LibWeb: Let subframes propagate paint invalidations via host element

When a paint invalidation occurs inside a subframe, it bubbles up to
Frame::set_needs_display(). From there, we call PageView if this is
the main frame, or otherwise invalidate the subframe host element.

Libraries/LibWeb/DOM/HTMLIFrameElement.cpp

@@ -79,11 +79,6 @@ void HTMLIFrameElement::load_src(const String& value)
         return;
     }
 
-    m_hosted_frame->on_set_needs_display = [this](auto&) {
-        if (layout_node())
-            layout_node()->set_needs_display();
-    };
-
     m_hosted_frame->loader().load(url);
 }
 

Libraries/LibWeb/Frame/Frame.cpp

@@ -93,9 +93,14 @@ void Frame::set_needs_display(const Gfx::Rect& rect)
     if (!m_viewport_rect.intersects(rect))
         return;
 
-    if (!on_set_needs_display)
+    if (is_main_frame()) {
+        if (page_view())
+            page_view()->notify_needs_display({}, *this, rect);
         return;
-    on_set_needs_display(rect);
+    }
+
+    if (host_element() && host_element()->layout_node())
+        host_element()->layout_node()->set_needs_display();
 }
 
 void Frame::did_scroll(Badge<PageView>)

Libraries/LibWeb/Frame/Frame.h

@@ -60,7 +60,6 @@ public:
 
     void set_needs_display(const Gfx::Rect&);
 
-    Function<void(const Gfx::Rect&)> on_set_needs_display;
     Function<void(const String&)> on_title_change;
     Function<void(const URL&)> on_load_start;
     Function<void(const Gfx::Bitmap&)> on_favicon_change;

Libraries/LibWeb/PageView.cpp

@@ -72,15 +72,6 @@ PageView::PageView()
         if (on_load_start)
             on_load_start(url);
     };
-    main_frame().on_set_needs_display = [this](auto& content_rect) {
-        if (content_rect.is_empty()) {
-            update();
-            return;
-        }
-        Gfx::Rect adjusted_rect = content_rect;
-        adjusted_rect.set_location(to_widget_position(content_rect.location()));
-        update(adjusted_rect);
-    };
 
     set_should_hide_unnecessary_scrollbars(true);
     set_background_role(ColorRole::Base);
@@ -334,6 +325,22 @@ Gfx::Point PageView::to_screen_position(const Web::Frame& frame, const Gfx::Poin
     return screen_relative_rect().location().translated(offset).translated(frame_position);
 }
 
+Gfx::Rect PageView::to_widget_rect(const Web::Frame& frame, const Gfx::Rect& frame_rect) const
+{
+    Gfx::Point offset;
+    for (auto* f = &frame; f; f = f->parent()) {
+        if (!f->host_element())
+            return {};
+        if (!f->host_element()->layout_node())
+            return {};
+        auto f_position = f->host_element()->layout_node()->box_type_agnostic_position().to_int_point();
+        offset.move_by(f_position);
+    }
+
+    auto content_position = frame_rect.location().translated(offset);
+    return { to_widget_position(content_position), frame_rect.size() };
+}
+
 void PageView::notify_link_context_menu_request(Badge<EventHandler>, Web::Frame& frame, const Gfx::Point& content_position, const String& href, const String&, unsigned)
 {
     if (on_link_context_menu_request)
@@ -356,4 +363,9 @@ void PageView::notify_tooltip_area_leave(Badge<EventHandler>, Web::Frame&)
     GUI::Application::the().hide_tooltip();
 }
 
+void PageView::notify_needs_display(Badge<Web::Frame>, Web::Frame& frame, const Gfx::Rect& rect)
+{
+    update(to_widget_rect(frame, rect));
+}
+
 }

Libraries/LibWeb/PageView.h

@@ -81,6 +81,7 @@ public:
     void notify_link_hover(Badge<EventHandler>, Web::Frame&, const String& href);
     void notify_tooltip_area_enter(Badge<EventHandler>, Web::Frame&, const Gfx::Point& content_position, const String& title);
     void notify_tooltip_area_leave(Badge<EventHandler>, Web::Frame&);
+    void notify_needs_display(Badge<Web::Frame>, Web::Frame&, const Gfx::Rect&);
 
 protected:
     PageView();
@@ -97,6 +98,7 @@ private:
     virtual void did_scroll() override;
 
     Gfx::Point to_screen_position(const Web::Frame&, const Gfx::Point&) const;
+    Gfx::Rect to_widget_rect(const Web::Frame&, const Gfx::Rect&) const;
 
     void layout_and_sync_size();