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LibWeb: Improve support for selecting an image source

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Apply media conditions before selecting a size and add an algorithm to
select an image source based on pixel density.
This commit is contained in:
Andi Gallo 2023-05-28 02:04:58 +00:00 • committed by Andreas Kling
parent 29d29134ba
commit c411b5408e
2 changed files with 43 additions and 11 deletions
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42
Userland/Libraries/LibWeb/HTML/SourceSet.cpp
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@ -5,6 +5,8 @@
*/
#include <AK/Function.h>
#include <AK/HashMap.h>
#include <AK/QuickSort.h>
#include <LibWeb/Bindings/MainThreadVM.h>
#include <LibWeb/CSS/Parser/Parser.h>
#include <LibWeb/HTML/SourceSet.h>
@ -22,19 +24,43 @@ bool SourceSet::is_empty() const
return m_sources.is_empty();
}
static double pixel_density(ImageSource const& image_source)
{
return image_source.descriptor.get<ImageSource::PixelDensityDescriptorValue>().value;
}
// https://html.spec.whatwg.org/multipage/images.html#select-an-image-source-from-a-source-set
ImageSourceAndPixelDensity SourceSet::select_an_image_source()
{
// FIXME: 1. If an entry b in sourceSet has the same associated pixel density descriptor as an earlier entry a in sourceSet,
// then remove entry b.
// Repeat this step until none of the entries in sourceSet have the same associated pixel density descriptor
// as an earlier entry.
// 1. If an entry b in sourceSet has the same associated pixel density descriptor as an earlier entry a in sourceSet,
// then remove entry b.
// Repeat this step until none of the entries in sourceSet have the same associated pixel density descriptor
// as an earlier entry.
// FIXME: 2. In an implementation-defined manner, choose one image source from sourceSet. Let this be selectedSource.
Vector<ImageSource> unique_pixel_density_sources;
HashMap<double, ImageSource> unique_pixel_density_sources_map;
for (auto const& source : m_sources) {
auto source_pixel_density = pixel_density(source);
if (!unique_pixel_density_sources_map.contains(source_pixel_density)) {
unique_pixel_density_sources.append(source);
unique_pixel_density_sources_map.set(source_pixel_density, source);
}
}
// FIXME: 3. Return selectedSource and its associated pixel density.
// 2. In an implementation-defined manner, choose one image source from sourceSet. Let this be selectedSource.
// In our case, select the lowest density greater than 1, otherwise the greatest density available.
// 3. Return selectedSource and its associated pixel density.
return { m_sources.first(), 1.0f };
quick_sort(unique_pixel_density_sources, [](auto& a, auto& b) {
return pixel_density(a) < pixel_density(b);
});
for (auto const& source : unique_pixel_density_sources) {
if (pixel_density(source) >= 1) {
return { source, pixel_density(source) };
}
}
return { unique_pixel_density_sources.last(), pixel_density(unique_pixel_density_sources.last()) };
}
static StringView collect_a_sequence_of_code_points(Function<bool(u32 code_point)> condition, StringView input, size_t& position)
@ -328,7 +354,7 @@ SourceSet SourceSet::create(DOM::Document const& document, String default_source
source_set = parse_a_srcset_attribute(srcset);
// 3. Let source size be the result of parsing sizes.
auto source_size = parse_a_sizes_attribute(document, sizes);
source_set.m_source_size = parse_a_sizes_attribute(document, sizes);
// 4. If default source is not the empty string and source set does not contain an image source
// with a pixel density descriptor value of 1, and no image source with a width descriptor,