AK+Everywhere: Add and use weak_callback()

We have a common pattern of creating a `WeakPtr<T>` from a reference and
passing that into a lambda, to then take the strong ref when the lambda
is executed. Add `weak_callback(Weakable, lambda)` that returns a lambda
that only invokes the callback if a strong ref exists, and passes it as
the first argument.

AK/Forward.h

@@ -28,6 +28,7 @@ class Utf16StringData;
 
 enum class TrailingCodePointTransformation : u8;
 
+class AtomicRefCountedBase;
 class BigEndianInputBitStream;
 class BigEndianOutputBitStream;
 class Bitmap;
@@ -86,6 +87,9 @@ using Bytes = Span<u8>;
 template<typename T, AK::MemoryOrder DefaultMemoryOrder>
 class Atomic;
 
+template<typename T>
+class AtomicRefCounted;
+
 template<typename T, typename TSizeCalculationPolicy = DefaultSizeCalculationPolicy>
 class SinglyLinkedList;
 
@@ -176,6 +180,8 @@ class [[nodiscard]] ErrorOr;
 #if USING_AK_GLOBALLY
 using AK::Array;
 using AK::Atomic;
+using AK::AtomicRefCounted;
+using AK::AtomicRefCountedBase;
 using AK::Badge;
 using AK::BigEndianInputBitStream;
 using AK::BigEndianOutputBitStream;

AK/WeakPtr.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/Forward.h>
 #include <AK/Weakable.h>
 
 namespace AK {
@@ -173,6 +174,16 @@ private:
     RefPtr<WeakLink> m_link;
 };
 
+template<typename T, typename Callback>
+auto weak_callback(T& obj, Callback&& callback)
+requires(!IsBaseOf<AtomicRefCountedBase, T>)
+{
+    return [weak = obj.template make_weak_ptr<T>(), cb = forward<Callback>(callback)](auto&&... args) {
+        if (weak)
+            cb(*weak, forward<decltype(args)>(args)...);
+    };
+}
+
 template<typename T>
 struct Formatter<WeakPtr<T>> : Formatter<T const*> {
     ErrorOr<void> format(FormatBuilder& builder, WeakPtr<T> const& value)
@@ -193,5 +204,6 @@ struct Traits<WeakPtr<T>> : public DefaultTraits<WeakPtr<T>> {
 }
 
 #if USING_AK_GLOBALLY
+using AK::weak_callback;
 using AK::WeakPtr;
 #endif

Libraries/LibDevTools/Actors/FrameActor.cpp

@@ -45,10 +45,9 @@ FrameActor::FrameActor(DevToolsServer& devtools, String name, WeakPtr<TabActor>
 
         devtools.delegate().listen_for_console_messages(
             tab->description(),
-            [weak_self = make_weak_ptr<FrameActor>()](WebView::ConsoleOutput console_output) {
+            weak_callback(*this, [](auto& self, WebView::ConsoleOutput console_output) {
-                if (auto self = weak_self.strong_ref())
+                self.on_console_message(move(console_output));
-                    self->on_console_message(move(console_output));
+            }));
-            });
 
         // FIXME: We should adopt WebContent to inform us when style sheets are available or removed.
         devtools.delegate().retrieve_style_sheets(tab->description(),
@@ -58,33 +57,27 @@ FrameActor::FrameActor(DevToolsServer& devtools, String name, WeakPtr<TabActor>
 
         devtools.delegate().listen_for_network_events(
             tab->description(),
-            [weak_self = make_weak_ptr<FrameActor>()](DevToolsDelegate::NetworkRequestData data) {
+            weak_callback(*this, [](auto& self, DevToolsDelegate::NetworkRequestData data) {
-                if (auto self = weak_self.strong_ref())
+                self.on_network_request_started(move(data));
-                    self->on_network_request_started(move(data));
+            }),
-            },
+            weak_callback(*this, [](auto& self, DevToolsDelegate::NetworkResponseData data) {
-            [weak_self = make_weak_ptr<FrameActor>()](DevToolsDelegate::NetworkResponseData data) {
+                self.on_network_response_headers_received(move(data));
-                if (auto self = weak_self.strong_ref())
+            }),
-                    self->on_network_response_headers_received(move(data));
+            weak_callback(*this, [](auto& self, u64 request_id, ByteBuffer data) {
-            },
+                self.on_network_response_body_received(request_id, move(data));
-            [weak_self = make_weak_ptr<FrameActor>()](u64 request_id, ByteBuffer data) {
+            }),
-                if (auto self = weak_self.strong_ref())
+            weak_callback(*this, [](auto& self, DevToolsDelegate::NetworkRequestCompleteData data) {
-                    self->on_network_response_body_received(request_id, move(data));
+                self.on_network_request_finished(move(data));
-            },
+            }));
-            [weak_self = make_weak_ptr<FrameActor>()](DevToolsDelegate::NetworkRequestCompleteData data) {
-                if (auto self = weak_self.strong_ref())
-                    self->on_network_request_finished(move(data));
-            });
 
         devtools.delegate().listen_for_navigation_events(
             tab->description(),
-            [weak_self = make_weak_ptr<FrameActor>()](String url) {
+            weak_callback(*this, [](auto& self, String url) {
-                if (auto self = weak_self.strong_ref())
+                self.on_navigation_started(move(url));
-                    self->on_navigation_started(move(url));
+            }),
-            },
+            weak_callback(*this, [](auto& self, String url, String title) {
-            [weak_self = make_weak_ptr<FrameActor>()](String url, String title) {
+                self.on_navigation_finished(move(url), move(title));
-                if (auto self = weak_self.strong_ref())
+            }));
-                    self->on_navigation_finished(move(url), move(title));
-            });
     }
 }
 

Libraries/LibDevTools/Actors/PageStyleActor.cpp

@@ -122,10 +122,9 @@ PageStyleActor::PageStyleActor(DevToolsServer& devtools, String name, WeakPtr<In
 {
     if (auto tab = InspectorActor::tab_for(m_inspector)) {
         devtools.delegate().listen_for_dom_properties(tab->description(),
-            [weak_self = make_weak_ptr<PageStyleActor>()](WebView::DOMNodeProperties const& properties) {
+            weak_callback(*this, [](auto& self, WebView::DOMNodeProperties const& properties) {
-                if (auto self = weak_self.strong_ref())
+                self.received_dom_node_properties(properties);
-                    self->received_dom_node_properties(properties);
+            }));
-            });
     }
 }
 

Libraries/LibDevTools/Actors/StyleSheetsActor.cpp

@@ -25,10 +25,9 @@ StyleSheetsActor::StyleSheetsActor(DevToolsServer& devtools, String name, WeakPt
     if (auto tab = m_tab.strong_ref()) {
         devtools.delegate().listen_for_style_sheet_sources(
             tab->description(),
-            [weak_self = make_weak_ptr<StyleSheetsActor>()](Web::CSS::StyleSheetIdentifier const& style_sheet, String source) {
+            weak_callback(*this, [](auto& self, Web::CSS::StyleSheetIdentifier const& style_sheet, String source) {
-                if (auto self = weak_self.strong_ref())
+                self.style_sheet_source_received(style_sheet, move(source));
-                    self->style_sheet_source_received(style_sheet, move(source));
+            }));
-            });
     }
 }
 

Libraries/LibDevTools/Actors/WalkerActor.cpp

@@ -31,10 +31,9 @@ WalkerActor::WalkerActor(DevToolsServer& devtools, String name, WeakPtr<TabActor
 
     if (auto tab = m_tab.strong_ref()) {
         devtools.delegate().listen_for_dom_mutations(tab->description(),
-            [weak_self = make_weak_ptr<WalkerActor>()](WebView::Mutation mutation) {
+            weak_callback(*this, [](auto& self, WebView::Mutation mutation) {
-                if (auto self = weak_self.strong_ref())
+                self.new_dom_node_mutation(move(mutation));
-                    self->new_dom_node_mutation(move(mutation));
+            }));
-            });
     }
 }
 

Libraries/LibWeb/CSS/StyleValues/ImageStyleValue.cpp

@@ -69,21 +69,21 @@ void ImageStyleValue::load_any_resources(DOM::Document& document)
 
     if (m_resource_request) {
         m_resource_request->add_callbacks(
-            [this, weak_this = make_weak_ptr()] {
+            weak_callback(*this, [](auto& self) {
-                if (!weak_this || !m_document)
+                if (!self.m_document)
                     return;
 
-                for (auto* client : m_clients)
+                for (auto* client : self.m_clients)
-                    client->image_style_value_did_update(*this);
+                    client->image_style_value_did_update(self);
 
-                auto image_data = m_resource_request->image_data();
+                auto image_data = self.m_resource_request->image_data();
                 if (image_data->is_animated() && image_data->frame_count() > 1) {
-                    m_timer = Platform::Timer::create(m_document->heap());
+                    self.m_timer = Platform::Timer::create(self.m_document->heap());
-                    m_timer->set_interval(image_data->frame_duration(0));
+                    self.m_timer->set_interval(image_data->frame_duration(0));
-                    m_timer->on_timeout = GC::create_function(m_document->heap(), [this] { animate(); });
+                    self.m_timer->on_timeout = GC::create_function(self.m_document->heap(), [ptr = &self] { ptr->animate(); });
-                    m_timer->start();
+                    self.m_timer->start();
                 }
-            },
+            }),
             nullptr);
     }
 }

Services/RequestServer/ConnectionFromClient.cpp

@@ -6,6 +6,7 @@
 
 #include <AK/IDAllocator.h>
 #include <AK/NonnullOwnPtr.h>
+#include <AK/WeakPtr.h>
 #include <LibCore/EventLoop.h>
 #include <LibCore/Proxy.h>
 #include <LibCore/Socket.h>

Tests/AK/TestWeakPtr.cpp

@@ -20,10 +20,22 @@ class SimpleWeakable : public Weakable<SimpleWeakable>
 public:
     SimpleWeakable() = default;
 
+    int member() const { return m_member; }
+
 private:
     int m_member { 123 };
 };
 
+class NonRefCountedWeakable : public Weakable<NonRefCountedWeakable> {
+public:
+    NonRefCountedWeakable() = default;
+
+    int value() const { return m_value; }
+
+private:
+    int m_value { 456 };
+};
+
 #if defined(AK_COMPILER_CLANG)
 #    pragma clang diagnostic pop
 #endif
@@ -64,3 +76,72 @@ TEST_CASE(weakptr_move)
 
     EXPECT_EQ(weak2.is_null(), true);
 }
+
+TEST_CASE(weak_callback_ref_counted)
+{
+    bool was_called = false;
+
+    {
+        auto simple = adopt_ref(*new SimpleWeakable);
+        auto cb = weak_callback(*simple, [&was_called](auto& self) {
+            was_called = true;
+            EXPECT_EQ(self.member(), 123);
+        });
+
+        cb();
+        EXPECT(was_called);
+    }
+}
+
+TEST_CASE(weak_callback_ref_counted_dead)
+{
+    auto cb = [&] {
+        auto simple = adopt_ref(*new SimpleWeakable);
+        return weak_callback(*simple, [](auto&) {
+            VERIFY_NOT_REACHED();
+        });
+    }();
+
+    cb();
+}
+
+TEST_CASE(weak_callback_ref_counted_with_args)
+{
+    int received_value = 0;
+
+    auto simple = adopt_ref(*new SimpleWeakable);
+    auto cb = weak_callback(*simple, [&received_value](auto& self, int value) {
+        received_value = value + self.member();
+    });
+
+    cb(42);
+    EXPECT_EQ(received_value, 42 + 123);
+}
+
+TEST_CASE(weak_callback_non_ref_counted)
+{
+    bool was_called = false;
+
+    {
+        NonRefCountedWeakable obj;
+        auto cb = weak_callback(obj, [&was_called](auto& self) {
+            was_called = true;
+            EXPECT_EQ(self.value(), 456);
+        });
+
+        cb();
+        EXPECT(was_called);
+    }
+}
+
+TEST_CASE(weak_callback_non_ref_counted_dead)
+{
+    auto cb = [&] {
+        NonRefCountedWeakable obj;
+        return weak_callback(obj, [](auto&) {
+            VERIFY_NOT_REACHED();
+        });
+    }();
+
+    cb();
+}