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ladybird/Userland/Libraries/LibWeb/CSS/SelectorEngine.cpp
Kenneth Myhra be958a14cf LibWeb: Use from_deprecated_fly_string() instead of from_utf8() 
Use FlyString::from_deprecated_fly_string() in these instances instead
of FlyString::from_utf8(). As we convert to new FlyString/String we want
to be aware of these potential unnecessary allocations.
2023-03-11 18:32:33 +00:00

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/*
* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021-2023, Sam Atkins <atkinssj@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibWeb/CSS/Parser/Parser.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/HTMLAnchorElement.h>
#include <LibWeb/HTML/HTMLAreaElement.h>
#include <LibWeb/HTML/HTMLButtonElement.h>
#include <LibWeb/HTML/HTMLFieldSetElement.h>
#include <LibWeb/HTML/HTMLHtmlElement.h>
#include <LibWeb/HTML/HTMLInputElement.h>
#include <LibWeb/HTML/HTMLOptGroupElement.h>
#include <LibWeb/HTML/HTMLOptionElement.h>
#include <LibWeb/HTML/HTMLSelectElement.h>
#include <LibWeb/HTML/HTMLTextAreaElement.h>
#include <LibWeb/Infra/Strings.h>
namespace Web::SelectorEngine {
// https://drafts.csswg.org/selectors-4/#the-lang-pseudo
static inline bool matches_lang_pseudo_class(DOM::Element const& element, Vector<FlyString> const& languages)
{
FlyString element_language;
for (auto const* e = &element; e; e = e->parent_element()) {
auto lang = e->attribute(HTML::AttributeNames::lang);
if (!lang.is_null()) {
element_language = FlyString::from_deprecated_fly_string(lang).release_value_but_fixme_should_propagate_errors();
break;
}
}
if (element_language.is_empty())
return false;
// FIXME: This is ad-hoc. Implement a proper language range matching algorithm as recommended by BCP47.
for (auto const& language : languages) {
if (language.is_empty())
return false;
if (language == "*"sv)
return true;
if (!element_language.to_string().contains('-'))
return Infra::is_ascii_case_insensitive_match(element_language, language);
auto parts = element_language.to_string().split_limit('-', 2).release_value_but_fixme_should_propagate_errors();
return Infra::is_ascii_case_insensitive_match(parts[0], language);
}
return false;
}
// https://html.spec.whatwg.org/multipage/semantics-other.html#selector-link
static inline bool matches_link_pseudo_class(DOM::Element const& element)
{
// All a elements that have an href attribute, and all area elements that have an href attribute, must match one of :link and :visited.
if (!is<HTML::HTMLAnchorElement>(element) && !is<HTML::HTMLAreaElement>(element))
return false;
return element.has_attribute(HTML::AttributeNames::href);
}
static inline 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);
}
// https://html.spec.whatwg.org/multipage/semantics-other.html#selector-checked
static inline bool matches_checked_pseudo_class(DOM::Element const& element)
{
// The :checked pseudo-class must match any element falling into one of the following categories:
// - input elements whose type attribute is in the Checkbox state and whose checkedness state is true
// - input elements whose type attribute is in the Radio Button state and whose checkedness state is true
if (is<HTML::HTMLInputElement>(element)) {
auto const& input_element = static_cast<HTML::HTMLInputElement const&>(element);
switch (input_element.type_state()) {
case HTML::HTMLInputElement::TypeAttributeState::Checkbox:
case HTML::HTMLInputElement::TypeAttributeState::RadioButton:
return static_cast<HTML::HTMLInputElement const&>(element).checked();
default:
return false;
}
}
// FIXME: - option elements whose selectedness is true
return false;
}
static inline bool matches_attribute(CSS::Selector::SimpleSelector::Attribute const& attribute, DOM::Element const& element)
{
if (attribute.match_type == CSS::Selector::SimpleSelector::Attribute::MatchType::HasAttribute) {
// Early way out in case of an attribute existence selector.
return element.has_attribute(attribute.name.to_string().to_deprecated_string());
}
auto const case_insensitive_match = (attribute.case_type == CSS::Selector::SimpleSelector::Attribute::CaseType::CaseInsensitiveMatch);
auto const case_sensitivity = case_insensitive_match
? CaseSensitivity::CaseInsensitive
: CaseSensitivity::CaseSensitive;
switch (attribute.match_type) {
case CSS::Selector::SimpleSelector::Attribute::MatchType::ExactValueMatch:
return case_insensitive_match
? Infra::is_ascii_case_insensitive_match(element.attribute(attribute.name.to_string().to_deprecated_string()), attribute.value)
: element.attribute(attribute.name.to_string().to_deprecated_string()) == attribute.value.to_deprecated_string();
case CSS::Selector::SimpleSelector::Attribute::MatchType::ContainsWord: {
if (attribute.value.is_empty()) {
// This selector is always false is match value is empty.
return false;
}
auto const view = element.attribute(attribute.name.to_string().to_deprecated_string()).split_view(' ');
auto const size = view.size();
for (size_t i = 0; i < size; ++i) {
auto const value = view.at(i);
if (case_insensitive_match
? Infra::is_ascii_case_insensitive_match(value, attribute.value)
: value == attribute.value) {
return true;
}
}
return false;
}
case CSS::Selector::SimpleSelector::Attribute::MatchType::ContainsString:
return !attribute.value.is_empty()
&& element.attribute(attribute.name.to_string().to_deprecated_string()).contains(attribute.value, case_sensitivity);
case CSS::Selector::SimpleSelector::Attribute::MatchType::StartsWithSegment: {
auto const element_attr_value = element.attribute(attribute.name.to_string().to_deprecated_string());
if (element_attr_value.is_empty()) {
// If the attribute value on element is empty, the selector is true
// if the match value is also empty and false otherwise.
return attribute.value.is_empty();
}
if (attribute.value.is_empty()) {
return false;
}
auto segments = element_attr_value.split_view('-');
return case_insensitive_match
? Infra::is_ascii_case_insensitive_match(segments.first(), attribute.value)
: segments.first() == attribute.value;
}
case CSS::Selector::SimpleSelector::Attribute::MatchType::StartsWithString:
return !attribute.value.is_empty()
&& element.attribute(attribute.name.to_string().to_deprecated_string()).starts_with(attribute.value, case_sensitivity);
case CSS::Selector::SimpleSelector::Attribute::MatchType::EndsWithString:
return !attribute.value.is_empty()
&& element.attribute(attribute.name.to_string().to_deprecated_string()).ends_with(attribute.value, case_sensitivity);
default:
break;
}
return false;
}
static inline DOM::Element const* previous_sibling_with_same_tag_name(DOM::Element const& element)
{
for (auto const* sibling = element.previous_element_sibling(); sibling; sibling = sibling->previous_element_sibling()) {
if (sibling->tag_name() == element.tag_name())
return sibling;
}
return nullptr;
}
static inline DOM::Element const* next_sibling_with_same_tag_name(DOM::Element const& element)
{
for (auto const* sibling = element.next_element_sibling(); sibling; sibling = sibling->next_element_sibling()) {
if (sibling->tag_name() == element.tag_name())
return sibling;
}
return nullptr;
}
static inline 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::Link:
return matches_link_pseudo_class(element);
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::FocusWithin: {
auto* focused_element = element.document().focused_element();
return focused_element && element.is_inclusive_ancestor_of(*focused_element);
}
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: {
if (!element.has_children())
return true;
if (element.first_child_of_type<DOM::Element>())
return false;
// NOTE: CSS Selectors level 4 changed ":empty" to also match whitespace-only text nodes.
// However, none of the major browser supports this yet, so let's just hang back until they do.
bool has_nonempty_text_child = false;
element.for_each_child_of_type<DOM::Text>([&](auto const& text_child) {
if (!text_child.data().is_empty()) {
has_nonempty_text_child = true;
return IterationDecision::Break;
}
return IterationDecision::Continue;
});
return !has_nonempty_text_child;
}
case CSS::Selector::SimpleSelector::PseudoClass::Type::Root:
return is<HTML::HTMLHtmlElement>(element);
case CSS::Selector::SimpleSelector::PseudoClass::Type::FirstOfType:
return !previous_sibling_with_same_tag_name(element);
case CSS::Selector::SimpleSelector::PseudoClass::Type::LastOfType:
return !next_sibling_with_same_tag_name(element);
case CSS::Selector::SimpleSelector::PseudoClass::Type::OnlyOfType:
return !previous_sibling_with_same_tag_name(element) && !next_sibling_with_same_tag_name(element);
case CSS::Selector::SimpleSelector::PseudoClass::Type::Lang:
return matches_lang_pseudo_class(element, pseudo_class.languages);
case CSS::Selector::SimpleSelector::PseudoClass::Type::Disabled:
// https://html.spec.whatwg.org/multipage/semantics-other.html#selector-disabled
// The :disabled pseudo-class must match any element that is actually disabled.
return element.is_actually_disabled();
case CSS::Selector::SimpleSelector::PseudoClass::Type::Enabled:
// https://html.spec.whatwg.org/multipage/semantics-other.html#selector-enabled
// The :enabled pseudo-class must match any button, input, select, textarea, optgroup, option, fieldset element, or form-associated custom element that is not actually disabled.
return (is<HTML::HTMLButtonElement>(element) || is<HTML::HTMLInputElement>(element) || is<HTML::HTMLSelectElement>(element) || is<HTML::HTMLTextAreaElement>(element) || is<HTML::HTMLOptGroupElement>(element) || is<HTML::HTMLOptionElement>(element) || is<HTML::HTMLFieldSetElement>(element))
&& !element.is_actually_disabled();
case CSS::Selector::SimpleSelector::PseudoClass::Type::Checked:
return matches_checked_pseudo_class(element);
case CSS::Selector::SimpleSelector::PseudoClass::Type::Is:
case CSS::Selector::SimpleSelector::PseudoClass::Type::Where:
for (auto& selector : pseudo_class.argument_selector_list) {
if (matches(selector, element))
return true;
}
return false;
case CSS::Selector::SimpleSelector::PseudoClass::Type::Not:
for (auto& selector : pseudo_class.argument_selector_list) {
if (matches(selector, element))
return false;
}
return true;
case CSS::Selector::SimpleSelector::PseudoClass::Type::NthChild:
case CSS::Selector::SimpleSelector::PseudoClass::Type::NthLastChild:
case CSS::Selector::SimpleSelector::PseudoClass::Type::NthOfType:
case CSS::Selector::SimpleSelector::PseudoClass::Type::NthLastOfType:
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;
auto matches_selector_list = [](CSS::SelectorList const& list, DOM::Element const& element) {
if (list.is_empty())
return true;
for (auto const& child_selector : list) {
if (matches(child_selector, element)) {
return true;
}
}
return false;
};
int index = 1;
switch (pseudo_class.type) {
case CSS::Selector::SimpleSelector::PseudoClass::Type::NthChild: {
if (!matches_selector_list(pseudo_class.argument_selector_list, element))
return false;
for (auto* child = parent->first_child_of_type<DOM::Element>(); child && child != &element; child = child->next_element_sibling()) {
if (matches_selector_list(pseudo_class.argument_selector_list, *child))
++index;
}
break;
}
case CSS::Selector::SimpleSelector::PseudoClass::Type::NthLastChild: {
if (!matches_selector_list(pseudo_class.argument_selector_list, element))
return false;
for (auto* child = parent->last_child_of_type<DOM::Element>(); child && child != &element; child = child->previous_element_sibling()) {
if (matches_selector_list(pseudo_class.argument_selector_list, *child))
++index;
}
break;
}
case CSS::Selector::SimpleSelector::PseudoClass::Type::NthOfType: {
for (auto* child = previous_sibling_with_same_tag_name(element); child; child = previous_sibling_with_same_tag_name(*child))
++index;
break;
}
case CSS::Selector::SimpleSelector::PseudoClass::Type::NthLastOfType: {
for (auto* child = next_sibling_with_same_tag_name(element); child; child = next_sibling_with_same_tag_name(*child))
++index;
break;
}
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 false;
}
static inline 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.name() == element.attribute(HTML::AttributeNames::id).view();
case CSS::Selector::SimpleSelector::Type::Class:
return element.has_class(component.name());
case CSS::Selector::SimpleSelector::Type::TagName:
// See https://html.spec.whatwg.org/multipage/semantics-other.html#case-sensitivity-of-selectors
if (element.document().document_type() == DOM::Document::Type::HTML)
return component.lowercase_name() == element.local_name().view();
return Infra::is_ascii_case_insensitive_match(component.name(), 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:
// Pseudo-element matching/not-matching is handled in the top level matches().
return true;
default:
VERIFY_NOT_REACHED();
}
}
static inline bool matches(CSS::Selector const& selector, int component_list_index, DOM::Element const& element)
{
auto& relative_selector = selector.compound_selectors()[component_list_index];
for (auto& simple_selector : relative_selector.simple_selectors) {
if (!matches(simple_selector, element))
return false;
}
switch (relative_selector.combinator) {
case CSS::Selector::Combinator::None:
return true;
case CSS::Selector::Combinator::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, static_cast<DOM::Element const&>(*ancestor)))
return true;
}
return false;
case CSS::Selector::Combinator::ImmediateChild:
VERIFY(component_list_index != 0);
if (!element.parent() || !is<DOM::Element>(*element.parent()))
return false;
return matches(selector, component_list_index - 1, static_cast<DOM::Element const&>(*element.parent()));
case CSS::Selector::Combinator::NextSibling:
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::Combinator::SubsequentSibling:
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::Combinator::Column:
TODO();
}
VERIFY_NOT_REACHED();
}
bool matches(CSS::Selector const& selector, DOM::Element const& element, Optional<CSS::Selector::PseudoElement> pseudo_element)
{
VERIFY(!selector.compound_selectors().is_empty());
if (pseudo_element.has_value() && selector.pseudo_element() != pseudo_element)
return false;
if (!pseudo_element.has_value() && selector.pseudo_element().has_value())
return false;
return matches(selector, selector.compound_selectors().size() - 1, element);
}
}
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