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12e8f503aa
This works by generating random values using XorShift128PlusRNG at compute time and then caching them on the document using the relevant random-caching-key
86 lines
3.5 KiB
C++
86 lines
3.5 KiB
C++
/*
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* Copyright (c) 2025, Callum Law <callumlaw1709@outlook.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "RandomValueSharingStyleValue.h"
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#include <LibWeb/CSS/StyleValues/CalculatedStyleValue.h>
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#include <LibWeb/CSS/StyleValues/NumberStyleValue.h>
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#include <LibWeb/DOM/Document.h>
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namespace Web::CSS {
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ValueComparingNonnullRefPtr<StyleValue const> RandomValueSharingStyleValue::absolutized(ComputationContext const& computation_context) const
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{
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// https://drafts.csswg.org/css-values-5/#random-caching
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// Each instance of a random function in styles has an associated random base value.
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// If the random function’s <random-value-sharing> is fixed <number>, the random base value is that number.
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if (m_fixed_value) {
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auto const& absolutized_fixed_value = m_fixed_value->absolutized(computation_context);
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if (m_fixed_value == absolutized_fixed_value)
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return *this;
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return RandomValueSharingStyleValue::create_fixed(absolutized_fixed_value);
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}
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// Otherwise, the random base value is a pseudo-random real number in the range `[0, 1)` (greater than or equal to 0
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// and less than 1), generated from a uniform distribution, and influenced by the function’s random caching key.
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// A random caching key is a tuple of:
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RandomCachingKey random_caching_key {
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// 1. A string name: the value of the <dashed-ident>, if specified in <random-value-sharing>; or else a string
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// of the form "PROPERTY N", where PROPERTY is the name of the property the random function is used in
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// (before shorthand expansion, if relevant), and N is the index of the random function among other random
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// functions in the same property value.
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.name = m_name.value(),
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// 2. An element ID identifying the element the style is being applied to, or null if element-shared is
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// specified in <random-value-sharing>.
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// FIXME: Use the pseudo element's unique_id() when that's accessible
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.element_id = m_element_shared ? Optional<UniqueNodeID> { OptionalNone {} } : Optional<UniqueNodeID> { computation_context.abstract_element->element().unique_id() },
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// 3. A document ID identifying the Document the styles are from.
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// NB: This is implicit since the cache is stored on the document or the element (which is a child of the document).
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};
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auto random_base_value = const_cast<DOM::Element&>(computation_context.abstract_element->element()).ensure_css_random_base_value(random_caching_key);
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return RandomValueSharingStyleValue::create_fixed(NumberStyleValue::create(random_base_value));
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}
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double RandomValueSharingStyleValue::random_base_value() const
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{
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VERIFY(m_fixed_value);
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VERIFY(m_fixed_value->is_number() || (m_fixed_value->is_calculated() && m_fixed_value->as_calculated().resolves_to_number()));
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if (m_fixed_value->is_number())
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return m_fixed_value->as_number().number();
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if (m_fixed_value->is_calculated())
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return m_fixed_value->as_calculated().resolve_number({}).value();
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VERIFY_NOT_REACHED();
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}
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String RandomValueSharingStyleValue::to_string(SerializationMode serialization_mode) const
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{
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if (m_fixed_value)
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return MUST(String::formatted("fixed {}", m_fixed_value->to_string(serialization_mode)));
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StringBuilder builder;
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if (!m_is_auto)
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builder.appendff("{}", m_name.value());
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if (m_element_shared) {
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if (!builder.is_empty())
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builder.append(' ');
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builder.append("element-shared"sv);
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}
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return builder.to_string_without_validation();
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}
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}
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