LibWeb: Move "visible in viewport" state tracking to ImageLoader

This should technically apply to any LayoutImage, so let's just move
it to ImageLoader.

Libraries/LibWeb/DOM/HTMLImageElement.cpp

@@ -87,9 +87,4 @@ const Gfx::Bitmap* HTMLImageElement::bitmap() const
     return m_image_loader.bitmap();
 }
 
-void HTMLImageElement::set_visible_in_viewport(Badge<LayoutDocument>, bool visible_in_viewport)
-{
-    m_image_loader.set_visible_in_viewport(visible_in_viewport);
-}
-
 }

Libraries/LibWeb/DOM/HTMLImageElement.h

@@ -51,8 +51,6 @@ public:
     const Gfx::Bitmap* bitmap() const;
     const Gfx::ImageDecoder* image_decoder() const;
 
-    void set_visible_in_viewport(Badge<LayoutDocument>, bool);
-
 private:
     void animate();
 

Libraries/LibWeb/Layout/LayoutDocument.cpp

@@ -71,8 +71,7 @@ void LayoutDocument::did_set_viewport_rect(Badge<Frame>, const Gfx::IntRect& a_v
 {
     Gfx::FloatRect viewport_rect(a_viewport_rect.x(), a_viewport_rect.y(), a_viewport_rect.width(), a_viewport_rect.height());
     for_each_in_subtree_of_type<LayoutImage>([&](auto& layout_image) {
-        if (is<HTMLImageElement>(layout_image.node()))
-            const_cast<HTMLImageElement&>(to<HTMLImageElement>(layout_image.node())).set_visible_in_viewport({}, viewport_rect.intersects(layout_image.absolute_rect()));
+        const_cast<LayoutImage&>(layout_image).set_visible_in_viewport({}, viewport_rect.intersects(layout_image.absolute_rect()));
         return IterationDecision::Continue;
     });
 }

Libraries/LibWeb/Layout/LayoutImage.cpp

@@ -108,4 +108,9 @@ bool LayoutImage::renders_as_alt_text() const
     return false;
 }
 
+void LayoutImage::set_visible_in_viewport(Badge<LayoutDocument>, bool visible_in_viewport)
+{
+    m_image_loader.set_visible_in_viewport(visible_in_viewport);
+}
+
 }

Libraries/LibWeb/Layout/LayoutImage.h

@@ -45,6 +45,8 @@ public:
 
     bool renders_as_alt_text() const;
 
+    void set_visible_in_viewport(Badge<LayoutDocument>, bool);
+
 private:
     virtual const char* class_name() const override { return "LayoutImage"; }
     virtual bool is_image() const override { return true; }

Libraries/LibWeb/Loader/ImageLoader.cpp

@@ -44,7 +44,7 @@ void ImageLoader::load(const URL& url)
     set_resource(ResourceLoader::the().load_resource(Resource::Type::Image, request));
 }
 
-void ImageLoader::set_visible_in_viewport(bool visible_in_viewport)
+void ImageLoader::set_visible_in_viewport(bool visible_in_viewport) const
 {
     if (m_visible_in_viewport == visible_in_viewport)
         return;
@@ -54,7 +54,7 @@ void ImageLoader::set_visible_in_viewport(bool visible_in_viewport)
     //        the whole document, updating "is visible in viewport" flags, and this could lead
     //        to the same bitmap being marked volatile back and forth unnecessarily.
     if (resource())
-        resource()->update_volatility();
+        const_cast<ImageResource*>(resource())->update_volatility();
 }
 
 void ImageLoader::resource_did_load()

Libraries/LibWeb/Loader/ImageLoader.h

@@ -41,7 +41,7 @@ public:
     const Gfx::Bitmap* bitmap() const;
     const Gfx::ImageDecoder* image_decoder() const;
 
-    void set_visible_in_viewport(bool);
+    void set_visible_in_viewport(bool) const;
 
     Function<void()> on_load;
     Function<void()> on_fail;
@@ -57,7 +57,7 @@ private:
     void animate();
 
     RefPtr<Gfx::ImageDecoder> m_decoder;
-    bool m_visible_in_viewport { false };
+    mutable bool m_visible_in_viewport { false };
 
     size_t m_current_frame_index { 0 };
     size_t m_loops_completed { 0 };