LibWeb+WebContent: Move paint recording init into Navigable

This refactoring makes WebContent less aware of LibWeb internals.
The code that initializes paint recording commands now resides in
`Navigable::paint()`. Additionally, we no longer need to reuse
PaintContext across iframes, allowing us to avoid saving and restoring
its state before recursing into an iframe.

Userland/Libraries/LibWeb/HTML/Navigable.cpp

@@ -32,6 +32,7 @@
 #include <LibWeb/Loader/GeneratedPagesLoader.h>
 #include <LibWeb/Page/Page.h>
 #include <LibWeb/Painting/Paintable.h>
+#include <LibWeb/Painting/ViewportPaintable.h>
 #include <LibWeb/Platform/EventLoopPlugin.h>
 #include <LibWeb/XHR/FormData.h>
 
@@ -2032,4 +2033,45 @@ void Navigable::inform_the_navigation_api_about_aborting_navigation()
     });
 }
 
+void Navigable::paint(Painting::RecordingPainter& recording_painter, PaintConfig config)
+{
+    auto document = active_document();
+    if (!document)
+        return;
+
+    auto const& page = traversable_navigable()->page();
+    auto viewport_rect = page.css_to_device_rect(this->viewport_rect());
+    Gfx::IntRect bitmap_rect { {}, viewport_rect.size().to_type<int>() };
+
+    document->update_layout();
+    auto background_color = document->background_color();
+
+    recording_painter.fill_rect(bitmap_rect, background_color);
+    if (!document->paintable())
+        return;
+
+    Web::PaintContext context(recording_painter, page.palette(), page.client().device_pixels_per_css_pixel());
+    context.set_device_viewport_rect(viewport_rect);
+    context.set_should_show_line_box_borders(config.should_show_line_box_borders);
+    context.set_should_paint_overlay(config.paint_overlay);
+    context.set_has_focus(config.has_focus);
+
+    if (is_traversable()) {
+        document->paintable()->collect_scroll_frames(context);
+    }
+
+    document->paintable()->paint_all_phases(context);
+
+    // FIXME: Support scrollable frames inside iframes.
+    if (is_traversable()) {
+        Vector<Gfx::IntPoint> scroll_offsets_by_frame_id;
+        scroll_offsets_by_frame_id.resize(context.scroll_frames().size());
+        for (auto [_, scrollable_frame] : context.scroll_frames())
+            scroll_offsets_by_frame_id[scrollable_frame.id] = context.rounded_device_point(
+                                                                         scrollable_frame.offset)
+                                                                  .to_type<int>();
+        recording_painter.apply_scroll_offsets(scroll_offsets_by_frame_id);
+    }
+}
+
 }

Userland/Libraries/LibWeb/HTML/Navigable.h

@@ -170,6 +170,13 @@ public:
 
     [[nodiscard]] TargetSnapshotParams snapshot_target_snapshot_params();
 
+    struct PaintConfig {
+        bool paint_overlay { false };
+        bool should_show_line_box_borders { false };
+        bool has_focus { false };
+    };
+    void paint(Painting::RecordingPainter&, PaintConfig);
+
 protected:
     Navigable();
 

Userland/Libraries/LibWeb/Painting/NestedBrowsingContextPaintable.cpp

@@ -41,25 +41,25 @@ void NestedBrowsingContextPaintable::paint(PaintContext& context, PaintPhase pha
         auto clip_rect = context.rounded_device_rect(absolute_rect);
         ScopedCornerRadiusClip corner_clip { context, clip_rect, normalized_border_radii_data(ShrinkRadiiForBorders::Yes) };
 
-        auto* hosted_document = layout_box().dom_node().content_document_without_origin_check();
+        auto const* hosted_document = layout_box().dom_node().content_document_without_origin_check();
         if (!hosted_document)
             return;
-        auto* hosted_paint_tree = hosted_document->paintable();
+        auto const* hosted_paint_tree = hosted_document->paintable();
         if (!hosted_paint_tree)
             return;
 
         context.recording_painter().save();
-        auto old_viewport_rect = context.device_viewport_rect();
 
         context.recording_painter().add_clip_rect(clip_rect.to_type<int>());
-
         auto absolute_device_rect = context.enclosing_device_rect(absolute_rect);
         context.recording_painter().translate(absolute_device_rect.x().value(), absolute_device_rect.y().value());
 
-        context.set_device_viewport_rect({ {}, context.enclosing_device_size(layout_box().dom_node().content_navigable()->size()) });
-        const_cast<ViewportPaintable*>(hosted_paint_tree)->paint_all_phases(context);
+        HTML::Navigable::PaintConfig paint_config;
+        paint_config.paint_overlay = context.should_paint_overlay();
+        paint_config.should_show_line_box_borders = context.should_show_line_box_borders();
+        paint_config.has_focus = context.has_focus();
+        const_cast<DOM::Document*>(hosted_document)->navigable()->paint(context.recording_painter(), paint_config);
 
-        context.set_device_viewport_rect(old_viewport_rect);
         context.recording_painter().restore();
 
         if constexpr (HIGHLIGHT_FOCUSED_FRAME_DEBUG) {