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Instead of using the first font from the FontCascadeList for all glyphs in a text, we perform a text shaping process that finds a suitable font for each glyph and returns a list of glyph runs, where each glyph run represents consecutive glyphs using the same font.
113 lines
4.2 KiB
C++
113 lines
4.2 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <andreas@ladybird.org>
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* Copyright (c) 2021, sin-ack <sin-ack@protonmail.com>
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* Copyright (c) 2024-2025, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "TextLayout.h"
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#include <AK/TypeCasts.h>
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#include <LibGfx/Point.h>
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#include <harfbuzz/hb.h>
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namespace Gfx {
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Vector<NonnullRefPtr<GlyphRun>> shape_text(FloatPoint baseline_start, Utf8View string, FontCascadeList const& font_cascade_list)
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{
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if (string.length() == 0)
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return {};
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Vector<NonnullRefPtr<GlyphRun>> runs;
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auto it = string.begin();
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auto substring_begin_offset = string.iterator_offset(it);
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Font const* last_font = &font_cascade_list.font_for_code_point(*it);
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FloatPoint last_position = baseline_start;
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auto add_run = [&runs, &last_position](Utf8View string, Font const& font) {
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auto run = shape_text(last_position, 0, string, font, GlyphRun::TextType::Common, {});
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last_position.translate_by(run->width(), 0);
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runs.append(*run);
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};
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while (it != string.end()) {
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auto code_point = *it;
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auto const* font = &font_cascade_list.font_for_code_point(code_point);
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if (font != last_font) {
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auto substring = string.substring_view(substring_begin_offset, string.iterator_offset(it) - substring_begin_offset);
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add_run(substring, *last_font);
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last_font = font;
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substring_begin_offset = string.iterator_offset(it);
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}
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++it;
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}
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auto end_offset = string.iterator_offset(it);
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if (substring_begin_offset < end_offset) {
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auto substring = string.substring_view(substring_begin_offset, end_offset - substring_begin_offset);
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add_run(substring, *last_font);
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}
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return runs;
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}
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RefPtr<GlyphRun> shape_text(FloatPoint baseline_start, float letter_spacing, Utf8View string, Gfx::Font const& font, GlyphRun::TextType text_type, ShapeFeatures const& features)
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{
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static hb_buffer_t* buffer = hb_buffer_create();
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hb_buffer_add_utf8(buffer, reinterpret_cast<char const*>(string.bytes()), string.byte_length(), 0, -1);
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hb_buffer_guess_segment_properties(buffer);
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u32 glyph_count;
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auto* glyph_info = hb_buffer_get_glyph_infos(buffer, &glyph_count);
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Vector<hb_glyph_info_t> const input_glyph_info({ glyph_info, glyph_count });
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auto* hb_font = font.harfbuzz_font();
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hb_feature_t const* hb_features_data = nullptr;
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Vector<hb_feature_t> hb_features;
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if (!features.is_empty()) {
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hb_features.ensure_capacity(features.size());
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for (auto const& feature : features) {
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hb_features.append({
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.tag = HB_TAG(feature.tag[0], feature.tag[1], feature.tag[2], feature.tag[3]),
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.value = feature.value,
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.start = 0,
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.end = HB_FEATURE_GLOBAL_END,
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});
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}
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hb_features_data = hb_features.data();
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}
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hb_shape(hb_font, buffer, hb_features_data, features.size());
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glyph_info = hb_buffer_get_glyph_infos(buffer, &glyph_count);
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auto* positions = hb_buffer_get_glyph_positions(buffer, &glyph_count);
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Vector<Gfx::DrawGlyph> glyph_run;
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FloatPoint point = baseline_start;
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for (size_t i = 0; i < glyph_count; ++i) {
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auto position = point
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- FloatPoint { 0, font.pixel_metrics().ascent }
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+ FloatPoint { positions[i].x_offset, positions[i].y_offset } / text_shaping_resolution;
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glyph_run.append({ position, glyph_info[i].codepoint });
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point += FloatPoint { positions[i].x_advance, positions[i].y_advance } / text_shaping_resolution;
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// don't apply spacing to last glyph
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// https://drafts.csswg.org/css-text/#example-7880704e
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if (i != (glyph_count - 1))
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point.translate_by(letter_spacing, 0);
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}
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auto run = adopt_ref(*new Gfx::GlyphRun(move(glyph_run), font, text_type, point.x() - baseline_start.x()));
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hb_buffer_reset(buffer);
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return run;
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}
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float measure_text_width(Utf8View const& string, Gfx::Font const& font, ShapeFeatures const& features)
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{
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auto glyph_run = shape_text({}, 0, string, font, GlyphRun::TextType::Common, features);
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return glyph_run->width();
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}
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}
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