LibWeb: Start fleshing out HTML "image requests" and "image data"

This patch adds HTML::ImageRequest and HTML::DecodedImageData.

The latter had to use a different name than "ImageData", as there is
already an IDL-exposed ImageData class in HTML.

Userland/Libraries/LibWeb/HTML/ImageRequest.h

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2023, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Error.h>
+#include <AK/OwnPtr.h>
+#include <AK/URL.h>
+#include <LibGfx/Size.h>
+#include <LibJS/Heap/Handle.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::HTML {
+
+// https://html.spec.whatwg.org/multipage/images.html#image-request
+class ImageRequest : public RefCounted<ImageRequest> {
+public:
+    static ErrorOr<NonnullRefPtr<ImageRequest>> create();
+    ~ImageRequest();
+
+    // https://html.spec.whatwg.org/multipage/images.html#img-req-state
+    enum class State {
+        Unavailable,
+        PartiallyAvailable,
+        CompletelyAvailable,
+        Broken,
+    };
+
+    bool is_available() const;
+
+    State state() const;
+    void set_state(State);
+
+    AK::URL const& current_url() const;
+    void set_current_url(AK::URL);
+
+    // https://html.spec.whatwg.org/multipage/images.html#abort-the-image-request
+    void abort(JS::Realm&);
+
+    [[nodiscard]] RefPtr<DecodedImageData const> image_data() const;
+    void set_image_data(RefPtr<DecodedImageData const>);
+
+    [[nodiscard]] float current_pixel_density() const { return m_current_pixel_density; }
+    void set_current_pixel_density(float density) { m_current_pixel_density = density; }
+
+    [[nodiscard]] Optional<Gfx::FloatSize> const& preferred_density_corrected_dimensions() const { return m_preferred_density_corrected_dimensions; }
+    void set_preferred_density_corrected_dimensions(Optional<Gfx::FloatSize> dimensions) { m_preferred_density_corrected_dimensions = move(dimensions); }
+
+    // https://html.spec.whatwg.org/multipage/images.html#prepare-an-image-for-presentation
+    void prepare_for_presentation(HTMLImageElement&);
+
+    void set_fetch_controller(JS::GCPtr<Fetch::Infrastructure::FetchController>);
+
+private:
+    ImageRequest();
+
+    // https://html.spec.whatwg.org/multipage/images.html#img-req-state
+    // An image request's state is initially unavailable.
+    State m_state { State::Unavailable };
+
+    // https://html.spec.whatwg.org/multipage/images.html#img-req-url
+    // An image request's current URL is initially the empty string.
+    AK::URL m_current_url;
+
+    // https://html.spec.whatwg.org/multipage/images.html#img-req-data
+    RefPtr<DecodedImageData const> m_image_data;
+
+    // https://html.spec.whatwg.org/multipage/images.html#current-pixel-density
+    // Each image request has a current pixel density, which must initially be 1.
+    float m_current_pixel_density { 1 };
+
+    // https://html.spec.whatwg.org/multipage/images.html#preferred-density-corrected-dimensions
+    // Each image request has preferred density-corrected dimensions,
+    // which is either a struct consisting of a width and a height or is null. It must initially be null.
+    Optional<Gfx::FloatSize> m_preferred_density_corrected_dimensions;
+
+    JS::Handle<Fetch::Infrastructure::FetchController> m_fetch_controller;
+};
+
+}