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a79ec6c228
We also resolve font-relative lengths based on the canvas' font, see the AD-HOC comment in AbstractCanvasMixin.cpp
55 lines
2.4 KiB
C++
55 lines
2.4 KiB
C++
/*
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* Copyright (c) 2026, 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 "AbstractCanvasMixin.h"
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#include <LibWeb/CSS/Parser/Parser.h>
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#include <LibWeb/CSS/ValueType.h>
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#include <LibWeb/DOM/Document.h>
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namespace Web::HTML {
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// https://drafts.csswg.org/css-color-4/#parse-a-css-color-value
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Optional<Color> AbstractCanvasMixin::parse_a_css_color_value(StringView const& value) const
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{
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// To parse a CSS <color> value, given a string input, and an optional context element element:
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// 1. Parse input as a <color>. If the result is failure, return failure; otherwise, let color be the result.
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auto color = parse_css_type(CSS::Parser::ParsingParams { CSS::Parser::SpecialContext::CanvasContextGenericValue }, value, CSS::ValueType::Color);
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if (!color)
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return {};
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// 2. Let used color be the result of resolving color to a used color. If the value of other properties on the
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// element a <color> is on is required to do the resolution (such as resolving a currentcolor or system color),
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// use element if it was passed, or the initial values of the properties if not.
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// AD-HOC: The spec tells us to use the element's properties as context but doesn't tell us how to resolve other
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// context dependent values (e.g. viewport relative lengths). This also differs from how font-relative
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// lengths are absolutized (i.e. using the canvas' font rather than the element's) in other canvas values
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// (e.g. letterSpacing) so we instead use a computation context based on the drawing state. See
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// https://github.com/whatwg/html/issues/12505.
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auto computation_context = computation_context_for_drawing_state();
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auto color_resolution_context = canvas_element().visit(
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[&](GC::Ref<HTMLCanvasElement> const& canvas_element) {
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canvas_element->document().update_style_if_needed_for_element(*canvas_element);
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if (canvas_element->computed_properties())
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return CSS::ColorResolutionContext::for_element(*canvas_element);
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return CSS::ColorResolutionContext {};
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},
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[&](GC::Ref<OffscreenCanvas> const&) {
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return CSS::ColorResolutionContext {};
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});
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auto used_color = color->absolutized(computation_context)->to_color(color_resolution_context).value();
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// 3. Return used color.
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return used_color;
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}
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}
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