From 18fa662eb2183a16e5abfd110540ba0d47f5e53a Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Tue, 15 Oct 2019 21:53:08 +0200
Subject: [PATCH] LibHTML: Use ImageLoader for <img> elements to defer bitmap
 decoding

We now wait until the pixels are actually needed before fully decoding
images in <img> elements.

This needs some more work and is currently a bit memory-wasteful since
we'll hang on to the raw image data forever.
---
 Libraries/LibHTML/DOM/HTMLImageElement.cpp | 15 +++++++++------
 Libraries/LibHTML/DOM/HTMLImageElement.h   |  4 ++++
 Libraries/LibHTML/Layout/LayoutImage.cpp   |  6 +++++-
 3 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/Libraries/LibHTML/DOM/HTMLImageElement.cpp b/Libraries/LibHTML/DOM/HTMLImageElement.cpp
index 2b34659a46..3ae099290b 100644
--- a/Libraries/LibHTML/DOM/HTMLImageElement.cpp
+++ b/Libraries/LibHTML/DOM/HTMLImageElement.cpp
@@ -29,7 +29,8 @@ void HTMLImageElement::load_image(const String& src)
             return;
         }
 
-        m_bitmap = load_png_from_memory(data.data(), data.size());
+        m_image_data = data;
+        m_image_loader = ImageLoader::create(m_image_data.data(), m_image_data.size());
         document().update_layout();
     });
 }
@@ -41,8 +42,8 @@ int HTMLImageElement::preferred_width() const
     if (ok)
         return width;
 
-    if (m_bitmap)
-        return m_bitmap->width();
+    if (m_image_loader)
+        return m_image_loader->width();
 
     return 0;
 }
@@ -54,8 +55,8 @@ int HTMLImageElement::preferred_height() const
     if (ok)
         return height;
 
-    if (m_bitmap)
-        return m_bitmap->height();
+    if (m_image_loader)
+        return m_image_loader->height();
 
     return 0;
 }
@@ -71,5 +72,7 @@ RefPtr<LayoutNode> HTMLImageElement::create_layout_node(const StyleProperties* p
 
 const GraphicsBitmap* HTMLImageElement::bitmap() const
 {
-    return m_bitmap;
+    if (!m_image_loader)
+        return nullptr;
+    return m_image_loader->bitmap();
 }
diff --git a/Libraries/LibHTML/DOM/HTMLImageElement.h b/Libraries/LibHTML/DOM/HTMLImageElement.h
index d9091fb052..04d265ed11 100644
--- a/Libraries/LibHTML/DOM/HTMLImageElement.h
+++ b/Libraries/LibHTML/DOM/HTMLImageElement.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <LibDraw/GraphicsBitmap.h>
+#include <LibDraw/ImageLoader.h>
 #include <LibHTML/DOM/HTMLElement.h>
 
 class HTMLImageElement : public HTMLElement {
@@ -16,11 +17,14 @@ public:
     int preferred_height() const;
 
     const GraphicsBitmap* bitmap() const;
+    const ImageLoader* image_loader() const { return m_image_loader; }
 
 private:
     void load_image(const String& src);
 
     virtual RefPtr<LayoutNode> create_layout_node(const StyleProperties* parent_style) const override;
 
+    RefPtr<ImageLoader> m_image_loader;
     mutable RefPtr<GraphicsBitmap> m_bitmap;
+    ByteBuffer m_image_data;
 };
diff --git a/Libraries/LibHTML/Layout/LayoutImage.cpp b/Libraries/LibHTML/Layout/LayoutImage.cpp
index 72a03f03cb..f25da78db5 100644
--- a/Libraries/LibHTML/Layout/LayoutImage.cpp
+++ b/Libraries/LibHTML/Layout/LayoutImage.cpp
@@ -37,6 +37,10 @@ void LayoutImage::render(RenderingContext& context)
     if (!is_visible())
         return;
 
+    // FIXME: This should be done at a different level. Also rect() does not include padding etc!
+    if (!context.viewport_rect().intersects(rect()))
+        return;
+
     if (renders_as_alt_text()) {
         context.painter().set_font(Font::default_font());
         StylePainter::paint_frame(context.painter(), rect(), FrameShape::Container, FrameShadow::Sunken, 2);
@@ -52,5 +56,5 @@ void LayoutImage::render(RenderingContext& context)
 
 bool LayoutImage::renders_as_alt_text() const
 {
-    return !node().bitmap();
+    return !node().image_loader();
 }