LibWeb: Rename Web::Frame to Web::BrowsingContext

Our "frame" concept very closely matches what the web specs call a
"browsing context", so let's rename it to that. :^)

The "main frame" becomes the "top-level browsing context",
and "sub-frames" are now "nested browsing contexts".

Userland/Libraries/LibWeb/Page/BrowsingContext.h

@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/Noncopyable.h>
+#include <AK/RefPtr.h>
+#include <AK/WeakPtr.h>
+#include <LibCore/Timer.h>
+#include <LibGfx/Bitmap.h>
+#include <LibGfx/Rect.h>
+#include <LibGfx/Size.h>
+#include <LibWeb/DOM/Position.h>
+#include <LibWeb/Loader/FrameLoader.h>
+#include <LibWeb/Page/EventHandler.h>
+#include <LibWeb/TreeNode.h>
+
+namespace Web {
+
+class BrowsingContext : public TreeNode<BrowsingContext> {
+public:
+    static NonnullRefPtr<BrowsingContext> create_nested(DOM::Element& host_element, BrowsingContext& top_level_browsing_context) { return adopt_ref(*new BrowsingContext(host_element, top_level_browsing_context)); }
+    static NonnullRefPtr<BrowsingContext> create(Page& page) { return adopt_ref(*new BrowsingContext(page)); }
+    ~BrowsingContext();
+
+    class ViewportClient {
+    public:
+        virtual ~ViewportClient() { }
+        virtual void frame_did_set_viewport_rect(const Gfx::IntRect&) = 0;
+    };
+    void register_viewport_client(ViewportClient&);
+    void unregister_viewport_client(ViewportClient&);
+
+    bool is_top_level() const { return this == &m_top_level_browsing_context; }
+    bool is_focused_context() const;
+
+    const DOM::Document* document() const { return m_document; }
+    DOM::Document* document() { return m_document; }
+
+    void set_document(DOM::Document*);
+
+    Page* page() { return m_page; }
+    const Page* page() const { return m_page; }
+
+    const Gfx::IntSize& size() const { return m_size; }
+    void set_size(const Gfx::IntSize&);
+
+    void set_needs_display(const Gfx::IntRect&);
+
+    void set_viewport_scroll_offset(const Gfx::IntPoint&);
+    Gfx::IntRect viewport_rect() const { return { m_viewport_scroll_offset, m_size }; }
+    void set_viewport_rect(const Gfx::IntRect&);
+
+    FrameLoader& loader() { return m_loader; }
+    const FrameLoader& loader() const { return m_loader; }
+
+    EventHandler& event_handler() { return m_event_handler; }
+    const EventHandler& event_handler() const { return m_event_handler; }
+
+    void scroll_to_anchor(const String&);
+
+    BrowsingContext& top_level_browsing_context() { return m_top_level_browsing_context; }
+    BrowsingContext const& top_level_browsing_context() const { return m_top_level_browsing_context; }
+
+    DOM::Element* host_element() { return m_host_element; }
+    const DOM::Element* host_element() const { return m_host_element; }
+
+    Gfx::IntPoint to_top_level_position(const Gfx::IntPoint&);
+    Gfx::IntRect to_top_level_rect(const Gfx::IntRect&);
+
+    const DOM::Position& cursor_position() const { return m_cursor_position; }
+    void set_cursor_position(DOM::Position);
+    bool increment_cursor_position_offset();
+    bool decrement_cursor_position_offset();
+
+    bool cursor_blink_state() const { return m_cursor_blink_state; }
+
+    String selected_text() const;
+
+    void did_edit(Badge<EditEventHandler>);
+
+    void register_frame_nesting(URL const&);
+    bool is_frame_nesting_allowed(URL const&) const;
+
+    void set_frame_nesting_levels(const HashMap<URL, size_t> frame_nesting_levels) { m_frame_nesting_levels = move(frame_nesting_levels); };
+    HashMap<URL, size_t> const& frame_nesting_levels() const { return m_frame_nesting_levels; }
+
+private:
+    explicit BrowsingContext(DOM::Element& host_element, BrowsingContext& top_level_browsing_context);
+    explicit BrowsingContext(Page&);
+
+    void reset_cursor_blink_cycle();
+
+    void setup();
+
+    WeakPtr<Page> m_page;
+    BrowsingContext& m_top_level_browsing_context;
+
+    FrameLoader m_loader;
+    EventHandler m_event_handler;
+
+    WeakPtr<DOM::Element> m_host_element;
+    RefPtr<DOM::Document> m_document;
+    Gfx::IntSize m_size;
+    Gfx::IntPoint m_viewport_scroll_offset;
+
+    DOM::Position m_cursor_position;
+    RefPtr<Core::Timer> m_cursor_blink_timer;
+    bool m_cursor_blink_state { false };
+
+    HashTable<ViewportClient*> m_viewport_clients;
+
+    HashMap<URL, size_t> m_frame_nesting_levels;
+};
+
+}