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LibWeb: Move grapheme edge detection across lines to helper functions

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EditingHostManager is going to have exactly the same implementation as
FormAssociatedElement.
This commit is contained in:
Timothy Flynn 2025-08-20 15:16:21 -04:00 • committed by Tim Flynn
commit 42a5f66e41
Notes: github-actions[bot] 2025-09-18 11:40:47 +00:00
4 changed files with 127 additions and 90 deletions
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102
Libraries/LibWeb/HTML/FormAssociatedElement.cpp
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@ -27,7 +27,6 @@
#include <LibWeb/HTML/Parser/HTMLParser.h>
#include <LibWeb/HTML/ValidityState.h>
#include <LibWeb/Infra/Strings.h>
#include <LibWeb/Layout/TextNode.h>
#include <LibWeb/Painting/Paintable.h>
#include <LibWeb/Selection/Selection.h>
@ -1064,115 +1063,38 @@ void FormAssociatedTextControlElement::decrement_cursor_position_to_previous_wor
selection_was_changed();
}
static constexpr size_t find_line_start(Utf16View const& view, size_t offset)
{
while (offset != 0 && view.code_unit_at(offset - 1) != '\n')
--offset;
return offset;
}
static constexpr size_t find_line_end(Utf16View const& view, size_t offset)
{
auto length = view.length_in_code_units();
while (offset < length && view.code_unit_at(offset) != '\n')
++offset;
return offset;
}
static float measure_text_width(Layout::TextNode const& text_node, Utf16View const& text)
{
if (text.is_empty())
return 0;
auto segmenter = text_node.grapheme_segmenter().clone();
segmenter->set_segmented_text(text);
Layout::TextNode::ChunkIterator iterator { text_node, text, *segmenter, false, false };
float width = 0;
for (auto chunk = iterator.next(); chunk.has_value(); chunk = iterator.next())
width += chunk->font->width(chunk->view);
return width;
}
static size_t translate_position_across_lines(Layout::TextNode const& text_node, Utf16View const& source_line, Utf16View const& target_line)
{
GraphemeEdgeTracker tracker(measure_text_width(text_node, source_line));
auto previous_index = 0uz;
text_node.grapheme_segmenter().clone()->for_each_boundary(target_line, [&](auto index) {
auto current_width = measure_text_width(text_node, target_line.substring_view(previous_index, index - previous_index));
if (tracker.update(index - previous_index, current_width) == IterationDecision::Break)
return IterationDecision::Break;
previous_index = index;
return IterationDecision::Continue;
});
return tracker.resolve();
}
void FormAssociatedTextControlElement::increment_cursor_position_to_next_line(CollapseSelection collapse)
{
auto dom_node = form_associated_element_to_text_node();
if (!dom_node)
auto text_node = form_associated_element_to_text_node();
if (!text_node)
return;
auto const* layout_node = as_if<Layout::TextNode>(dom_node->layout_node());
if (!layout_node)
auto new_offset = compute_cursor_position_on_next_line(*text_node, m_selection_end);
if (!new_offset.has_value())
return;
auto text = dom_node->data().utf16_view();
auto new_offset = text.length_in_code_units();
if (auto current_line_end = find_line_end(text, m_selection_end); current_line_end < text.length_in_code_units()) {
auto current_line_start = find_line_start(text, m_selection_end);
auto current_line_text = text.substring_view(current_line_start, m_selection_end - current_line_start);
auto next_line_start = current_line_end + 1;
auto next_line_length = find_line_end(text, next_line_start) - next_line_start;
auto next_line_text = text.substring_view(next_line_start, next_line_length);
new_offset = next_line_start + translate_position_across_lines(*layout_node, current_line_text, next_line_text);
}
if (collapse == CollapseSelection::Yes)
collapse_selection_to_offset(new_offset);
collapse_selection_to_offset(*new_offset);
else
m_selection_end = new_offset;
m_selection_end = *new_offset;
selection_was_changed();
}
void FormAssociatedTextControlElement::decrement_cursor_position_to_previous_line(CollapseSelection collapse)
{
auto dom_node = form_associated_element_to_text_node();
if (!dom_node)
auto text_node = form_associated_element_to_text_node();
if (!text_node)
return;
auto const* layout_node = as_if<Layout::TextNode>(dom_node->layout_node());
if (!layout_node)
auto new_offset = compute_cursor_position_on_previous_line(*text_node, m_selection_end);
if (!new_offset.has_value())
return;
auto text = dom_node->data().utf16_view();
auto new_offset = 0uz;
if (auto current_line_start = find_line_start(text, m_selection_end); current_line_start != 0) {
auto current_line_text = text.substring_view(current_line_start, m_selection_end - current_line_start);
auto previous_line_start = find_line_start(text, current_line_start - 1);
auto previous_line_length = current_line_start - previous_line_start - 1;
auto previous_line_text = text.substring_view(previous_line_start, previous_line_length);
new_offset = previous_line_start + translate_position_across_lines(*layout_node, current_line_text, previous_line_text);
}
if (collapse == CollapseSelection::Yes)
collapse_selection_to_offset(new_offset);
collapse_selection_to_offset(*new_offset);
else
m_selection_end = new_offset;
m_selection_end = *new_offset;
selection_was_changed();
}