LibWeb: Make Frame point weakly to Page

This patch makes Page weakable and allows page-less frames to exist.

Page is single-owner, and Frame is multiple-owner, so it's not sound
for Frame to assume its containing Page will stick around for its own
entire lifetime.

Fixes #3976.

12 files changed, 87 insertions, 56 deletions

diff --git a/Libraries/LibWeb/CSS/StyleValue.cpp b/Libraries/LibWeb/CSS/StyleValue.cpp
index c744e29053..79054484b3 100644
--- a/Libraries/LibWeb/CSS/StyleValue.cpp
+++ b/Libraries/LibWeb/CSS/StyleValue.cpp
@@ -172,7 +172,8 @@ Color IdentifierStyleValue::to_color(const DOM::Document& document) const
     if (id() == CSS::ValueID::VendorSpecificLink)
         return document.link_color();
 
-    auto palette = document.frame()->page().palette();
+    ASSERT(document.page());
+    auto palette = document.page()->palette();
     switch (id()) {
     case CSS::ValueID::VendorSpecificPaletteDesktopBackground:
         return palette.color(ColorRole::DesktopBackground);
diff --git a/Libraries/LibWeb/DOM/Document.cpp b/Libraries/LibWeb/DOM/Document.cpp
index 4f2084fe0e..43f3486362 100644
--- a/Libraries/LibWeb/DOM/Document.cpp
+++ b/Libraries/LibWeb/DOM/Document.cpp
@@ -343,8 +343,10 @@ void Document::layout()
     m_layout_root->layout();
     m_layout_root->set_needs_display();
 
-    if (frame()->is_main_frame())
-        frame()->page().client().page_did_layout();
+    if (frame()->is_main_frame()) {
+        if (auto* page = this->page())
+            page->client().page_did_layout();
+    }
 }
 
 void Document::update_style()
@@ -446,27 +448,27 @@ Color Document::link_color() const
 {
     if (m_link_color.has_value())
         return m_link_color.value();
-    if (!frame())
+    if (!page())
         return Color::Blue;
-    return frame()->page().palette().link();
+    return page()->palette().link();
 }
 
 Color Document::active_link_color() const
 {
     if (m_active_link_color.has_value())
         return m_active_link_color.value();
-    if (!frame())
+    if (!page())
         return Color::Red;
-    return frame()->page().palette().active_link();
+    return page()->palette().active_link();
 }
 
 Color Document::visited_link_color() const
 {
     if (m_visited_link_color.has_value())
         return m_visited_link_color.value();
-    if (!frame())
+    if (!page())
         return Color::Magenta;
-    return frame()->page().palette().visited_link();
+    return page()->palette().visited_link();
 }
 
 static JS::VM& main_thread_vm()
@@ -596,4 +598,14 @@ void Document::set_ready_state(const String& ready_state)
     dispatch_event(Event::create("readystatechange"));
 }
 
+Page* Document::page()
+{
+    return m_frame ? m_frame->page() : nullptr;
+}
+
+const Page* Document::page() const
+{
+    return m_frame ? m_frame->page() : nullptr;
+}
+
 }
diff --git a/Libraries/LibWeb/DOM/Document.h b/Libraries/LibWeb/DOM/Document.h
index b179254867..f6699bb2c6 100644
--- a/Libraries/LibWeb/DOM/Document.h
+++ b/Libraries/LibWeb/DOM/Document.h
@@ -99,6 +99,9 @@ public:
     Frame* frame() { return m_frame.ptr(); }
     const Frame* frame() const { return m_frame.ptr(); }
 
+    Page* page();
+    const Page* page() const;
+
     Color background_color(const Gfx::Palette&) const;
     RefPtr<Gfx::Bitmap> background_image() const;
 
diff --git a/Libraries/LibWeb/DOM/Window.cpp b/Libraries/LibWeb/DOM/Window.cpp
index cb76b91bea..cdf88d6b3d 100644
--- a/Libraries/LibWeb/DOM/Window.cpp
+++ b/Libraries/LibWeb/DOM/Window.cpp
@@ -61,9 +61,8 @@ void Window::set_wrapper(Badge<Bindings::WindowObject>, Bindings::WindowObject&
 
 void Window::alert(const String& message)
 {
-    if (!m_document.frame())
-        return;
-    m_document.frame()->page().client().page_did_request_alert(message);
+    if (auto* page = m_document.page())
+        page->client().page_did_request_alert(message);
 }
 
 bool Window::confirm(const String& message)
diff --git a/Libraries/LibWeb/HTML/HTMLFormElement.cpp b/Libraries/LibWeb/HTML/HTMLFormElement.cpp
index ebafd9a465..b709538cff 100644
--- a/Libraries/LibWeb/HTML/HTMLFormElement.cpp
+++ b/Libraries/LibWeb/HTML/HTMLFormElement.cpp
@@ -105,7 +105,8 @@ void HTMLFormElement::submit(RefPtr<HTMLInputElement> submitter)
         request.set_body(body);
     }
 
-    document().frame()->page().load(request);
+    if (auto* page = document().page())
+        page->load(request);
 }
 
 }
diff --git a/Libraries/LibWeb/HTML/HTMLInputElement.cpp b/Libraries/LibWeb/HTML/HTMLInputElement.cpp
index bf721ed071..3ab1443e6e 100644
--- a/Libraries/LibWeb/HTML/HTMLInputElement.cpp
+++ b/Libraries/LibWeb/HTML/HTMLInputElement.cpp
@@ -62,9 +62,9 @@ void HTMLInputElement::did_click_button(Badge<LayoutButton>)
 
 RefPtr<LayoutNode> HTMLInputElement::create_layout_node(const CSS::StyleProperties* parent_style)
 {
-    ASSERT(document().frame());
-    auto& frame = *document().frame();
-    auto& page_view = const_cast<InProcessWebView&>(static_cast<const InProcessWebView&>(frame.page().client()));
+    ASSERT(document().page());
+    auto& page = *document().page();
+    auto& page_view = const_cast<InProcessWebView&>(static_cast<const InProcessWebView&>(page.client()));
 
     if (type() == "hidden")
         return nullptr;
diff --git a/Libraries/LibWeb/Layout/LayoutWidget.cpp b/Libraries/LibWeb/Layout/LayoutWidget.cpp
index fe79e0aa67..a80394a8a9 100644
--- a/Libraries/LibWeb/Layout/LayoutWidget.cpp
+++ b/Libraries/LibWeb/Layout/LayoutWidget.cpp
@@ -60,7 +60,7 @@ void LayoutWidget::did_set_rect()
 void LayoutWidget::update_widget()
 {
     auto adjusted_widget_position = absolute_rect().location().to_type<int>();
-    auto& page_view = static_cast<const InProcessWebView&>(frame().page().client());
+    auto& page_view = static_cast<const InProcessWebView&>(frame().page()->client());
     adjusted_widget_position.move_by(-page_view.horizontal_scrollbar().value(), -page_view.vertical_scrollbar().value());
     widget().move_to(adjusted_widget_position);
 }
diff --git a/Libraries/LibWeb/Loader/FrameLoader.cpp b/Libraries/LibWeb/Loader/FrameLoader.cpp
index 087ab4fbc2..8e11a24331 100644
--- a/Libraries/LibWeb/Loader/FrameLoader.cpp
+++ b/Libraries/LibWeb/Loader/FrameLoader.cpp
@@ -160,8 +160,10 @@ bool FrameLoader::load(const LoadRequest& request, Type type)
 
     set_resource(ResourceLoader::the().load_resource(Resource::Type::Generic, request));
 
-    if (type == Type::Navigation)
-        frame().page().client().page_did_start_loading(url);
+    if (type == Type::Navigation) {
+        if (auto* page = frame().page())
+            page->client().page_did_start_loading(url);
+    }
 
     if (type == Type::IFrame)
         return true;
@@ -184,7 +186,8 @@ bool FrameLoader::load(const LoadRequest& request, Type type)
                     return;
                 }
                 dbg() << "Decoded favicon, " << bitmap->size();
-                frame().page().client().page_did_change_favicon(*bitmap);
+                if (auto* page = frame().page())
+                    page->client().page_did_change_favicon(*bitmap);
             });
     }
 
diff --git a/Libraries/LibWeb/Page/EventHandler.cpp b/Libraries/LibWeb/Page/EventHandler.cpp
index c75d41c0bb..ad10e0b77d 100644
--- a/Libraries/LibWeb/Page/EventHandler.cpp
+++ b/Libraries/LibWeb/Page/EventHandler.cpp
@@ -125,7 +125,6 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
     }
 
     NonnullRefPtr document = *m_frame.document();
-    auto& page_client = m_frame.page().client();
 
     auto result = layout_root()->hit_test(position, HitTestType::Exact);
     if (!result.layout_node)
@@ -148,7 +147,8 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
         return false;
     }
 
-    m_frame.page().set_focused_frame({}, m_frame);
+    if (auto* page = m_frame.page())
+        page->set_focused_frame({}, m_frame);
 
     auto offset = compute_mouse_event_offset(position, *result.layout_node);
     node->dispatch_event(UIEvents::MouseEvent::create("mousedown", offset.x(), offset.y()));
@@ -158,7 +158,8 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
     if (button == GUI::MouseButton::Right && is<HTML::HTMLImageElement>(*node)) {
         auto& image_element = downcast<HTML::HTMLImageElement>(*node);
         auto image_url = image_element.document().complete_url(image_element.src());
-        page_client.page_did_request_image_context_menu(m_frame.to_main_frame_position(position), image_url, "", modifiers, image_element.bitmap());
+        if (auto* page = m_frame.page())
+            page->client().page_did_request_image_context_menu(m_frame.to_main_frame_position(position), image_url, "", modifiers, image_element.bitmap());
         return true;
     }
 
@@ -176,16 +177,19 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
                 m_frame.scroll_to_anchor(anchor);
             } else {
                 if (m_frame.is_main_frame()) {
-                    page_client.page_did_click_link(url, link->target(), modifiers);
+                    if (auto* page = m_frame.page())
+                        page->client().page_did_click_link(url, link->target(), modifiers);
                 } else {
                     // FIXME: Handle different targets!
                     m_frame.loader().load(url, FrameLoader::Type::Navigation);
                 }
             }
         } else if (button == GUI::MouseButton::Right) {
-            page_client.page_did_request_link_context_menu(m_frame.to_main_frame_position(position), url, link->target(), modifiers);
+            if (auto* page = m_frame.page())
+                page->client().page_did_request_link_context_menu(m_frame.to_main_frame_position(position), url, link->target(), modifiers);
         } else if (button == GUI::MouseButton::Middle) {
-            page_client.page_did_middle_click_link(url, link->target(), modifiers);
+            if (auto* page = m_frame.page())
+                page->client().page_did_middle_click_link(url, link->target(), modifiers);
         }
     } else {
         if (button == GUI::MouseButton::Left) {
@@ -197,7 +201,8 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
                 m_in_mouse_selection = true;
             }
         } else if (button == GUI::MouseButton::Right) {
-            page_client.page_did_request_context_menu(m_frame.to_main_frame_position(position));
+            if (auto* page = m_frame.page())
+                page->client().page_did_request_context_menu(m_frame.to_main_frame_position(position));
         }
     }
     return true;
@@ -214,7 +219,6 @@ bool EventHandler::handle_mousemove(const Gfx::IntPoint& position, unsigned butt
     }
 
     auto& document = *m_frame.document();
-    auto& page_client = m_frame.page().client();
 
     bool hovered_node_changed = false;
     bool is_hovering_link = false;
@@ -227,7 +231,8 @@ bool EventHandler::handle_mousemove(const Gfx::IntPoint& position, unsigned butt
             document.set_hovered_node(result.layout_node->node());
             result.layout_node->handle_mousemove({}, position, buttons, modifiers);
             // FIXME: It feels a bit aggressive to always update the cursor like this.
-            page_client.page_did_request_cursor_change(Gfx::StandardCursor::None);
+            if (auto* page = m_frame.page())
+                page->client().page_did_request_cursor_change(Gfx::StandardCursor::None);
             return true;
         }
 
@@ -262,28 +267,31 @@ bool EventHandler::handle_mousemove(const Gfx::IntPoint& position, unsigned butt
                 layout_root()->set_selection_end({ hit.layout_node, hit.index_in_node });
             }
             dump_selection("MouseMove");
-            page_client.page_did_change_selection();
+            if (auto* page = m_frame.page())
+                page->client().page_did_change_selection();
         }
     }
 
-    if (is_hovering_link)
-        page_client.page_did_request_cursor_change(Gfx::StandardCursor::Hand);
-    else if (is_hovering_text)
-        page_client.page_did_request_cursor_change(Gfx::StandardCursor::IBeam);
-    else
-        page_client.page_did_request_cursor_change(Gfx::StandardCursor::None);
-
-    if (hovered_node_changed) {
-        RefPtr<HTML::HTMLElement> hovered_html_element = document.hovered_node() ? document.hovered_node()->enclosing_html_element() : nullptr;
-        if (hovered_html_element && !hovered_html_element->title().is_null()) {
-            page_client.page_did_enter_tooltip_area(m_frame.to_main_frame_position(position), hovered_html_element->title());
-        } else {
-            page_client.page_did_leave_tooltip_area();
-        }
+    if (auto* page = m_frame.page()) {
         if (is_hovering_link)
-            page_client.page_did_hover_link(document.complete_url(hovered_link_element->href()));
+            page->client().page_did_request_cursor_change(Gfx::StandardCursor::Hand);
+        else if (is_hovering_text)
+            page->client().page_did_request_cursor_change(Gfx::StandardCursor::IBeam);
         else
-            page_client.page_did_unhover_link();
+            page->client().page_did_request_cursor_change(Gfx::StandardCursor::None);
+
+        if (hovered_node_changed) {
+            RefPtr<HTML::HTMLElement> hovered_html_element = document.hovered_node() ? document.hovered_node()->enclosing_html_element() : nullptr;
+            if (hovered_html_element && !hovered_html_element->title().is_null()) {
+                page->client().page_did_enter_tooltip_area(m_frame.to_main_frame_position(position), hovered_html_element->title());
+            } else {
+                page->client().page_did_leave_tooltip_area();
+            }
+            if (is_hovering_link)
+                page->client().page_did_hover_link(document.complete_url(hovered_link_element->href()));
+            else
+                page->client().page_did_unhover_link();
+        }
     }
     return true;
 }
diff --git a/Libraries/LibWeb/Page/Frame.cpp b/Libraries/LibWeb/Page/Frame.cpp
index ff501d0d73..f7b5a7ed78 100644
--- a/Libraries/LibWeb/Page/Frame.cpp
+++ b/Libraries/LibWeb/Page/Frame.cpp
@@ -36,7 +36,7 @@
 namespace Web {
 
 Frame::Frame(DOM::Element& host_element, Frame& main_frame)
-    : m_page(main_frame.page())
+    : m_page(*main_frame.page())
     , m_main_frame(main_frame)
     , m_loader(*this)
     , m_event_handler({}, *this)
@@ -72,7 +72,7 @@ void Frame::setup()
 
 bool Frame::is_focused_frame() const
 {
-    return this == &page().focused_frame();
+    return m_page && &m_page->focused_frame() == this;
 }
 
 void Frame::set_document(DOM::Document* document)
@@ -89,10 +89,12 @@ void Frame::set_document(DOM::Document* document)
 
     if (m_document) {
         m_document->attach_to_frame({}, *this);
-        page().client().page_did_change_title(m_document->title());
+        if (m_page)
+            m_page->client().page_did_change_title(m_document->title());
     }
 
-    page().client().page_did_set_document_in_main_frame(m_document);
+    if (m_page)
+        m_page->client().page_did_set_document_in_main_frame(m_document);
 }
 
 void Frame::set_size(const Gfx::IntSize& size)
@@ -120,7 +122,8 @@ void Frame::set_needs_display(const Gfx::IntRect& rect)
         return;
 
     if (is_main_frame()) {
-        page().client().page_did_invalidate(to_main_frame_rect(rect));
+        if (m_page)
+            m_page->client().page_did_invalidate(to_main_frame_rect(rect));
         return;
     }
 
@@ -168,7 +171,8 @@ void Frame::scroll_to_anchor(const String& fragment)
         float_rect.move_by(-padding_box.left, -padding_box.top);
     }
 
-    page().client().page_did_request_scroll_into_view(enclosing_int_rect(float_rect));
+    if (m_page)
+        m_page->client().page_did_request_scroll_into_view(enclosing_int_rect(float_rect));
 }
 
 Gfx::IntRect Frame::to_main_frame_rect(const Gfx::IntRect& a_rect)
diff --git a/Libraries/LibWeb/Page/Frame.h b/Libraries/LibWeb/Page/Frame.h
index bb0145d540..2696454182 100644
--- a/Libraries/LibWeb/Page/Frame.h
+++ b/Libraries/LibWeb/Page/Frame.h
@@ -55,8 +55,8 @@ public:
 
     void set_document(DOM::Document*);
 
-    Page& page() { return m_page; }
-    const Page& page() const { return m_page; }
+    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&);
@@ -100,7 +100,7 @@ private:
 
     void setup();
 
-    Page& m_page;
+    WeakPtr<Page> m_page;
     Frame& m_main_frame;
 
     FrameLoader m_loader;
diff --git a/Libraries/LibWeb/Page/Page.h b/Libraries/LibWeb/Page/Page.h
index 0b9094d7f2..8fa1719d2e 100644
--- a/Libraries/LibWeb/Page/Page.h
+++ b/Libraries/LibWeb/Page/Page.h
@@ -40,7 +40,7 @@ namespace Web {
 
 class PageClient;
 
-class Page {
+class Page : public Weakable<Page> {
     AK_MAKE_NONCOPYABLE(Page);
     AK_MAKE_NONMOVABLE(Page);