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3df83dade8
We generated `PaintableFragment`s with a start and length represented in UTF-8 byte offsets, but failed to consider that the offsets in a `DOM::Range` are actually expressed in UTF-16 code units. This is a bit of a mess: almost all web specs use UTF-16 code units as the unit for indexing into text nodes, but we almost exclusively use UTF-8 in our code base. Arguably the best thing would for us to use UTF-16 everywhere as well: it prevents these mismatches in our implementations for the price of a bit more memory usage - and even that could potentially be optimized for. But for now, try to do the correct thing and lazily allocate UTF-16 data in a `PaintableFragment` whenever we need to index into it or if we're asked to determine the code unit offset of a pixel position.
260 lines
10 KiB
C++
260 lines
10 KiB
C++
/*
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* Copyright (c) 2024, 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 <LibWeb/DOM/Range.h>
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#include <LibWeb/HTML/FormAssociatedElement.h>
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#include <LibWeb/HTML/HTMLInputElement.h>
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#include <LibWeb/HTML/HTMLTextAreaElement.h>
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#include <LibWeb/Layout/Viewport.h>
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#include <LibWeb/Painting/PaintableBox.h>
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#include <LibWeb/Painting/TextPaintable.h>
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namespace Web::Painting {
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PaintableFragment::PaintableFragment(Layout::LineBoxFragment const& fragment)
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: m_layout_node(fragment.layout_node())
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, m_offset(fragment.offset())
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, m_size(fragment.size())
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, m_baseline(fragment.baseline())
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, m_start(fragment.start())
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, m_length(fragment.length())
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, m_glyph_run(fragment.glyph_run())
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, m_writing_mode(fragment.writing_mode())
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{
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}
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CSSPixelRect const PaintableFragment::absolute_rect() const
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{
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CSSPixelRect rect { {}, size() };
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if (auto const* containing_block = paintable().containing_block())
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rect.set_location(containing_block->absolute_position());
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rect.translate_by(offset());
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return rect;
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}
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size_t PaintableFragment::index_in_node_for_byte_offset(size_t byte_offset) const
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{
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if (m_length == 0)
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return 0;
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if (byte_offset >= m_start + m_length)
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return utf16_view().length_in_code_units();
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auto code_point_offset = utf8_view().code_point_offset_of(byte_offset);
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return utf16_view().code_unit_offset_of(code_point_offset);
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}
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size_t PaintableFragment::index_in_node_for_point(CSSPixelPoint position) const
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{
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if (!is<TextPaintable>(paintable()))
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return 0;
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auto relative_inline_offset = [&] {
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switch (orientation()) {
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case Orientation::Horizontal:
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return (position.x() - absolute_rect().x()).to_float();
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case Orientation::Vertical:
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return (position.y() - absolute_rect().y()).to_float();
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}
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VERIFY_NOT_REACHED();
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}();
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if (relative_inline_offset < 0)
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return 0;
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// Find the code point offset of the glyph matching the position.
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auto code_point_offset = utf8_view().code_point_offset_of(m_start);
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auto const& glyphs = m_glyph_run->glyphs();
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auto smallest_distance = AK::NumericLimits<float>::max();
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for (size_t i = 0; i < glyphs.size(); ++i) {
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auto distance_to_position = AK::abs(glyphs[i].position.x() - relative_inline_offset);
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// The last distance was smaller than this new distance, so we've found the closest glyph.
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if (distance_to_position > smallest_distance)
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break;
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smallest_distance = distance_to_position;
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++code_point_offset;
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}
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// Return the code unit offset in the UTF-16 string.
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return utf16_view().code_unit_offset_of(code_point_offset - 1);
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}
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CSSPixelRect PaintableFragment::range_rect(size_t start_offset_in_code_units, size_t end_offset_in_code_units) const
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{
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if (paintable().selection_state() == Paintable::SelectionState::None)
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return {};
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if (paintable().selection_state() == Paintable::SelectionState::Full)
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return absolute_rect();
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auto const& font = glyph_run() ? glyph_run()->font() : layout_node().first_available_font();
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// We are invoked with offsets coming from a Range, which means they are expressed in UTF-16 code units. We need to
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// convert them to the byte offsets in the UTF-8 string. This is inefficient, but we only need to do it for
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// fragments with a partial selection.
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auto code_unit_to_byte_offset = [&](size_t offset_in_code_units) -> size_t {
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auto text_in_utf16 = utf16_view();
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if (offset_in_code_units >= text_in_utf16.length_in_code_units())
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return m_length;
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auto offset_code_point = text_in_utf16.code_point_offset_of(offset_in_code_units);
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auto byte_offset = utf8_view().byte_offset_of(offset_code_point);
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if (byte_offset <= m_start)
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return 0;
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if (byte_offset > m_start + m_length)
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return m_length;
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return byte_offset - m_start;
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};
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// We operate on the UTF-8 string that is part of this fragment.
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auto text = utf8_view().substring_view(m_start, m_length);
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if (paintable().selection_state() == Paintable::SelectionState::StartAndEnd) {
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auto selection_start_in_this_fragment = code_unit_to_byte_offset(start_offset_in_code_units);
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auto selection_end_in_this_fragment = code_unit_to_byte_offset(end_offset_in_code_units);
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// we are in the start/end node (both the same)
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if (selection_start_in_this_fragment >= m_length)
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return {};
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if (selection_end_in_this_fragment == 0)
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return {};
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if (selection_start_in_this_fragment == selection_end_in_this_fragment)
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return {};
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auto pixel_distance_to_first_selected_character = CSSPixels::nearest_value_for(font.width(text.substring_view(0, selection_start_in_this_fragment)));
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auto pixel_width_of_selection = CSSPixels::nearest_value_for(font.width(text.substring_view(selection_start_in_this_fragment, selection_end_in_this_fragment - selection_start_in_this_fragment))) + 1;
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auto rect = absolute_rect();
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switch (orientation()) {
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case Gfx::Orientation::Horizontal:
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rect.set_x(rect.x() + pixel_distance_to_first_selected_character);
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rect.set_width(pixel_width_of_selection);
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break;
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case Gfx::Orientation::Vertical:
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rect.set_y(rect.y() + pixel_distance_to_first_selected_character);
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rect.set_height(pixel_width_of_selection);
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break;
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default:
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VERIFY_NOT_REACHED();
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}
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return rect;
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}
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if (paintable().selection_state() == Paintable::SelectionState::Start) {
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auto selection_start_in_this_fragment = code_unit_to_byte_offset(start_offset_in_code_units);
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auto selection_end_in_this_fragment = m_length;
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// we are in the start node
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if (selection_start_in_this_fragment >= m_length)
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return {};
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auto pixel_distance_to_first_selected_character = CSSPixels::nearest_value_for(font.width(text.substring_view(0, selection_start_in_this_fragment)));
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auto pixel_width_of_selection = CSSPixels::nearest_value_for(font.width(text.substring_view(selection_start_in_this_fragment, selection_end_in_this_fragment - selection_start_in_this_fragment))) + 1;
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auto rect = absolute_rect();
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switch (orientation()) {
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case Gfx::Orientation::Horizontal:
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rect.set_x(rect.x() + pixel_distance_to_first_selected_character);
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rect.set_width(pixel_width_of_selection);
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break;
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case Gfx::Orientation::Vertical:
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rect.set_y(rect.y() + pixel_distance_to_first_selected_character);
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rect.set_height(pixel_width_of_selection);
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break;
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default:
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VERIFY_NOT_REACHED();
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}
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return rect;
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}
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if (paintable().selection_state() == Paintable::SelectionState::End) {
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auto selection_start_in_this_fragment = 0u;
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auto selection_end_in_this_fragment = code_unit_to_byte_offset(end_offset_in_code_units);
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// we are in the end node
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if (selection_end_in_this_fragment == 0)
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return {};
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auto pixel_distance_to_first_selected_character = CSSPixels::nearest_value_for(font.width(text.substring_view(0, selection_start_in_this_fragment)));
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auto pixel_width_of_selection = CSSPixels::nearest_value_for(font.width(text.substring_view(selection_start_in_this_fragment, selection_end_in_this_fragment - selection_start_in_this_fragment))) + 1;
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auto rect = absolute_rect();
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switch (orientation()) {
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case Gfx::Orientation::Horizontal:
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rect.set_x(rect.x() + pixel_distance_to_first_selected_character);
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rect.set_width(pixel_width_of_selection);
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break;
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case Gfx::Orientation::Vertical:
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rect.set_y(rect.y() + pixel_distance_to_first_selected_character);
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rect.set_height(pixel_width_of_selection);
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break;
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default:
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VERIFY_NOT_REACHED();
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}
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return rect;
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}
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return {};
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}
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Gfx::Orientation PaintableFragment::orientation() const
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{
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switch (m_writing_mode) {
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case CSS::WritingMode::HorizontalTb:
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return Gfx::Orientation::Horizontal;
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case CSS::WritingMode::VerticalRl:
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case CSS::WritingMode::VerticalLr:
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case CSS::WritingMode::SidewaysRl:
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case CSS::WritingMode::SidewaysLr:
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return Gfx::Orientation::Vertical;
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default:
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VERIFY_NOT_REACHED();
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}
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}
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CSSPixelRect PaintableFragment::selection_rect() const
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{
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if (auto const* focused_element = paintable().document().focused_element(); focused_element && is<HTML::FormAssociatedTextControlElement>(*focused_element)) {
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HTML::FormAssociatedTextControlElement const* text_control_element = nullptr;
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if (is<HTML::HTMLInputElement>(*focused_element)) {
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text_control_element = static_cast<HTML::HTMLInputElement const*>(focused_element);
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} else if (is<HTML::HTMLTextAreaElement>(*focused_element)) {
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text_control_element = static_cast<HTML::HTMLTextAreaElement const*>(focused_element);
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} else {
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VERIFY_NOT_REACHED();
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}
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auto selection_start = text_control_element->selection_start();
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auto selection_end = text_control_element->selection_end();
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return range_rect(selection_start, selection_end);
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}
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auto selection = paintable().document().get_selection();
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if (!selection)
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return {};
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auto range = selection->range();
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if (!range)
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return {};
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return range_rect(range->start_offset(), range->end_offset());
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}
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Utf8View PaintableFragment::utf8_view() const
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{
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if (!is<TextPaintable>(paintable()))
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return {};
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return Utf8View { static_cast<TextPaintable const&>(paintable()).text_for_rendering() };
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}
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Utf16View PaintableFragment::utf16_view() const
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{
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if (!is<TextPaintable>(paintable()))
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return {};
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if (!m_text_in_utf16.has_value())
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m_text_in_utf16 = MUST(AK::utf8_to_utf16(utf8_view()));
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return Utf16View { m_text_in_utf16.value() };
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}
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}
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