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LibWeb: Move our "default sizing algorithm" function into a public place

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Specifically, this is used by the updated algorithm for parsing a sizes
attribute, so we need access to it there.

No behaviour changes.
This commit is contained in:
Sam Atkins 2024-09-09 17:16:25 +01:00 • committed by Andreas Kling
commit 2671820ace
Notes: github-actions[bot] 2024-09-12 05:40:20 +00:00
5 changed files with 78 additions and 43 deletions
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54
Userland/Libraries/LibWeb/CSS/Sizing.cpp Normal file
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/*
* Copyright (c) 2022, MacDue <macdue@dueutil.tech>
* Copyright (c) 2024, Sam Atkins <sam@ladybird.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include "Sizing.h"
namespace Web::CSS {
// https://drafts.csswg.org/css-images/#default-sizing
CSSPixelSize run_default_sizing_algorithm(
Optional<CSSPixels> specified_width, Optional<CSSPixels> specified_height,
Optional<CSSPixels> natural_width, Optional<CSSPixels> natural_height,
Optional<CSSPixelFraction> natural_aspect_ratio,
CSSPixelSize default_size)
{
// If the specified size is a definite width and height, the concrete object size is given that width and height.
if (specified_width.has_value() && specified_height.has_value())
return CSSPixelSize { specified_width.value(), specified_height.value() };
// 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.
// The other dimension is calculated as follows:
if (specified_width.has_value() || specified_height.has_value()) {
// 1. If the object has a natural aspect ratio,
// the missing dimension of the concrete object size is calculated using that aspect ratio and the present dimension.
if (natural_aspect_ratio.has_value() && !natural_aspect_ratio->might_be_saturated()) {
if (specified_width.has_value())
return CSSPixelSize { specified_width.value(), (CSSPixels(1) / natural_aspect_ratio.value()) * specified_width.value() };
if (specified_height.has_value())
return CSSPixelSize { specified_height.value() * natural_aspect_ratio.value(), specified_height.value() };
}
// 2. Otherwise, if the missing dimension is present in the object’s natural dimensions,
// the missing dimension is taken from the object’s natural dimensions.
if (specified_height.has_value() && natural_width.has_value())
return CSSPixelSize { natural_width.value(), specified_height.value() };
if (specified_width.has_value() && natural_height.has_value())
return CSSPixelSize { specified_width.value(), natural_height.value() };
// 3. Otherwise, the missing dimension of the concrete object size is taken from the default object size.
if (specified_height.has_value())
return CSSPixelSize { default_size.width(), specified_height.value() };
if (specified_width.has_value())
return CSSPixelSize { specified_width.value(), default_size.height() };
VERIFY_NOT_REACHED();
}
// If the specified size has no constraints:
// 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.
if (natural_width.has_value() || natural_height.has_value())
return run_default_sizing_algorithm(natural_width, natural_height, natural_width, natural_height, natural_aspect_ratio, default_size);
// FIXME: 2. Otherwise, its size is resolved as a contain constraint against the default object size.
return default_size;
}
}