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LibWeb: Modify range start & end directly where applicable

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We were calling into `Range::set_start_or_end()` indirectly through
`::set_start()` and `::set_end()`, but that algorithm only calls for an
invocation whenever the start or end of a range needs to be set to a
boundary point. If an algorithm step calls for setting the node or
offset, we should directly modify the range.

The problem with calling into `::set_start_or_end()` is that this
algorithm potentially modifies _both_ the start and end of the range,
but algorithms trying to update a range's start or end often have
explicit steps to take both the start and end into account and end up
overcompensating for the start or end offset resulting in an invalid
range (e.g. with an end offset beyond a node's length).

This makes updating a range's start/end a bit more efficient and removes
a piece of ad-hoc code in CharacterData needed to make it work before.
This commit is contained in:
Jelle Raaijmakers 2025-05-14 12:56:03 +02:00 • committed by Tim Ledbetter
commit 0d83426a49
Notes: github-actions[bot] 2025-05-15 10:45:47 +00:00
5 changed files with 112 additions and 95 deletions
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35
Libraries/LibWeb/DOM/CharacterData.cpp
View file

@ -1,5 +1,6 @@
/*
* Copyright (c) 2018-2022, Andreas Kling <andreas@ladybird.org>
* Copyright (c) 2025, Jelle Raaijmakers <jelle@ladybird.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -10,7 +11,6 @@
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/MutationType.h>
#include <LibWeb/DOM/Range.h>
#include <LibWeb/DOM/StaticNodeList.h>
#include <LibWeb/Layout/TextNode.h>
namespace Web::DOM {
@ -105,31 +105,32 @@ WebIDL::ExceptionOr<void> CharacterData::replace_data(size_t offset, size_t coun
// NOTE: We do this later so that the mutation observer may notify UI clients of this node's new value.
queue_mutation_record(MutationType::characterData, {}, {}, old_data, {}, {}, nullptr, nullptr);
// 8. For each live range whose start node is node and start offset is greater than offset but less than or equal to offset plus count, set its start offset to offset.
for (auto& range : Range::live_ranges()) {
// 8. For each live range whose start node is node and start offset is greater than offset but less than or equal to
// offset plus count, set its start offset to offset.
for (auto* range : Range::live_ranges()) {
if (range->start_container() == this && range->start_offset() > offset && range->start_offset() <= (offset + count))
TRY(range->set_start(*range->start_container(), offset));
range->set_start_offset(offset);
}
// 9. For each live range whose end node is node and end offset is greater than offset but less than or equal to offset plus count, set its end offset to offset.
for (auto& range : Range::live_ranges()) {
// 9. For each live range whose end node is node and end offset is greater than offset but less than or equal to
// offset plus count, set its end offset to offset.
for (auto* range : Range::live_ranges()) {
if (range->end_container() == this && range->end_offset() > offset && range->end_offset() <= (offset + count))
TRY(range->set_end(*range->end_container(), offset));
range->set_end_offset(offset);
}
// 10. For each live range whose start node is node and start offset is greater than offset plus count, increase its start offset by data’s length and decrease it by count.
for (auto& range : Range::live_ranges()) {
// 10. For each live range whose start node is node and start offset is greater than offset plus count, increase its
// start offset by data’s length and decrease it by count.
for (auto* range : Range::live_ranges()) {
if (range->start_container() == this && range->start_offset() > (offset + count))
TRY(range->set_start(*range->start_container(), range->start_offset() + inserted_data_result.data.size() - count));
range->set_start_offset(range->start_offset() + inserted_data_result.data.size() - count);
}
// 11. For each live range whose end node is node and end offset is greater than offset plus count, increase its end offset by data’s length and decrease it by count.
for (auto& range : Range::live_ranges()) {
if (range->end_container() == this && range->end_offset() > (offset + count)) {
// AD-HOC: Clamp offset to the end of the data if it's too large.
auto new_offset = min(range->end_offset() + inserted_data_result.data.size() - count, length_in_utf16_code_units());
TRY(range->set_end(*range->end_container(), new_offset));
}
// 11. For each live range whose end node is node and end offset is greater than offset plus count, increase its end
// offset by data’s length and decrease it by count.
for (auto* range : Range::live_ranges()) {
if (range->end_container() == this && range->end_offset() > (offset + count))
range->set_end_offset(range->end_offset() + inserted_data_result.data.size() - count);
}
// 12. If node’s parent is non-null, then run the children changed steps for node’s parent.