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ladybird/Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp
Sam Atkins ffc81cbfad LibWeb: Use Selectors instead of a String for :not() selectors 
Rather than parsing the selector every time we want to check it, we
now parse it once at the beginning.

A bonus effect of this is that we now support a selector list in
:not(), instead of just a single selector, though only when using
the new parser.
2021-07-14 13:31:00 +02:00

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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Sam Atkins <atkinssj@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/CSS/Parser/DeprecatedCSSParser.h>
#include <LibWeb/CSS/SelectorEngine.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/Element.h>
#include <LibWeb/DOM/Text.h>
#include <LibWeb/HTML/AttributeNames.h>
#include <LibWeb/HTML/HTMLElement.h>
namespace Web::SelectorEngine {
static bool matches_hover_pseudo_class(DOM::Element const& element)
{
auto* hovered_node = element.document().hovered_node();
if (!hovered_node)
return false;
if (&element == hovered_node)
return true;
return element.is_ancestor_of(*hovered_node);
}
static bool matches_attribute(CSS::Selector::SimpleSelector::Attribute const& attribute, DOM::Element const& element)
{
switch (attribute.match_type) {
case CSS::Selector::SimpleSelector::Attribute::MatchType::HasAttribute:
return element.has_attribute(attribute.name);
break;
case CSS::Selector::SimpleSelector::Attribute::MatchType::ExactValueMatch:
return element.attribute(attribute.name) == attribute.value;
break;
case CSS::Selector::SimpleSelector::Attribute::MatchType::ContainsWord:
return element.attribute(attribute.name).split(' ').contains_slow(attribute.value);
break;
case CSS::Selector::SimpleSelector::Attribute::MatchType::ContainsString:
return element.attribute(attribute.name).contains(attribute.value);
break;
case CSS::Selector::SimpleSelector::Attribute::MatchType::StartsWithSegment:
return element.attribute(attribute.name).split('-').first() == attribute.value;
break;
case CSS::Selector::SimpleSelector::Attribute::MatchType::StartsWithString:
return element.attribute(attribute.name).starts_with(attribute.value);
break;
case CSS::Selector::SimpleSelector::Attribute::MatchType::EndsWithString:
return element.attribute(attribute.name).ends_with(attribute.value);
break;
case CSS::Selector::SimpleSelector::Attribute::MatchType::None:
VERIFY_NOT_REACHED();
break;
}
return false;
}
static bool matches_pseudo_class(CSS::Selector::SimpleSelector::PseudoClass const& pseudo_class, DOM::Element const& element)
{
switch (pseudo_class.type) {
case CSS::Selector::SimpleSelector::PseudoClass::Type::None:
break;
case CSS::Selector::SimpleSelector::PseudoClass::Type::Link:
return element.is_link();
case CSS::Selector::SimpleSelector::PseudoClass::Type::Visited:
// FIXME: Maybe match this selector sometimes?
return false;
case CSS::Selector::SimpleSelector::PseudoClass::Type::Active:
return element.is_active();
case CSS::Selector::SimpleSelector::PseudoClass::Type::Hover:
return matches_hover_pseudo_class(element);
case CSS::Selector::SimpleSelector::PseudoClass::Type::Focus:
return element.is_focused();
case CSS::Selector::SimpleSelector::PseudoClass::Type::FirstChild:
return !element.previous_element_sibling();
case CSS::Selector::SimpleSelector::PseudoClass::Type::LastChild:
return !element.next_element_sibling();
case CSS::Selector::SimpleSelector::PseudoClass::Type::OnlyChild:
return !(element.previous_element_sibling() || element.next_element_sibling());
case CSS::Selector::SimpleSelector::PseudoClass::Type::Empty:
return !(element.first_child_of_type<DOM::Element>() || element.first_child_of_type<DOM::Text>());
case CSS::Selector::SimpleSelector::PseudoClass::Type::Root:
return is<HTML::HTMLElement>(element);
case CSS::Selector::SimpleSelector::PseudoClass::Type::FirstOfType:
for (auto* sibling = element.previous_element_sibling(); sibling; sibling = sibling->previous_element_sibling()) {
if (sibling->tag_name() == element.tag_name())
return false;
}
return true;
case CSS::Selector::SimpleSelector::PseudoClass::Type::LastOfType:
for (auto* sibling = element.next_element_sibling(); sibling; sibling = sibling->next_element_sibling()) {
if (sibling->tag_name() == element.tag_name())
return false;
}
return true;
case CSS::Selector::SimpleSelector::PseudoClass::Type::Disabled:
if (!element.tag_name().equals_ignoring_case(HTML::TagNames::input))
return false;
if (!element.has_attribute("disabled"))
return false;
return true;
case CSS::Selector::SimpleSelector::PseudoClass::Type::Enabled:
if (!element.tag_name().equals_ignoring_case(HTML::TagNames::input))
return false;
if (element.has_attribute("disabled"))
return false;
return true;
case CSS::Selector::SimpleSelector::PseudoClass::Type::Checked:
if (!element.tag_name().equals_ignoring_case(HTML::TagNames::input))
return false;
if (!element.has_attribute("checked"))
return false;
return true;
case CSS::Selector::SimpleSelector::PseudoClass::Type::Not:
for (auto& selector : pseudo_class.not_selector) {
if (matches(selector, element))
return false;
}
return true;
case CSS::Selector::SimpleSelector::PseudoClass::Type::NthChild:
case CSS::Selector::SimpleSelector::PseudoClass::Type::NthLastChild:
auto const step_size = pseudo_class.nth_child_pattern.step_size;
auto const offset = pseudo_class.nth_child_pattern.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_element();
if (!parent)
return false;
int index = 1;
if (pseudo_class.type == CSS::Selector::SimpleSelector::PseudoClass::Type::NthChild) {
for (auto* child = parent->first_child_of_type<DOM::Element>(); child && child != &element; child = child->next_element_sibling())
++index;
} else {
for (auto* child = parent->last_child_of_type<DOM::Element>(); child && child != &element; child = child->previous_element_sibling())
++index;
}
if (step_size < 0) {
// When "step_size" is negative, selector represents first "offset" elements in document tree.
return !(offset <= 0 || index > offset);
} else if (step_size == 1) {
// When "step_size == 1", selector represents last "offset" elements in document tree.
return !(offset < 0 || index < offset);
}
// 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;
};
if (step_size == 0) {
// Avoid divide by zero.
if (index != offset) {
return false;
}
} else if (canonical_modulo(index - offset, step_size) != 0) {
return false;
}
return true;
}
return false;
}
static bool matches(CSS::Selector::SimpleSelector const& component, DOM::Element const& element)
{
switch (component.type) {
case CSS::Selector::SimpleSelector::Type::Universal:
return true;
case CSS::Selector::SimpleSelector::Type::Id:
return component.value == element.attribute(HTML::AttributeNames::id);
case CSS::Selector::SimpleSelector::Type::Class:
return element.has_class(component.value);
case CSS::Selector::SimpleSelector::Type::TagName:
return component.value == element.local_name();
case CSS::Selector::SimpleSelector::Type::Attribute:
return matches_attribute(component.attribute, element);
case CSS::Selector::SimpleSelector::Type::PseudoClass:
return matches_pseudo_class(component.pseudo_class, element);
case CSS::Selector::SimpleSelector::Type::PseudoElement:
// FIXME: Implement pseudo-elements.
return false;
default:
VERIFY_NOT_REACHED();
}
}
static bool matches(CSS::Selector const& selector, int component_list_index, DOM::Element const& element)
{
auto& component_list = selector.complex_selectors()[component_list_index];
for (auto& component : component_list.compound_selector) {
if (!matches(component, element))
return false;
}
switch (component_list.relation) {
case CSS::Selector::ComplexSelector::Relation::None:
return true;
case CSS::Selector::ComplexSelector::Relation::Descendant:
VERIFY(component_list_index != 0);
for (auto* ancestor = element.parent(); ancestor; ancestor = ancestor->parent()) {
if (!is<DOM::Element>(*ancestor))
continue;
if (matches(selector, component_list_index - 1, verify_cast<DOM::Element>(*ancestor)))
return true;
}
return false;
case CSS::Selector::ComplexSelector::Relation::ImmediateChild:
VERIFY(component_list_index != 0);
if (!element.parent() || !is<DOM::Element>(*element.parent()))
return false;
return matches(selector, component_list_index - 1, verify_cast<DOM::Element>(*element.parent()));
case CSS::Selector::ComplexSelector::Relation::AdjacentSibling:
VERIFY(component_list_index != 0);
if (auto* sibling = element.previous_element_sibling())
return matches(selector, component_list_index - 1, *sibling);
return false;
case CSS::Selector::ComplexSelector::Relation::GeneralSibling:
VERIFY(component_list_index != 0);
for (auto* sibling = element.previous_element_sibling(); sibling; sibling = sibling->previous_element_sibling()) {
if (matches(selector, component_list_index - 1, *sibling))
return true;
}
return false;
case CSS::Selector::ComplexSelector::Relation::Column:
TODO();
}
VERIFY_NOT_REACHED();
}
bool matches(CSS::Selector const& selector, DOM::Element const& element)
{
VERIFY(!selector.complex_selectors().is_empty());
return matches(selector, selector.complex_selectors().size() - 1, element);
}
}
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