mirrors/ladybird
0
0
Fork 0
mirror of https://github.com/LadybirdBrowser/ladybird.git synced 2025-09-13 13:02:28 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 9

LibWeb/CSS: Move An+B matching code into ANPlusBPattern::matches()

Browse source 
Not everything we want to match is an "nth element".

Also moved its serialization function's implementation out of the header
while I was at it.
This commit is contained in:
Sam Atkins 2025-08-12 11:17:26 +01:00
commit fbae3b824a
Notes: github-actions[bot] 2025-08-13 08:48:55 +00:00
3 changed files with 77 additions and 70 deletions
Download patch file Download diff file Expand all files Collapse all files

73
Libraries/LibWeb/CSS/Selector.cpp
View file

@ -823,4 +823,77 @@ SelectorList adapt_nested_relative_selector_list(SelectorList const& selectors)
return new_list;
}
// https://drafts.csswg.org/css-syntax-3/#anb-microsyntax
bool Selector::SimpleSelector::ANPlusBPattern::matches(int index) const
{
// "If both a and b are equal to zero, the pseudo-class represents no element in the document tree."
if (step_size == 0 && offset == 0)
return false;
// When "step_size == -1", selector represents first "offset" elements in document tree.
if (step_size == -1)
return !(offset <= 0 || index > offset);
// When "step_size == 1", selector represents last "offset" elements in document tree.
if (step_size == 1)
return !(offset < 0 || index < offset);
// When "step_size == 0", selector picks only the "offset" element.
if (step_size == 0)
return index == offset;
// If both are negative, nothing can match.
if (step_size < 0 && offset < 0)
return false;
// Like "a % b", but handles negative integers correctly.
auto const canonical_modulo = [](int a, int b) -> int {
int c = a % b;
if ((c < 0 && b > 0) || (c > 0 && b < 0)) {
c += b;
}
return c;
};
// When "step_size < 0", we start at "offset" and count backwards.
if (step_size < 0)
return index <= offset && canonical_modulo(index - offset, -step_size) == 0;
// Otherwise, we start at "offset" and count forwards.
return index >= offset && canonical_modulo(index - offset, step_size) == 0;
}
// https://drafts.csswg.org/css-syntax-3/#serializing-anb
String Selector::SimpleSelector::ANPlusBPattern::serialize() const
{
// 1. If A is zero, return the serialization of B.
if (step_size == 0)
return String::number(offset);
// 2. Otherwise, let result initially be an empty string.
StringBuilder result;
// 3.
// - A is 1: Append "n" to result.
if (step_size == 1)
result.append('n');
// - A is -1: Append "-n" to result.
else if (step_size == -1)
result.append("-n"sv);
// - A is non-zero: Serialize A and append it to result, then append "n" to result.
else if (step_size != 0)
result.appendff("{}n", step_size);
// 4.
// - B is greater than zero: Append "+" to result, then append the serialization of B to result.
if (offset > 0)
result.appendff("+{}", offset);
// - B is less than zero: Append the serialization of B to result.
else if (offset < 0)
result.appendff("{}", offset);
// 5. Return result.
return MUST(result.to_string());
}
}

35
Libraries/LibWeb/CSS/Selector.h
View file

@ -86,39 +86,8 @@ public:
int step_size { 0 }; // "A"
int offset = { 0 }; // "B"
// https://www.w3.org/TR/css-syntax-3/#serializing-anb
String serialize() const
{
// 1. If A is zero, return the serialization of B.
if (step_size == 0) {
return String::number(offset);
}
// 2. Otherwise, let result initially be an empty string.
StringBuilder result;
// 3.
// - A is 1: Append "n" to result.
if (step_size == 1)
result.append('n');
// - A is -1: Append "-n" to result.
else if (step_size == -1)
result.append("-n"sv);
// - A is non-zero: Serialize A and append it to result, then append "n" to result.
else if (step_size != 0)
result.appendff("{}n", step_size);
// 4.
// - B is greater than zero: Append "+" to result, then append the serialization of B to result.
if (offset > 0)
result.appendff("+{}", offset);
// - B is less than zero: Append the serialization of B to result.
if (offset < 0)
result.appendff("{}", offset);
// 5. Return result.
return MUST(result.to_string());
}
bool matches(int index) const;
String serialize() const;
};
struct PseudoClassSelector {

39
Libraries/LibWeb/CSS/SelectorEngine.cpp
View file

@ -1,6 +1,6 @@
/*
* Copyright (c) 2018-2024, Andreas Kling <andreas@ladybird.org>
* Copyright (c) 2021-2024, Sam Atkins <sam@ladybird.org>
* Copyright (c) 2021-2025, Sam Atkins <sam@ladybird.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -671,10 +671,6 @@ static inline bool matches_pseudo_class(CSS::Selector::SimpleSelector::PseudoCla
case CSS::PseudoClass::NthOfType:
case CSS::PseudoClass::NthLastOfType: {
auto& an_plus_b = pseudo_class.an_plus_b_patterns.first();
auto const step_size = an_plus_b.step_size;
auto const offset = an_plus_b.offset;
if (step_size == 0 && offset == 0)
return false; // "If both a and b are equal to zero, the pseudo-class represents no element in the document tree."
auto const* parent = element.parent();
if (!parent)
@ -730,38 +726,7 @@ static inline bool matches_pseudo_class(CSS::Selector::SimpleSelector::PseudoCla
default:
VERIFY_NOT_REACHED();
}
// When "step_size == -1", selector represents first "offset" elements in document tree.
if (step_size == -1)
return !(offset <= 0 || index > offset);
// When "step_size == 1", selector represents last "offset" elements in document tree.
if (step_size == 1)
return !(offset < 0 || index < offset);
// When "step_size == 0", selector picks only the "offset" element.
if (step_size == 0)
return index == offset;
// If both are negative, nothing can match.
if (step_size < 0 && offset < 0)
return false;
// Like "a % b", but handles negative integers correctly.
auto const canonical_modulo = [](int a, int b) -> int {
int c = a % b;
if ((c < 0 && b > 0) || (c > 0 && b < 0)) {
c += b;
}
return c;
};
// When "step_size < 0", we start at "offset" and count backwards.
if (step_size < 0)
return index <= offset && canonical_modulo(index - offset, -step_size) == 0;
// Otherwise, we start at "offset" and count forwards.
return index >= offset && canonical_modulo(index - offset, step_size) == 0;
return an_plus_b.matches(index);
}
case CSS::PseudoClass::Playing: {
if (!is<HTML::HTMLMediaElement>(element))