_of_inline_box = fragment.offset().y() + fragment.baseline() - font_metrics.ascent - half_leading;
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bottom_of_inline_box = fragment.offset().y() + fragment.baseline() + font_metrics.descent + half_leading;
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}
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if (auto length_percentage = fragment.layout_node().computed_values().vertical_align().template get_pointer<CSS::LengthPercentage>(); length_percentage && length_percentage->is_length())
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bottom_of_inline_box += length_percentage->length().to_px(fragment.layout_node());
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}
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uppermost_box_top = min(uppermost_box_top, top_of_inline_box);
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lowermost_box_bottom = max(lowermost_box_bottom, bottom_of_inline_box);
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}
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// 3. The line box height is the distance between the uppermost box top and the lowermost box bottom.
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line_box.m_height = max(m_context.containing_block().line_height(), lowermost_box_bottom - uppermost_box_top);
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line_box.m_height = lowermost_box_bottom - uppermost_box_top;
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line_box.m_bottom = m_current_y + line_box.m_height;
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line_box.m_baseline = line_box_baseline;
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@ -451,8 +451,13 @@ void PaintableWithLines::paint(PaintContext& context, PaintPhase phase) const
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for (auto& line_box : m_line_boxes) {
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for (auto& fragment : line_box.fragments()) {
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if (context.should_show_line_box_borders())
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context.painter().draw_rect(enclosing_int_rect(fragment.absolute_rect()), Color::Green);
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if (context.should_show_line_box_borders()) {
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auto fragment_absolute_rect = fragment.absolute_rect();
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context.painter().draw_rect(enclosing_int_rect(fragment_absolute_rect), Color::Green);
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context.painter().draw_line(
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fragment_absolute_rect.top_left().translated(0, fragment.baseline()).to_rounded<int>(),
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fragment_absolute_rect.top_right().translated(0, fragment.baseline()).to_rounded<int>(), Color::Red);
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}
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if (is<Layout::TextNode>(fragment.layout_node()))
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paint_text_fragment(context, static_cast<Layout::TextNode const&>(fragment.layout_node()), fragment, phase);
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}
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