LibWeb: Add ViewportPaintable to represent viewports in the paint tree

This patch just adds the new root paintable and updates the tests
expectations. The next patch will move painting logic from the layout
viewport to the paint viewport.

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -493,6 +493,7 @@ set(SOURCES
     Painting/TableBordersPainting.cpp
     Painting/TextPaintable.cpp
     Painting/VideoPaintable.cpp
+    Painting/ViewportPaintable.cpp
     PerformanceTimeline/EntryTypes.cpp
     PerformanceTimeline/PerformanceEntry.cpp
     PermissionsPolicy/AutoplayAllowlist.cpp

Userland/Libraries/LibWeb/Layout/Viewport.cpp

@@ -9,6 +9,7 @@
 #include <LibWeb/Layout/Viewport.h>
 #include <LibWeb/Painting/PaintableBox.h>
 #include <LibWeb/Painting/StackingContext.h>
+#include <LibWeb/Painting/ViewportPaintable.h>
 
 namespace Web::Layout {
 
@@ -126,4 +127,9 @@ void Viewport::recompute_selection_states()
     }
 }
 
+JS::GCPtr<Painting::Paintable> Viewport::create_paintable() const
+{
+    return Painting::ViewportPaintable::create(*this);
+}
+
 }

Userland/Libraries/LibWeb/Layout/Viewport.h

@@ -29,6 +29,8 @@ public:
     void recompute_selection_states();
 
 private:
+    virtual JS::GCPtr<Painting::Paintable> create_paintable() const override;
+
     void build_stacking_context_tree();
     virtual bool is_viewport() const override { return true; }
 };

Userland/Libraries/LibWeb/Painting/PaintableBox.h

@@ -218,7 +218,7 @@ private:
     Optional<TableCellCoordinates> m_table_cell_coordinates;
 };
 
-class PaintableWithLines final : public PaintableBox {
+class PaintableWithLines : public PaintableBox {
     JS_CELL(PaintableWithLines, PaintableBox);
 
 public:

Userland/Libraries/LibWeb/Painting/ViewportPaintable.cpp

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2023, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Layout/Viewport.h>
+#include <LibWeb/Painting/ViewportPaintable.h>
+
+namespace Web::Painting {
+
+JS::NonnullGCPtr<ViewportPaintable> ViewportPaintable::create(Layout::Viewport const& layout_viewport)
+{
+    return layout_viewport.heap().allocate_without_realm<ViewportPaintable>(layout_viewport);
+}
+
+ViewportPaintable::ViewportPaintable(Layout::Viewport const& layout_viewport)
+    : PaintableWithLines(layout_viewport)
+{
+}
+
+ViewportPaintable::~ViewportPaintable() = default;
+
+}

Userland/Libraries/LibWeb/Painting/ViewportPaintable.h

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2023, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/Painting/PaintableBox.h>
+
+namespace Web::Painting {
+
+class ViewportPaintable final : public PaintableWithLines {
+    JS_CELL(ViewportPaintable, PaintableWithLines);
+
+public:
+    static JS::NonnullGCPtr<ViewportPaintable> create(Layout::Viewport const&);
+    virtual ~ViewportPaintable() override;
+
+private:
+    explicit ViewportPaintable(Layout::Viewport const&);
+};
+
+}