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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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52
Libraries/LibWeb/DOM/Text.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
*/
@ -75,30 +76,37 @@ WebIDL::ExceptionOr<GC::Ref<Text>> Text::split_text(size_t offset)
// 1. Insert new node into parent before node’s next sibling.
parent->insert_before(*new_node, next_sibling());
// 2. For each live range whose start node is node and start offset is greater than offset, set its start node to new node and decrease its start offset by offset.
for (auto& range : Range::live_ranges()) {
if (range->start_container() == this && range->start_offset() > offset)
TRY(range->set_start(*new_node, range->start_offset() - offset));
}
// 3. For each live range whose end node is node and end offset is greater than offset, set its end node to new node and decrease its end offset by offset.
for (auto& range : Range::live_ranges()) {
if (range->end_container() == this && range->end_offset() > offset)
TRY(range->set_end(*new_node, range->end_offset() - offset));
}
// 4. For each live range whose start node is parent and start offset is equal to the index of node plus 1, increase its start offset by 1.
for (auto& range : Range::live_ranges()) {
if (range->start_container() == parent.ptr() && range->start_offset() == index() + 1)
TRY(range->set_start(*range->start_container(), range->start_offset() + 1));
}
// 5. For each live range whose end node is parent and end offset is equal to the index of node plus 1, increase its end offset by 1.
for (auto& range : Range::live_ranges()) {
if (range->end_container() == parent.ptr() && range->end_offset() == index() + 1) {
TRY(range->set_end(*range->end_container(), range->end_offset() + 1));
// 2. For each live range whose start node is node and start offset is greater than offset, set its start node
// to new node and decrease its start offset by offset.
for (auto* range : Range::live_ranges()) {
if (range->start_container() == this && range->start_offset() > offset) {
range->set_start_node(*new_node);
range->decrease_start_offset(offset);
}
}
// 3. For each live range whose end node is node and end offset is greater than offset, set its end node to new
// node and decrease its end offset by offset.
for (auto* range : Range::live_ranges()) {
if (range->end_container() == this && range->end_offset() > offset) {
range->set_end_node(*new_node);
range->decrease_end_offset(offset);
}
}
// 4. For each live range whose start node is parent and start offset is equal to the index of node plus 1,
// increase its start offset by 1.
for (auto* range : Range::live_ranges()) {
if (range->start_container() == parent.ptr() && range->start_offset() == index() + 1)
range->increase_start_offset(1);
}
// 5. For each live range whose end node is parent and end offset is equal to the index of node plus 1, increase
// its end offset by 1.
for (auto* range : Range::live_ranges()) {
if (range->end_container() == parent.ptr() && range->end_offset() == index() + 1)
range->increase_end_offset(1);
}
}
// 8. Replace data with node node, offset offset, count count, and data the empty string.