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f05bc7c0cd
This property determines the default baseline used to align content within the given box.
63 lines
2.2 KiB
C++
63 lines
2.2 KiB
C++
/*
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* Copyright (c) 2026, Tim Ledbetter <tim.ledbetter@ladybird.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <LibGfx/Font/Font.h>
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#include <LibWeb/CSS/ComputedValues.h>
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namespace Web::Layout {
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// https://drafts.csswg.org/css-inline/#dominant-baseline-property
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static float dominant_baseline_offset(CSS::BaselineMetric metric, Gfx::FontPixelMetrics const& font_metrics)
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{
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switch (metric) {
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case CSS::BaselineMetric::Central:
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return (font_metrics.ascent - font_metrics.descent) / 2;
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case CSS::BaselineMetric::Middle:
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return font_metrics.x_height / 2;
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case CSS::BaselineMetric::Hanging:
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// FIXME: Read the hanging baseline from the font's BASE table.
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return font_metrics.ascent * 0.8f;
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case CSS::BaselineMetric::Ideographic:
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// FIXME: Read the ideographic baseline from the font's BASE table.
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return -font_metrics.descent;
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case CSS::BaselineMetric::Mathematical:
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// FIXME: Read the math baseline from the font's BASE table.
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return font_metrics.ascent * 0.5f;
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case CSS::BaselineMetric::TextTop:
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case CSS::BaselineMetric::TextBottom:
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// FIXME: Support text-top and text-bottom.
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case CSS::BaselineMetric::Alphabetic:
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return 0;
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}
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VERIFY_NOT_REACHED();
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}
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static CSS::BaselineMetric resolve_dominant_baseline_metric(CSS::ComputedValues const& computed_values)
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{
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auto dominant_baseline = computed_values.dominant_baseline();
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if (dominant_baseline.has_value())
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return *dominant_baseline;
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// https://drafts.csswg.org/css-inline/#valdef-dominant-baseline-auto
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// Equivalent to alphabetic in horizontal writing modes and in vertical writing modes when text-orientation is
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// sideways. Equivalent to central in vertical writing modes when text-orientation is mixed or upright.
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// FIXME: Take text-orientation into account once it is implemented.
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switch (computed_values.writing_mode()) {
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case CSS::WritingMode::HorizontalTb:
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case CSS::WritingMode::SidewaysRl:
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case CSS::WritingMode::SidewaysLr:
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return CSS::BaselineMetric::Alphabetic;
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case CSS::WritingMode::VerticalRl:
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case CSS::WritingMode::VerticalLr:
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return CSS::BaselineMetric::Central;
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}
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VERIFY_NOT_REACHED();
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}
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}
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