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54 lines
3.1 KiB
C++
54 lines
3.1 KiB
C++
/*
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* Copyright (c) 2022, MacDue <macdue@dueutil.tech>
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* Copyright (c) 2024, Sam Atkins <sam@ladybird.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "Sizing.h"
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namespace Web::CSS {
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// https://drafts.csswg.org/css-images/#default-sizing
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CSSPixelSize run_default_sizing_algorithm(
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Optional<CSSPixels> specified_width, Optional<CSSPixels> specified_height,
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Optional<CSSPixels> natural_width, Optional<CSSPixels> natural_height,
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Optional<CSSPixelFraction> natural_aspect_ratio,
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CSSPixelSize default_size)
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{
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// If the specified size is a definite width and height, the concrete object size is given that width and height.
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if (specified_width.has_value() && specified_height.has_value())
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return CSSPixelSize { specified_width.value(), specified_height.value() };
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// If the specified size is only a width or height (but not both) then the concrete object size is given that specified width or height.
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// The other dimension is calculated as follows:
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if (specified_width.has_value() || specified_height.has_value()) {
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// 1. If the object has a natural aspect ratio,
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// the missing dimension of the concrete object size is calculated using that aspect ratio and the present dimension.
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if (natural_aspect_ratio.has_value() && !natural_aspect_ratio->might_be_saturated()) {
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if (specified_width.has_value())
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return CSSPixelSize { specified_width.value(), (CSSPixels(1) / natural_aspect_ratio.value()) * specified_width.value() };
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if (specified_height.has_value())
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return CSSPixelSize { specified_height.value() * natural_aspect_ratio.value(), specified_height.value() };
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}
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// 2. Otherwise, if the missing dimension is present in the object’s natural dimensions,
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// the missing dimension is taken from the object’s natural dimensions.
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if (specified_height.has_value() && natural_width.has_value())
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return CSSPixelSize { natural_width.value(), specified_height.value() };
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if (specified_width.has_value() && natural_height.has_value())
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return CSSPixelSize { specified_width.value(), natural_height.value() };
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// 3. Otherwise, the missing dimension of the concrete object size is taken from the default object size.
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if (specified_height.has_value())
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return CSSPixelSize { default_size.width(), specified_height.value() };
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if (specified_width.has_value())
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return CSSPixelSize { specified_width.value(), default_size.height() };
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VERIFY_NOT_REACHED();
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}
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// If the specified size has no constraints:
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// 1. If the object has a natural height or width, its size is resolved as if its natural dimensions were given as the specified size.
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if (natural_width.has_value() || natural_height.has_value())
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return run_default_sizing_algorithm(natural_width, natural_height, natural_width, natural_height, natural_aspect_ratio, default_size);
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// FIXME: 2. Otherwise, its size is resolved as a contain constraint against the default object size.
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return default_size;
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}
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}
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