diff --git a/browser/components/shell/nsGNOMEShellService.cpp b/browser/components/shell/nsGNOMEShellService.cpp
index 4db6a3a601c8..f9849833b15d 100644
--- a/browser/components/shell/nsGNOMEShellService.cpp
+++ b/browser/components/shell/nsGNOMEShellService.cpp
@@ -22,6 +22,7 @@
 #include "nsIImageLoadingContent.h"
 #include "imgIRequest.h"
 #include "imgIContainer.h"
+#include "mozilla/GRefPtr.h"
 #include "mozilla/Sprintf.h"
 #include "mozilla/WidgetUtils.h"
 #include "mozilla/WidgetUtilsGtk.h"
@@ -357,14 +358,12 @@ nsGNOMEShellService::GetCanSetDesktopBackground(bool* aResult) {
 }
 
 static nsresult WriteImage(const nsCString& aPath, imgIContainer* aImage) {
-  GdkPixbuf* pixbuf = nsImageToPixbuf::ImageToPixbuf(aImage);
+  RefPtr<GdkPixbuf> pixbuf = nsImageToPixbuf::ImageToPixbuf(aImage);
   if (!pixbuf) {
     return NS_ERROR_NOT_AVAILABLE;
   }
 
   gboolean res = gdk_pixbuf_save(pixbuf, aPath.get(), "png", nullptr, nullptr);
-
-  g_object_unref(pixbuf);
   return res ? NS_OK : NS_ERROR_FAILURE;
 }
 
diff --git a/hal/linux/UPowerClient.cpp b/hal/linux/UPowerClient.cpp
index 8bf732e233f9..1de38ad201ea 100644
--- a/hal/linux/UPowerClient.cpp
+++ b/hal/linux/UPowerClient.cpp
@@ -9,26 +9,13 @@
 #include <dbus/dbus-glib-lowlevel.h>
 #include <mozilla/Attributes.h>
 #include <mozilla/dom/battery/Constants.h>
-#include "nsAutoRef.h"
+#include "mozilla/GRefPtr.h"
+#include "mozilla/GUniquePtr.h"
 #include <cmath>
 
-/*
- * Helper that manages the destruction of glib objects as soon as they leave
- * the current scope.
- *
- * We are specializing nsAutoRef class.
- */
-
-template <>
-class nsAutoRefTraits<GHashTable> : public nsPointerRefTraits<GHashTable> {
- public:
-  static void Release(GHashTable* ptr) { g_hash_table_unref(ptr); }
-};
-
 using namespace mozilla::dom::battery;
 
-namespace mozilla {
-namespace hal_impl {
+namespace mozilla::hal_impl {
 
 /**
  * This is the declaration of UPowerClient class. This class is listening and
@@ -69,9 +56,8 @@ class UPowerClient {
 
   /**
    * Returns a hash table with the properties of aDevice.
-   * Note: the caller has to unref the hash table.
    */
-  GHashTable* GetDevicePropertiesSync(DBusGProxy* aProxy);
+  already_AddRefed<GHashTable> GetDevicePropertiesSync(DBusGProxy* aProxy);
   void GetDevicePropertiesAsync(DBusGProxy* aProxy);
   static void GetDevicePropertiesCallback(DBusGProxy* aProxy,
                                           DBusGProxyCall* aCall, void* aData);
@@ -104,16 +90,16 @@ class UPowerClient {
                                                   void* aData);
 
   // The DBus connection object.
-  DBusGConnection* mDBusConnection;
+  RefPtr<DBusGConnection> mDBusConnection;
 
   // The DBus proxy object to upower.
-  DBusGProxy* mUPowerProxy;
+  RefPtr<DBusGProxy> mUPowerProxy;
 
   // The path of the tracked device.
-  gchar* mTrackedDevice;
+  GUniquePtr<gchar> mTrackedDevice;
 
   // The DBusGProxy for the tracked device.
-  DBusGProxy* mTrackedDeviceProxy;
+  RefPtr<DBusGProxy> mTrackedDeviceProxy;
 
   double mLevel;
   bool mCharging;
@@ -163,11 +149,7 @@ UPowerClient* UPowerClient::GetInstance() {
 }
 
 UPowerClient::UPowerClient()
-    : mDBusConnection(nullptr),
-      mUPowerProxy(nullptr),
-      mTrackedDevice(nullptr),
-      mTrackedDeviceProxy(nullptr),
-      mLevel(kDefaultLevel),
+    : mLevel(kDefaultLevel),
       mCharging(kDefaultCharging),
       mRemainingTime(kDefaultRemainingTime) {}
 
@@ -179,12 +161,12 @@ UPowerClient::~UPowerClient() {
 }
 
 void UPowerClient::BeginListening() {
-  GError* error = nullptr;
-  mDBusConnection = dbus_g_bus_get(DBUS_BUS_SYSTEM, &error);
+  GUniquePtr<GError> error;
+  mDBusConnection =
+      dont_AddRef(dbus_g_bus_get(DBUS_BUS_SYSTEM, getter_Transfers(error)));
 
   if (!mDBusConnection) {
     HAL_LOG("Failed to open connection to bus: %s\n", error->message);
-    g_error_free(error);
     return;
   }
 
@@ -199,9 +181,9 @@ void UPowerClient::BeginListening() {
   dbus_connection_add_filter(dbusConnection, ConnectionSignalFilter, this,
                              nullptr);
 
-  mUPowerProxy = dbus_g_proxy_new_for_name(
+  mUPowerProxy = dont_AddRef(dbus_g_proxy_new_for_name(
       mDBusConnection, "org.freedesktop.UPower", "/org/freedesktop/UPower",
-      "org.freedesktop.UPower");
+      "org.freedesktop.UPower"));
 
   UpdateTrackedDeviceSync();
 
@@ -231,21 +213,15 @@ void UPowerClient::StopListening() {
   dbus_g_proxy_disconnect_signal(mUPowerProxy, "DeviceChanged",
                                  G_CALLBACK(DeviceChanged), this);
 
-  g_free(mTrackedDevice);
   mTrackedDevice = nullptr;
 
   if (mTrackedDeviceProxy) {
     dbus_g_proxy_disconnect_signal(mTrackedDeviceProxy, "PropertiesChanged",
                                    G_CALLBACK(PropertiesChanged), this);
-
-    g_object_unref(mTrackedDeviceProxy);
     mTrackedDeviceProxy = nullptr;
   }
 
-  g_object_unref(mUPowerProxy);
   mUPowerProxy = nullptr;
-
-  dbus_g_connection_unref(mDBusConnection);
   mDBusConnection = nullptr;
 
   // We should now show the default values, not the latest we got.
@@ -258,27 +234,23 @@ void UPowerClient::UpdateTrackedDeviceSync() {
   GType typeGPtrArray =
       dbus_g_type_get_collection("GPtrArray", DBUS_TYPE_G_OBJECT_PATH);
   GPtrArray* devices = nullptr;
-  GError* error = nullptr;
 
   // Reset the current tracked device:
-  g_free(mTrackedDevice);
   mTrackedDevice = nullptr;
 
   // Reset the current tracked device proxy:
   if (mTrackedDeviceProxy) {
     dbus_g_proxy_disconnect_signal(mTrackedDeviceProxy, "PropertiesChanged",
                                    G_CALLBACK(PropertiesChanged), this);
-
-    g_object_unref(mTrackedDeviceProxy);
     mTrackedDeviceProxy = nullptr;
   }
 
+  GUniquePtr<GError> error;
   // If that fails, that likely means upower isn't installed.
-  if (!dbus_g_proxy_call(mUPowerProxy, "EnumerateDevices", &error,
-                         G_TYPE_INVALID, typeGPtrArray, &devices,
-                         G_TYPE_INVALID)) {
+  if (!dbus_g_proxy_call(mUPowerProxy, "EnumerateDevices",
+                         getter_Transfers(error), G_TYPE_INVALID, typeGPtrArray,
+                         &devices, G_TYPE_INVALID)) {
     HAL_LOG("Error: %s\n", error->message);
-    g_error_free(error);
     return;
   }
 
@@ -287,23 +259,25 @@ void UPowerClient::UpdateTrackedDeviceSync() {
    * TODO: we could try to combine more than one battery.
    */
   for (guint i = 0; i < devices->len; ++i) {
-    gchar* devicePath = static_cast<gchar*>(g_ptr_array_index(devices, i));
+    GUniquePtr<gchar> devicePath(
+        static_cast<gchar*>(g_ptr_array_index(devices, i)));
+    if (mTrackedDevice) {
+      continue;
+    }
 
-    DBusGProxy* proxy = dbus_g_proxy_new_from_proxy(
-        mUPowerProxy, "org.freedesktop.DBus.Properties", devicePath);
+    RefPtr<DBusGProxy> proxy = dont_AddRef(dbus_g_proxy_new_from_proxy(
+        mUPowerProxy, "org.freedesktop.DBus.Properties", devicePath.get()));
 
-    nsAutoRef<GHashTable> hashTable(GetDevicePropertiesSync(proxy));
+    RefPtr<GHashTable> hashTable(GetDevicePropertiesSync(proxy));
 
     if (g_value_get_uint(static_cast<const GValue*>(
             g_hash_table_lookup(hashTable, "Type"))) == sDeviceTypeBattery) {
       UpdateSavedInfo(hashTable);
-      mTrackedDevice = devicePath;
-      mTrackedDeviceProxy = proxy;
-      break;
+      mTrackedDevice = std::move(devicePath);
+      mTrackedDeviceProxy = std::move(proxy);
+      // Can't break here because we still need to iterate over all other
+      // devices to free them.
     }
-
-    g_object_unref(proxy);
-    g_free(devicePath);
   }
 
   if (mTrackedDeviceProxy) {
@@ -326,9 +300,9 @@ void UPowerClient::DeviceChanged(DBusGProxy* aProxy, const gchar* aObjectPath,
   }
 
 #if GLIB_MAJOR_VERSION >= 2 && GLIB_MINOR_VERSION >= 16
-  if (g_strcmp0(aObjectPath, aListener->mTrackedDevice)) {
+  if (g_strcmp0(aObjectPath, aListener->mTrackedDevice.get())) {
 #else
-  if (g_ascii_strcasecmp(aObjectPath, aListener->mTrackedDevice)) {
+  if (g_ascii_strcasecmp(aObjectPath, aListener->mTrackedDevice.get())) {
 #endif
     return;
   }
@@ -355,34 +329,35 @@ DBusHandlerResult UPowerClient::ConnectionSignalFilter(
   return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 }
 
-GHashTable* UPowerClient::GetDevicePropertiesSync(DBusGProxy* aProxy) {
-  GError* error = nullptr;
-  GHashTable* hashTable = nullptr;
+already_AddRefed<GHashTable> UPowerClient::GetDevicePropertiesSync(
+    DBusGProxy* aProxy) {
+  GUniquePtr<GError> error;
+  RefPtr<GHashTable> hashTable;
   GType typeGHashTable =
       dbus_g_type_get_map("GHashTable", G_TYPE_STRING, G_TYPE_VALUE);
-  if (!dbus_g_proxy_call(aProxy, "GetAll", &error, G_TYPE_STRING,
-                         "org.freedesktop.UPower.Device", G_TYPE_INVALID,
-                         typeGHashTable, &hashTable, G_TYPE_INVALID)) {
+  if (!dbus_g_proxy_call(aProxy, "GetAll", getter_Transfers(error),
+                         G_TYPE_STRING, "org.freedesktop.UPower.Device",
+                         G_TYPE_INVALID, typeGHashTable,
+                         hashTable.StartAssignment(), G_TYPE_INVALID)) {
     HAL_LOG("Error: %s\n", error->message);
-    g_error_free(error);
     return nullptr;
   }
 
-  return hashTable;
+  return hashTable.forget();
 }
 
 /* static */
 void UPowerClient::GetDevicePropertiesCallback(DBusGProxy* aProxy,
                                                DBusGProxyCall* aCall,
                                                void* aData) {
-  GError* error = nullptr;
-  GHashTable* hashTable = nullptr;
+  GUniquePtr<GError> error;
+  RefPtr<GHashTable> hashTable;
   GType typeGHashTable =
       dbus_g_type_get_map("GHashTable", G_TYPE_STRING, G_TYPE_VALUE);
-  if (!dbus_g_proxy_end_call(aProxy, aCall, &error, typeGHashTable, &hashTable,
+  if (!dbus_g_proxy_end_call(aProxy, aCall, getter_Transfers(error),
+                             typeGHashTable, hashTable.StartAssignment(),
                              G_TYPE_INVALID)) {
     HAL_LOG("Error: %s\n", error->message);
-    g_error_free(error);
   } else {
     sInstance->UpdateSavedInfo(hashTable);
     hal::NotifyBatteryChange(hal::BatteryInformation(
@@ -470,5 +445,4 @@ bool UPowerClient::IsCharging() { return mCharging; }
 
 double UPowerClient::GetRemainingTime() { return mRemainingTime; }
 
-}  // namespace hal_impl
-}  // namespace mozilla
+}  // namespace mozilla::hal_impl
diff --git a/hal/moz.build b/hal/moz.build
index eb6935eea7cd..71501fddac16 100644
--- a/hal/moz.build
+++ b/hal/moz.build
@@ -45,6 +45,7 @@ if CONFIG["MOZ_WIDGET_TOOLKIT"] == "android":
         "android/AndroidHal.cpp",
     ]
 elif CONFIG["OS_TARGET"] == "Linux":
+
     UNIFIED_SOURCES += [
         "fallback/FallbackProcessPriority.cpp",
         "fallback/FallbackScreenConfiguration.cpp",
@@ -127,6 +128,8 @@ LOCAL_INCLUDES += [
 ]
 
 CFLAGS += CONFIG["GLIB_CFLAGS"]
+CFLAGS += CONFIG["MOZ_GTK3_CFLAGS"]
 CFLAGS += CONFIG["MOZ_DBUS_GLIB_CFLAGS"]
 CXXFLAGS += CONFIG["GLIB_CFLAGS"]
+CXXFLAGS += CONFIG["MOZ_GTK3_CFLAGS"]
 CXXFLAGS += CONFIG["MOZ_DBUS_GLIB_CFLAGS"]
diff --git a/toolkit/system/gnome/nsAlertsIconListener.cpp b/toolkit/system/gnome/nsAlertsIconListener.cpp
index c64f2eb067b2..e4b859438786 100644
--- a/toolkit/system/gnome/nsAlertsIconListener.cpp
+++ b/toolkit/system/gnome/nsAlertsIconListener.cpp
@@ -16,11 +16,15 @@
 #include "nsIObserverService.h"
 #include "nsCRT.h"
 #include "mozilla/XREAppData.h"
+#include "mozilla/GRefPtr.h"
+#include "mozilla/GUniquePtr.h"
+#include "mozilla/UniquePtrExtensions.h"
 
 #include <dlfcn.h>
 #include <gdk/gdk.h>
 
-extern const mozilla::StaticXREAppData* gAppData;
+using namespace mozilla;
+extern const StaticXREAppData* gAppData;
 
 static bool gHasActions = false;
 static bool gHasCaps = false;
@@ -64,7 +68,8 @@ static void notify_closed_marshal(GClosure* closure, GValue* return_value,
   NS_RELEASE(alert);
 }
 
-static GdkPixbuf* GetPixbufFromImgRequest(imgIRequest* aRequest) {
+static already_AddRefed<GdkPixbuf> GetPixbufFromImgRequest(
+    imgIRequest* aRequest) {
   nsCOMPtr<imgIContainer> image;
   nsresult rv = aRequest->GetImage(getter_AddRefs(image));
   if (NS_FAILED(rv)) {
@@ -145,14 +150,8 @@ nsAlertsIconListener::OnImageMissing(nsISupports*) {
 
 NS_IMETHODIMP
 nsAlertsIconListener::OnImageReady(nsISupports*, imgIRequest* aRequest) {
-  GdkPixbuf* imagePixbuf = GetPixbufFromImgRequest(aRequest);
-  if (!imagePixbuf) {
-    ShowAlert(nullptr);
-  } else {
-    ShowAlert(imagePixbuf);
-    g_object_unref(imagePixbuf);
-  }
-
+  RefPtr<GdkPixbuf> imagePixbuf = GetPixbufFromImgRequest(aRequest);
+  ShowAlert(imagePixbuf);
   return NS_OK;
 }
 
@@ -202,10 +201,9 @@ nsresult nsAlertsIconListener::ShowAlert(GdkPixbuf* aPixbuf) {
   g_closure_set_marshal(closure, notify_closed_marshal);
   mClosureHandler =
       g_signal_connect_closure(mNotification, "closed", closure, FALSE);
-  GError* error = nullptr;
-  if (!notify_notification_show(mNotification, &error)) {
+  GUniquePtr<GError> error;
+  if (!notify_notification_show(mNotification, getter_Transfers(error))) {
     NS_WARNING(error->message);
-    g_error_free(error);
     return NS_ERROR_FAILURE;
   }
 
@@ -253,10 +251,9 @@ nsresult nsAlertsIconListener::Close() {
     return NS_OK;
   }
 
-  GError* error = nullptr;
-  if (!notify_notification_close(mNotification, &error)) {
+  GUniquePtr<GError> error;
+  if (!notify_notification_close(mNotification, getter_Transfers(error))) {
     NS_WARNING(error->message);
-    g_error_free(error);
     return NS_ERROR_FAILURE;
   }
 
diff --git a/toolkit/system/gnome/nsGIOService.cpp b/toolkit/system/gnome/nsGIOService.cpp
index 447884c0fef3..1358ea163310 100644
--- a/toolkit/system/gnome/nsGIOService.cpp
+++ b/toolkit/system/gnome/nsGIOService.cpp
@@ -73,7 +73,7 @@ nsFlatpakHandlerApp::LaunchWithURI(
     nsIURI* aUri, mozilla::dom::BrowsingContext* aBrowsingContext) {
   nsCString spec;
   aUri->GetSpec(spec);
-  GError* error = nullptr;
+  GUniquePtr<GError> error;
 
   // The TMPDIR where files are downloaded when user choose to open them
   // needs to be accessible from sandbox and host. The default settings
@@ -81,12 +81,11 @@ nsFlatpakHandlerApp::LaunchWithURI(
   // why the gtk_show_uri fails there.
   // The workaround is to set TMPDIR environment variable in sandbox to
   // $XDG_CACHE_HOME/tmp before executing Firefox.
-  gtk_show_uri(nullptr, spec.get(), GDK_CURRENT_TIME, &error);
+  gtk_show_uri(nullptr, spec.get(), GDK_CURRENT_TIME, getter_Transfers(error));
   if (error) {
     NS_WARNING(
         nsPrintfCString("Cannot launch flatpak handler: %s", error->message)
             .get());
-    g_error_free(error);
     return NS_ERROR_FAILURE;
   }
   return NS_OK;
@@ -100,13 +99,12 @@ nsFlatpakHandlerApp::LaunchWithURI(
  */
 static nsresult GetCommandFromCommandline(
     nsACString const& aCommandWithArguments, nsACString& aCommand) {
-  GError* error = nullptr;
+  GUniquePtr<GError> error;
   gchar** argv = nullptr;
   if (!g_shell_parse_argv(aCommandWithArguments.BeginReading(), nullptr, &argv,
-                          &error) ||
+                          getter_Transfers(error)) ||
       !argv[0]) {
     g_warning("Cannot parse command with arguments: %s", error->message);
-    g_error_free(error);
     g_strfreev(argv);
     return NS_ERROR_FAILURE;
   }
@@ -121,12 +119,12 @@ class nsGIOMimeApp final : public nsIGIOMimeApp {
   NS_DECL_NSIHANDLERAPP
   NS_DECL_NSIGIOMIMEAPP
 
-  explicit nsGIOMimeApp(GAppInfo* aApp) : mApp(aApp) {}
+  explicit nsGIOMimeApp(already_AddRefed<GAppInfo> aApp) : mApp(aApp) {}
 
  private:
-  ~nsGIOMimeApp() { g_object_unref(mApp); }
+  ~nsGIOMimeApp() = default;
 
-  GAppInfo* mApp;
+  RefPtr<GAppInfo> mApp;
 };
 
 NS_IMPL_ISUPPORTS(nsGIOMimeApp, nsIGIOMimeApp, nsIHandlerApp)
@@ -224,12 +222,12 @@ nsGIOMimeApp::LaunchWithURI(nsIURI* aUri,
   // nsPromiseFlatCString flatUri(aUri);
   uris.data = const_cast<char*>(spec.get());
 
-  GError* error = nullptr;
-  gboolean result = g_app_info_launch_uris(mApp, &uris, nullptr, &error);
+  GUniquePtr<GError> error;
+  gboolean result =
+      g_app_info_launch_uris(mApp, &uris, nullptr, getter_Transfers(error));
 
   if (!result) {
     g_warning("Cannot launch application: %s", error->message);
-    g_error_free(error);
     return NS_ERROR_FAILURE;
   }
 
@@ -297,20 +295,17 @@ nsGIOMimeApp::GetSupportedURISchemes(nsIUTF8StringEnumerator** aSchemes) {
 
 NS_IMETHODIMP
 nsGIOMimeApp::SetAsDefaultForMimeType(nsACString const& aMimeType) {
-  char* content_type =
-      g_content_type_from_mime_type(PromiseFlatCString(aMimeType).get());
+  GUniquePtr<char> content_type(
+      g_content_type_from_mime_type(PromiseFlatCString(aMimeType).get()));
   if (!content_type) return NS_ERROR_FAILURE;
-  GError* error = nullptr;
-  g_app_info_set_as_default_for_type(mApp, content_type, &error);
+  GUniquePtr<GError> error;
+  g_app_info_set_as_default_for_type(mApp, content_type.get(),
+                                     getter_Transfers(error));
   if (error) {
     g_warning("Cannot set application as default for MIME type (%s): %s",
               PromiseFlatCString(aMimeType).get(), error->message);
-    g_error_free(error);
-    g_free(content_type);
     return NS_ERROR_FAILURE;
   }
-
-  g_free(content_type);
   return NS_OK;
 }
 /**
@@ -321,21 +316,20 @@ nsGIOMimeApp::SetAsDefaultForMimeType(nsACString const& aMimeType) {
  */
 NS_IMETHODIMP
 nsGIOMimeApp::SetAsDefaultForFileExtensions(nsACString const& fileExts) {
-  GError* error = nullptr;
-  char* extensions = g_strdup(PromiseFlatCString(fileExts).get());
-  char* ext_pos = extensions;
+  GUniquePtr<GError> error;
+  GUniquePtr<char> extensions(g_strdup(PromiseFlatCString(fileExts).get()));
+  char* ext_pos = extensions.get();
   char* space_pos;
 
   while ((space_pos = strchr(ext_pos, ' ')) || (*ext_pos != '\0')) {
     if (space_pos) {
       *space_pos = '\0';
     }
-    g_app_info_set_as_default_for_extension(mApp, ext_pos, &error);
+    g_app_info_set_as_default_for_extension(mApp, ext_pos,
+                                            getter_Transfers(error));
     if (error) {
       g_warning("Cannot set application as default for extension (%s): %s",
                 ext_pos, error->message);
-      g_error_free(error);
-      g_free(extensions);
       return NS_ERROR_FAILURE;
     }
     if (space_pos) {
@@ -344,7 +338,6 @@ nsGIOMimeApp::SetAsDefaultForFileExtensions(nsACString const& fileExts) {
       *ext_pos = '\0';
     }
   }
-  g_free(extensions);
   return NS_OK;
 }
 
@@ -356,15 +349,15 @@ nsGIOMimeApp::SetAsDefaultForFileExtensions(nsACString const& fileExts) {
  */
 NS_IMETHODIMP
 nsGIOMimeApp::SetAsDefaultForURIScheme(nsACString const& aURIScheme) {
-  GError* error = nullptr;
+  GUniquePtr<GError> error;
   nsAutoCString contentType("x-scheme-handler/");
   contentType.Append(aURIScheme);
 
-  g_app_info_set_as_default_for_type(mApp, contentType.get(), &error);
+  g_app_info_set_as_default_for_type(mApp, contentType.get(),
+                                     getter_Transfers(error));
   if (error) {
     g_warning("Cannot set application as default for URI scheme (%s): %s",
               PromiseFlatCString(aURIScheme).get(), error->message);
-    g_error_free(error);
     return NS_ERROR_FAILURE;
   }
 
@@ -380,21 +373,18 @@ nsGIOService::GetMimeTypeFromExtension(const nsACString& aExtension,
   fileExtToUse.Append(aExtension);
 
   gboolean result_uncertain;
-  char* content_type =
-      g_content_type_guess(fileExtToUse.get(), nullptr, 0, &result_uncertain);
-  if (!content_type) return NS_ERROR_FAILURE;
-
-  char* mime_type = g_content_type_get_mime_type(content_type);
-  if (!mime_type) {
-    g_free(content_type);
+  GUniquePtr<char> content_type(
+      g_content_type_guess(fileExtToUse.get(), nullptr, 0, &result_uncertain));
+  if (!content_type) {
     return NS_ERROR_FAILURE;
   }
 
-  aMimeType.Assign(mime_type);
-
-  g_free(mime_type);
-  g_free(content_type);
+  GUniquePtr<char> mime_type(g_content_type_get_mime_type(content_type.get()));
+  if (!mime_type) {
+    return NS_ERROR_FAILURE;
+  }
 
+  aMimeType.Assign(mime_type.get());
   return NS_OK;
 }
 // used in nsGNOMERegistry
@@ -416,19 +406,18 @@ nsGIOService::GetAppForURIScheme(const nsACString& aURIScheme,
       // apps, and we're much better off returning an error here instead.
       return NS_ERROR_FAILURE;
     }
-    nsFlatpakHandlerApp* mozApp = new nsFlatpakHandlerApp();
-    NS_ADDREF(*aApp = mozApp);
+    RefPtr<nsFlatpakHandlerApp> mozApp = new nsFlatpakHandlerApp();
+    mozApp.forget(aApp);
     return NS_OK;
   }
 
-  GAppInfo* app_info = g_app_info_get_default_for_uri_scheme(
-      PromiseFlatCString(aURIScheme).get());
-  if (app_info) {
-    nsGIOMimeApp* mozApp = new nsGIOMimeApp(app_info);
-    NS_ADDREF(*aApp = mozApp);
-  } else {
+  RefPtr<GAppInfo> app_info = dont_AddRef(g_app_info_get_default_for_uri_scheme(
+      PromiseFlatCString(aURIScheme).get()));
+  if (!app_info) {
     return NS_ERROR_FAILURE;
   }
+  RefPtr<nsGIOMimeApp> mozApp = new nsGIOMimeApp(app_info.forget());
+  mozApp.forget(aApp);
   return NS_OK;
 }
 
@@ -456,13 +445,13 @@ nsGIOService::GetAppsForURIScheme(const nsACString& aURIScheme,
     GList* appInfo = appInfoList;
     while (appInfo) {
       nsCOMPtr<nsIGIOMimeApp> mimeApp =
-          new nsGIOMimeApp(G_APP_INFO(appInfo->data));
+          new nsGIOMimeApp(dont_AddRef(G_APP_INFO(appInfo->data)));
       handlersArray->AppendElement(mimeApp);
       appInfo = appInfo->next;
     }
     g_list_free(appInfoList);
   }
-  NS_ADDREF(*aResult = handlersArray);
+  handlersArray.forget(aResult);
   return NS_OK;
 }
 
@@ -474,19 +463,21 @@ nsGIOService::GetAppForMimeType(const nsACString& aMimeType,
   // Flatpak does not reveal installed application to the sandbox,
   // we need to create generic system handler.
   if (widget::ShouldUsePortal(widget::PortalKind::MimeHandler)) {
-    nsFlatpakHandlerApp* mozApp = new nsFlatpakHandlerApp();
-    NS_ADDREF(*aApp = mozApp);
+    RefPtr<nsFlatpakHandlerApp> mozApp = new nsFlatpakHandlerApp();
+    mozApp.forget(aApp);
     return NS_OK;
   }
 
-  char* content_type =
-      g_content_type_from_mime_type(PromiseFlatCString(aMimeType).get());
-  if (!content_type) return NS_ERROR_FAILURE;
+  GUniquePtr<char> content_type(
+      g_content_type_from_mime_type(PromiseFlatCString(aMimeType).get()));
+  if (!content_type) {
+    return NS_ERROR_FAILURE;
+  }
 
   // GIO returns "unknown" appinfo for the application/octet-stream, which is
   // useless. It's better to fallback to create appinfo from file extension
   // later.
-  if (g_content_type_is_unknown(content_type)) {
+  if (g_content_type_is_unknown(content_type.get())) {
     return NS_ERROR_NOT_AVAILABLE;
   }
 
@@ -496,40 +487,37 @@ nsGIOService::GetAppForMimeType(const nsACString& aMimeType,
   // registered as defaults for this type.  Fake it up by just executing
   // xdg-open via gio-launch-desktop (which we do have access to) and letting
   // it figure out which program to execute for this MIME type
-  GAppInfo* app_info = g_app_info_create_from_commandline(
+  RefPtr<GAppInfo> app_info = dont_AddRef(g_app_info_create_from_commandline(
       "/usr/local/bin/xdg-open",
-      nsPrintfCString("System default for %s", content_type).get(),
-      G_APP_INFO_CREATE_NONE, NULL);
+      nsPrintfCString("System default for %s", content_type.get()).get(),
+      G_APP_INFO_CREATE_NONE, NULL));
 #else
-  GAppInfo* app_info = g_app_info_get_default_for_type(content_type, false);
+  RefPtr<GAppInfo> app_info =
+      dont_AddRef(g_app_info_get_default_for_type(content_type.get(), false));
 #endif
-  if (app_info) {
-    nsGIOMimeApp* mozApp = new nsGIOMimeApp(app_info);
-    NS_ADDREF(*aApp = mozApp);
-  } else {
-    g_free(content_type);
+  if (!app_info) {
     return NS_ERROR_FAILURE;
   }
-  g_free(content_type);
+  RefPtr<nsGIOMimeApp> mozApp = new nsGIOMimeApp(app_info.forget());
+  mozApp.forget(aApp);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsGIOService::GetDescriptionForMimeType(const nsACString& aMimeType,
                                         nsACString& aDescription) {
-  char* content_type =
-      g_content_type_from_mime_type(PromiseFlatCString(aMimeType).get());
-  if (!content_type) return NS_ERROR_FAILURE;
-
-  char* desc = g_content_type_get_description(content_type);
-  if (!desc) {
-    g_free(content_type);
+  GUniquePtr<char> content_type(
+      g_content_type_from_mime_type(PromiseFlatCString(aMimeType).get()));
+  if (!content_type) {
     return NS_ERROR_FAILURE;
   }
 
-  aDescription.Assign(desc);
-  g_free(content_type);
-  g_free(desc);
+  GUniquePtr<char> desc(g_content_type_get_description(content_type.get()));
+  if (!desc) {
+    return NS_ERROR_FAILURE;
+  }
+
+  aDescription.Assign(desc.get());
   return NS_OK;
 }
 
@@ -538,11 +526,11 @@ nsGIOService::ShowURI(nsIURI* aURI) {
   nsAutoCString spec;
   nsresult rv = aURI->GetSpec(spec);
   NS_ENSURE_SUCCESS(rv, rv);
-  GError* error = nullptr;
-  if (!g_app_info_launch_default_for_uri(spec.get(), nullptr, &error)) {
+  GUniquePtr<GError> error;
+  if (!g_app_info_launch_default_for_uri(spec.get(), nullptr,
+                                         getter_Transfers(error))) {
     g_warning("Could not launch default application for URI: %s",
               error->message);
-    g_error_free(error);
     return NS_ERROR_FAILURE;
   }
   return NS_OK;
@@ -550,22 +538,17 @@ nsGIOService::ShowURI(nsIURI* aURI) {
 
 NS_IMETHODIMP
 nsGIOService::ShowURIForInput(const nsACString& aUri) {
-  GFile* file = g_file_new_for_commandline_arg(PromiseFlatCString(aUri).get());
-  char* spec = g_file_get_uri(file);
-  nsresult rv = NS_ERROR_FAILURE;
-  GError* error = nullptr;
-
-  g_app_info_launch_default_for_uri(spec, nullptr, &error);
+  RefPtr<GFile> file = dont_AddRef(
+      g_file_new_for_commandline_arg(PromiseFlatCString(aUri).get()));
+  GUniquePtr<char> spec(g_file_get_uri(file));
+  GUniquePtr<GError> error;
+  g_app_info_launch_default_for_uri(spec.get(), nullptr,
+                                    getter_Transfers(error));
   if (error) {
     g_warning("Cannot launch default application: %s", error->message);
-    g_error_free(error);
-  } else {
-    rv = NS_OK;
+    return NS_ERROR_FAILURE;
   }
-  g_object_unref(file);
-  g_free(spec);
-
-  return rv;
+  return NS_OK;
 }
 
 NS_IMETHODIMP
@@ -625,39 +608,37 @@ nsGIOService::OrgFreedesktopFileManager1ShowItems(const nsACString& aPath) {
 NS_IMETHODIMP
 nsGIOService::FindAppFromCommand(nsACString const& aCmd,
                                  nsIGIOMimeApp** aAppInfo) {
-  GAppInfo *app_info = nullptr, *app_info_from_list = nullptr;
+  RefPtr<GAppInfo> app_info;
+
   GList* apps = g_app_info_get_all();
-  GList* apps_p = apps;
 
   // Try to find relevant and existing GAppInfo in all installed application
   // We do this by comparing each GAppInfo's executable with out own
-  while (apps_p) {
-    app_info_from_list = (GAppInfo*)apps_p->data;
+  for (GList* node = apps; node; node = node->next) {
+    RefPtr<GAppInfo> app_info_from_list = dont_AddRef((GAppInfo*)node->data);
+    node->data = nullptr;
     if (!app_info) {
       // If the executable is not absolute, get it's full path
-      char* executable =
-          g_find_program_in_path(g_app_info_get_executable(app_info_from_list));
+      GUniquePtr<char> executable(g_find_program_in_path(
+          g_app_info_get_executable(app_info_from_list)));
 
       if (executable &&
-          strcmp(executable, PromiseFlatCString(aCmd).get()) == 0) {
-        g_object_ref(app_info_from_list);
-        app_info = app_info_from_list;
+          strcmp(executable.get(), PromiseFlatCString(aCmd).get()) == 0) {
+        app_info = std::move(app_info_from_list);
+        // Can't break here because we need to keep iterating to unref the other
+        // nodes.
       }
-      g_free(executable);
     }
-
-    g_object_unref(app_info_from_list);
-    apps_p = apps_p->next;
   }
+
   g_list_free(apps);
-  if (app_info) {
-    nsGIOMimeApp* app = new nsGIOMimeApp(app_info);
-    NS_ADDREF(*aAppInfo = app);
-    return NS_OK;
+  if (!app_info) {
+    *aAppInfo = nullptr;
+    return NS_ERROR_NOT_AVAILABLE;
   }
-
-  *aAppInfo = nullptr;
-  return NS_ERROR_NOT_AVAILABLE;
+  RefPtr<nsGIOMimeApp> app = new nsGIOMimeApp(app_info.forget());
+  app.forget(aAppInfo);
+  return NS_OK;
 }
 
 /**
@@ -673,7 +654,6 @@ NS_IMETHODIMP
 nsGIOService::CreateAppFromCommand(nsACString const& cmd,
                                    nsACString const& appName,
                                    nsIGIOMimeApp** appInfo) {
-  GError* error = nullptr;
   *appInfo = nullptr;
 
   // Using G_APP_INFO_CREATE_SUPPORTS_URIS calling
@@ -683,25 +663,24 @@ nsGIOService::CreateAppFromCommand(nsACString const& cmd,
   nsAutoCString commandWithoutArgs;
   nsresult rv = GetCommandFromCommandline(cmd, commandWithoutArgs);
   NS_ENSURE_SUCCESS(rv, rv);
-  GAppInfo* app_info = g_app_info_create_from_commandline(
+
+  GUniquePtr<GError> error;
+  RefPtr<GAppInfo> app_info = dont_AddRef(g_app_info_create_from_commandline(
       commandWithoutArgs.BeginReading(), PromiseFlatCString(appName).get(),
-      G_APP_INFO_CREATE_SUPPORTS_URIS, &error);
+      G_APP_INFO_CREATE_SUPPORTS_URIS, getter_Transfers(error)));
   if (!app_info) {
     g_warning("Cannot create application info from command: %s",
               error->message);
-    g_error_free(error);
     return NS_ERROR_FAILURE;
   }
 
   // Check if executable exist in path
-  gchar* executableWithFullPath =
-      g_find_program_in_path(commandWithoutArgs.BeginReading());
+  GUniquePtr<gchar> executableWithFullPath(
+      g_find_program_in_path(commandWithoutArgs.BeginReading()));
   if (!executableWithFullPath) {
     return NS_ERROR_FILE_NOT_FOUND;
   }
-  g_free(executableWithFullPath);
-
-  nsGIOMimeApp* mozApp = new nsGIOMimeApp(app_info);
-  NS_ADDREF(*appInfo = mozApp);
+  RefPtr<nsGIOMimeApp> mozApp = new nsGIOMimeApp(app_info.forget());
+  mozApp.forget(appInfo);
   return NS_OK;
 }
diff --git a/widget/gtk/GRefPtr.h b/widget/gtk/GRefPtr.h
index 5b6260f3dbee..aa48467feeeb 100644
--- a/widget/gtk/GRefPtr.h
+++ b/widget/gtk/GRefPtr.h
@@ -12,6 +12,9 @@
 #include <gtk/gtk.h>
 #include "mozilla/RefPtr.h"
 
+// TODO: Remove this (we should use GDBus instead, which is not deprecated).
+#include <dbus/dbus-glib.h>
+
 namespace mozilla {
 
 template <typename T>
@@ -25,12 +28,17 @@ struct GObjectRefPtrTraits {
   struct RefPtrTraits<type_> : public GObjectRefPtrTraits<type_> {};
 
 GOBJECT_TRAITS(GtkWidget)
+GOBJECT_TRAITS(GFile)
 GOBJECT_TRAITS(GMenu)
 GOBJECT_TRAITS(GMenuItem)
 GOBJECT_TRAITS(GSimpleAction)
 GOBJECT_TRAITS(GSimpleActionGroup)
 GOBJECT_TRAITS(GDBusProxy)
+GOBJECT_TRAITS(GAppInfo)
 GOBJECT_TRAITS(GdkDragContext)
+GOBJECT_TRAITS(GdkPixbuf)
+
+GOBJECT_TRAITS(DBusGProxy)
 
 #undef GOBJECT_TRAITS
 
@@ -40,6 +48,30 @@ struct RefPtrTraits<GVariant> {
   static void Release(GVariant* aVariant) { g_variant_unref(aVariant); }
 };
 
+template <>
+struct RefPtrTraits<GHashTable> {
+  static void AddRef(GHashTable* aObject) { g_hash_table_ref(aObject); }
+  static void Release(GHashTable* aObject) { g_hash_table_unref(aObject); }
+};
+
+template <>
+struct RefPtrTraits<GDBusNodeInfo> {
+  static void AddRef(GDBusNodeInfo* aObject) { g_dbus_node_info_ref(aObject); }
+  static void Release(GDBusNodeInfo* aObject) {
+    g_dbus_node_info_unref(aObject);
+  }
+};
+
+template <>
+struct RefPtrTraits<DBusGConnection> {
+  static void AddRef(DBusGConnection* aObject) {
+    dbus_g_connection_ref(aObject);
+  }
+  static void Release(DBusGConnection* aObject) {
+    dbus_g_connection_unref(aObject);
+  }
+};
+
 }  // namespace mozilla
 
 #endif
diff --git a/widget/gtk/MPRISServiceHandler.cpp b/widget/gtk/MPRISServiceHandler.cpp
index 4daf3c8f7e83..ad85082f78c5 100644
--- a/widget/gtk/MPRISServiceHandler.cpp
+++ b/widget/gtk/MPRISServiceHandler.cpp
@@ -12,14 +12,18 @@
 
 #include "MPRISInterfaceDescription.h"
 #include "mozilla/dom/MediaControlUtils.h"
+#include "mozilla/GUniquePtr.h"
+#include "mozilla/UniquePtrExtensions.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/ScopeExit.h"
 #include "mozilla/Sprintf.h"
+#include "nsXULAppAPI.h"
 #include "nsIXULAppInfo.h"
 #include "nsIOutputStream.h"
 #include "nsNetUtil.h"
 #include "nsServiceManagerUtils.h"
 #include "WidgetUtilsGtk.h"
+#include "prio.h"
 
 #define LOGMPRIS(msg, ...)                   \
   MOZ_LOG(gMediaControlLog, LogLevel::Debug, \
@@ -32,19 +36,19 @@ namespace widget {
 // used to form a unique image file name.
 static uint32_t gImageNumber = 0;
 
-static inline Maybe<mozilla::dom::MediaControlKey> GetMediaControlKey(
+static inline Maybe<dom::MediaControlKey> GetMediaControlKey(
     const gchar* aMethodName) {
-  const std::unordered_map<std::string, mozilla::dom::MediaControlKey> map = {
-      {"Raise", mozilla::dom::MediaControlKey::Focus},
-      {"Next", mozilla::dom::MediaControlKey::Nexttrack},
-      {"Previous", mozilla::dom::MediaControlKey::Previoustrack},
-      {"Pause", mozilla::dom::MediaControlKey::Pause},
-      {"PlayPause", mozilla::dom::MediaControlKey::Playpause},
-      {"Stop", mozilla::dom::MediaControlKey::Stop},
-      {"Play", mozilla::dom::MediaControlKey::Play}};
+  const std::unordered_map<std::string, dom::MediaControlKey> map = {
+      {"Raise", dom::MediaControlKey::Focus},
+      {"Next", dom::MediaControlKey::Nexttrack},
+      {"Previous", dom::MediaControlKey::Previoustrack},
+      {"Pause", dom::MediaControlKey::Pause},
+      {"PlayPause", dom::MediaControlKey::Playpause},
+      {"Stop", dom::MediaControlKey::Stop},
+      {"Play", dom::MediaControlKey::Play}};
 
   auto it = map.find(aMethodName);
-  return (it == map.end() ? Nothing() : Some(it->second));
+  return it == map.end() ? Nothing() : Some(it->second);
 }
 
 static void HandleMethodCall(GDBusConnection* aConnection, const gchar* aSender,
@@ -56,7 +60,7 @@ static void HandleMethodCall(GDBusConnection* aConnection, const gchar* aSender,
   MOZ_ASSERT(aUserData);
   MOZ_ASSERT(NS_IsMainThread());
 
-  Maybe<mozilla::dom::MediaControlKey> key = GetMediaControlKey(aMethodName);
+  Maybe<dom::MediaControlKey> key = GetMediaControlKey(aMethodName);
   if (key.isNothing()) {
     g_dbus_method_invocation_return_error(
         aInvocation, G_DBUS_ERROR, G_DBUS_ERROR_NOT_SUPPORTED,
@@ -94,19 +98,18 @@ enum class Property : uint8_t {
   eGetMetadata,
 };
 
-static inline Maybe<mozilla::dom::MediaControlKey> GetPairedKey(
-    Property aProperty) {
+static inline Maybe<dom::MediaControlKey> GetPairedKey(Property aProperty) {
   switch (aProperty) {
     case Property::eCanRaise:
-      return Some(mozilla::dom::MediaControlKey::Focus);
+      return Some(dom::MediaControlKey::Focus);
     case Property::eCanGoNext:
-      return Some(mozilla::dom::MediaControlKey::Nexttrack);
+      return Some(dom::MediaControlKey::Nexttrack);
     case Property::eCanGoPrevious:
-      return Some(mozilla::dom::MediaControlKey::Previoustrack);
+      return Some(dom::MediaControlKey::Previoustrack);
     case Property::eCanPlay:
-      return Some(mozilla::dom::MediaControlKey::Play);
+      return Some(dom::MediaControlKey::Play);
     case Property::eCanPause:
-      return Some(mozilla::dom::MediaControlKey::Pause);
+      return Some(dom::MediaControlKey::Pause);
     default:
       return Nothing();
   }
@@ -179,7 +182,7 @@ static GVariant* HandleGetProperty(GDBusConnection* aConnection,
     case Property::eCanGoPrevious:
     case Property::eCanPlay:
     case Property::eCanPause:
-      Maybe<mozilla::dom::MediaControlKey> key = GetPairedKey(property.value());
+      Maybe<dom::MediaControlKey> key = GetPairedKey(property.value());
       MOZ_ASSERT(key.isSome());
       return g_variant_new_boolean(handler->IsMediaKeySupported(key.value()));
   }
@@ -266,43 +269,37 @@ void MPRISServiceHandler::OnNameLost(GDBusConnection* aConnection,
 
 void MPRISServiceHandler::OnBusAcquired(GDBusConnection* aConnection,
                                         const gchar* aName) {
-  GError* error = nullptr;
+  GUniquePtr<GError> error;
   LOGMPRIS("OnBusAcquired: %s", aName);
 
   mRootRegistrationId = g_dbus_connection_register_object(
       aConnection, DBUS_MPRIS_OBJECT_PATH, mIntrospectionData->interfaces[0],
-      &gInterfaceVTable, this, /* user_data */
-      nullptr,                 /* user_data_free_func */
-      &error);                 /* GError** */
+      &gInterfaceVTable, this,  /* user_data */
+      nullptr,                  /* user_data_free_func */
+      getter_Transfers(error)); /* GError** */
 
   if (mRootRegistrationId == 0) {
     LOGMPRIS("Failed at root registration: %s",
              error ? error->message : "Unknown Error");
-    if (error) {
-      g_error_free(error);
-    }
     return;
   }
 
   mPlayerRegistrationId = g_dbus_connection_register_object(
       aConnection, DBUS_MPRIS_OBJECT_PATH, mIntrospectionData->interfaces[1],
-      &gInterfaceVTable, this, /* user_data */
-      nullptr,                 /* user_data_free_func */
-      &error);                 /* GError** */
+      &gInterfaceVTable, this,  /* user_data */
+      nullptr,                  /* user_data_free_func */
+      getter_Transfers(error)); /* GError** */
 
   if (mPlayerRegistrationId == 0) {
     LOGMPRIS("Failed at object registration: %s",
              error ? error->message : "Unknown Error");
-    if (error) {
-      g_error_free(error);
-    }
   }
 }
 
 bool MPRISServiceHandler::Open() {
   MOZ_ASSERT(!mInitialized);
   MOZ_ASSERT(NS_IsMainThread());
-  GError* error = nullptr;
+  GUniquePtr<GError> error;
   gchar serviceName[256];
 
   InitIdentity();
@@ -315,14 +312,12 @@ bool MPRISServiceHandler::Open() {
                      OnNameAcquiredStatic, OnNameLostStatic, this, nullptr);
 
   /* parse introspection data */
-  mIntrospectionData = g_dbus_node_info_new_for_xml(introspection_xml, &error);
+  mIntrospectionData = dont_AddRef(
+      g_dbus_node_info_new_for_xml(introspection_xml, getter_Transfers(error)));
 
   if (!mIntrospectionData) {
     LOGMPRIS("Failed at parsing XML Interface definition: %s",
              error ? error->message : "Unknown Error");
-    if (error) {
-      g_error_free(error);
-    }
     return false;
   }
 
@@ -330,8 +325,9 @@ bool MPRISServiceHandler::Open() {
   return true;
 }
 
+MPRISServiceHandler::MPRISServiceHandler() = default;
 MPRISServiceHandler::~MPRISServiceHandler() {
-  MOZ_ASSERT(!mInitialized);  // Close hasn't been called!
+  MOZ_ASSERT(!mInitialized, "Close hasn't been called!");
 }
 
 void MPRISServiceHandler::Close() {
@@ -347,9 +343,8 @@ void MPRISServiceHandler::Close() {
   if (mOwnerId != 0) {
     g_bus_unown_name(mOwnerId);
   }
-  if (mIntrospectionData) {
-    g_dbus_node_info_unref(mIntrospectionData);
-  }
+
+  mIntrospectionData = nullptr;
 
   mInitialized = false;
   MediaControlKeySource::Close();
@@ -385,7 +380,7 @@ const char* MPRISServiceHandler::DesktopEntry() const {
   return mDesktopEntry.get();
 }
 
-bool MPRISServiceHandler::PressKey(mozilla::dom::MediaControlKey aKey) const {
+bool MPRISServiceHandler::PressKey(dom::MediaControlKey aKey) const {
   MOZ_ASSERT(mInitialized);
   if (!IsMediaKeySupported(aKey)) {
     LOGMPRIS("%s is not supported", ToMediaControlKeyStr(aKey));
@@ -444,7 +439,7 @@ void MPRISServiceHandler::SetMediaMetadata(
   // 1) MPRIS image is being fetched, and the one in fetching is in the artwork
   // 2) MPRIS image is not being fetched, and the one in use is in the artwork
   if (!mFetchingUrl.IsEmpty()) {
-    if (mozilla::dom::IsImageIn(aMetadata.mArtwork, mFetchingUrl)) {
+    if (dom::IsImageIn(aMetadata.mArtwork, mFetchingUrl)) {
       LOGMPRIS(
           "No need to load MPRIS image. The one being processed is in the "
           "artwork");
@@ -454,7 +449,7 @@ void MPRISServiceHandler::SetMediaMetadata(
       return;
     }
   } else if (!mCurrentImageUrl.IsEmpty()) {
-    if (mozilla::dom::IsImageIn(aMetadata.mArtwork, mCurrentImageUrl)) {
+    if (dom::IsImageIn(aMetadata.mArtwork, mCurrentImageUrl)) {
       LOGMPRIS("No need to load MPRIS image. The one in use is in the artwork");
       SetMediaMetadataInternal(aMetadata, false);
       return;
@@ -508,9 +503,9 @@ void MPRISServiceHandler::LoadImageAtIndex(const size_t aIndex) {
     return;
   }
 
-  const mozilla::dom::MediaImage& image = mMPRISMetadata.mArtwork[aIndex];
+  const dom::MediaImage& image = mMPRISMetadata.mArtwork[aIndex];
 
-  if (!mozilla::dom::IsValidImageUrl(image.mSrc)) {
+  if (!dom::IsValidImageUrl(image.mSrc)) {
     LOGMPRIS("Skip the image with invalid URL. Try next image");
     LoadImageAtIndex(mNextImageIndex++);
     return;
@@ -519,7 +514,7 @@ void MPRISServiceHandler::LoadImageAtIndex(const size_t aIndex) {
   mImageFetchRequest.DisconnectIfExists();
   mFetchingUrl = image.mSrc;
 
-  mImageFetcher = mozilla::MakeUnique<mozilla::dom::FetchImageHelper>(image);
+  mImageFetcher = MakeUnique<dom::FetchImageHelper>(image);
   RefPtr<MPRISServiceHandler> self = this;
   mImageFetcher->FetchImage()
       ->Then(
@@ -532,7 +527,7 @@ void MPRISServiceHandler::LoadImageAtIndex(const size_t aIndex) {
             char* data = nullptr;
             // Only used to hold the image data
             nsCOMPtr<nsIInputStream> inputStream;
-            nsresult rv = mozilla::dom::GetEncodedImageBuffer(
+            nsresult rv = dom::GetEncodedImageBuffer(
                 aImage, mMimeType, getter_AddRefs(inputStream), &size, &data);
             if (NS_FAILED(rv) || !inputStream || size == 0 || !data) {
               LOGMPRIS("Failed to get the image buffer info. Try next image");
@@ -754,9 +749,9 @@ GVariant* MPRISServiceHandler::GetMetadataAsGVariant() const {
   return g_variant_builder_end(&builder);
 }
 
-void MPRISServiceHandler::EmitEvent(mozilla::dom::MediaControlKey aKey) const {
+void MPRISServiceHandler::EmitEvent(dom::MediaControlKey aKey) const {
   for (const auto& listener : mListeners) {
-    listener->OnActionPerformed(mozilla::dom::MediaControlAction(aKey));
+    listener->OnActionPerformed(dom::MediaControlAction(aKey));
   }
 }
 
@@ -764,23 +759,21 @@ struct InterfaceProperty {
   const char* interface;
   const char* property;
 };
-static const std::unordered_map<mozilla::dom::MediaControlKey,
-                                InterfaceProperty>
-    gKeyProperty = {{mozilla::dom::MediaControlKey::Focus,
-                     {DBUS_MPRIS_INTERFACE, "CanRaise"}},
-                    {mozilla::dom::MediaControlKey::Nexttrack,
-                     {DBUS_MPRIS_PLAYER_INTERFACE, "CanGoNext"}},
-                    {mozilla::dom::MediaControlKey::Previoustrack,
-                     {DBUS_MPRIS_PLAYER_INTERFACE, "CanGoPrevious"}},
-                    {mozilla::dom::MediaControlKey::Play,
-                     {DBUS_MPRIS_PLAYER_INTERFACE, "CanPlay"}},
-                    {mozilla::dom::MediaControlKey::Pause,
-                     {DBUS_MPRIS_PLAYER_INTERFACE, "CanPause"}}};
+static const std::unordered_map<dom::MediaControlKey, InterfaceProperty>
+    gKeyProperty = {
+        {dom::MediaControlKey::Focus, {DBUS_MPRIS_INTERFACE, "CanRaise"}},
+        {dom::MediaControlKey::Nexttrack,
+         {DBUS_MPRIS_PLAYER_INTERFACE, "CanGoNext"}},
+        {dom::MediaControlKey::Previoustrack,
+         {DBUS_MPRIS_PLAYER_INTERFACE, "CanGoPrevious"}},
+        {dom::MediaControlKey::Play, {DBUS_MPRIS_PLAYER_INTERFACE, "CanPlay"}},
+        {dom::MediaControlKey::Pause,
+         {DBUS_MPRIS_PLAYER_INTERFACE, "CanPause"}}};
 
 void MPRISServiceHandler::SetSupportedMediaKeys(
     const MediaKeysArray& aSupportedKeys) {
   uint32_t supportedKeys = 0;
-  for (const mozilla::dom::MediaControlKey& key : aSupportedKeys) {
+  for (const dom::MediaControlKey& key : aSupportedKeys) {
     supportedKeys |= GetMediaKeyMask(key);
   }
 
@@ -804,13 +797,12 @@ void MPRISServiceHandler::SetSupportedMediaKeys(
   }
 }
 
-bool MPRISServiceHandler::IsMediaKeySupported(
-    mozilla::dom::MediaControlKey aKey) const {
+bool MPRISServiceHandler::IsMediaKeySupported(dom::MediaControlKey aKey) const {
   return mSupportedKeys & GetMediaKeyMask(aKey);
 }
 
-bool MPRISServiceHandler::EmitSupportedKeyChanged(
-    mozilla::dom::MediaControlKey aKey, bool aSupported) const {
+bool MPRISServiceHandler::EmitSupportedKeyChanged(dom::MediaControlKey aKey,
+                                                  bool aSupported) const {
   auto it = gKeyProperty.find(aKey);
   if (it == gKeyProperty.end()) {
     LOGMPRIS("No property for %s", ToMediaControlKeyStr(aKey));
diff --git a/widget/gtk/MPRISServiceHandler.h b/widget/gtk/MPRISServiceHandler.h
index 6d6c89808846..f2b171c87eea 100644
--- a/widget/gtk/MPRISServiceHandler.h
+++ b/widget/gtk/MPRISServiceHandler.h
@@ -58,11 +58,7 @@ class MPRISServiceHandler final : public dom::MediaControlKeySource {
   // Note that this constructor does NOT initialize the MPRIS Service but only
   // this class. The method Open() is responsible for registering and MAY FAIL.
 
-  // The image format used in MPRIS is based on the mMimeType here. Although
-  // IMAGE_JPEG or IMAGE_BMP are valid types as well but a png image with
-  // transparent background will be converted into a jpeg/bmp file with a
-  // colored background IMAGE_PNG format seems to be the best choice for now.
-  MPRISServiceHandler() : mMimeType(IMAGE_PNG){};
+  MPRISServiceHandler();
   bool Open() override;
   void Close() override;
   bool IsOpened() const override;
@@ -97,13 +93,17 @@ class MPRISServiceHandler final : public dom::MediaControlKeySource {
   guint mRootRegistrationId = 0;
   // This is for the interface org.mpris.MediaPlayer2.Player
   guint mPlayerRegistrationId = 0;
-  GDBusNodeInfo* mIntrospectionData = nullptr;
+  RefPtr<GDBusNodeInfo> mIntrospectionData;
   GDBusConnection* mConnection = nullptr;
   bool mInitialized = false;
   nsAutoCString mIdentity;
   nsAutoCString mDesktopEntry;
 
-  nsCString mMimeType;
+  // The image format used in MPRIS is based on the mMimeType here. Although
+  // IMAGE_JPEG or IMAGE_BMP are valid types as well but a png image with
+  // transparent background will be converted into a jpeg/bmp file with a
+  // colored background IMAGE_PNG format seems to be the best choice for now.
+  nsCString mMimeType{IMAGE_PNG};
 
   // A bitmask indicating what keys are enabled
   uint32_t mSupportedKeys = 0;
@@ -132,9 +132,8 @@ class MPRISServiceHandler final : public dom::MediaControlKeySource {
   nsCOMPtr<nsIFile> mLocalImageFile;
   nsCOMPtr<nsIFile> mLocalImageFolder;
 
-  mozilla::UniquePtr<mozilla::dom::FetchImageHelper> mImageFetcher;
-  mozilla::MozPromiseRequestHolder<mozilla::dom::ImagePromise>
-      mImageFetchRequest;
+  UniquePtr<dom::FetchImageHelper> mImageFetcher;
+  MozPromiseRequestHolder<dom::ImagePromise> mImageFetchRequest;
 
   nsString mFetchingUrl;
   nsString mCurrentImageUrl;
@@ -174,7 +173,7 @@ class MPRISServiceHandler final : public dom::MediaControlKeySource {
   void SetMediaMetadataInternal(const dom::MediaMetadataBase& aMetadata,
                                 bool aClearArtUrl = true);
 
-  bool EmitSupportedKeyChanged(mozilla::dom::MediaControlKey aKey,
+  bool EmitSupportedKeyChanged(dom::MediaControlKey aKey,
                                bool aSupported) const;
 
   bool EmitPropertiesChangedSignal(GVariant* aParameters) const;
diff --git a/widget/gtk/nsAppShell.cpp b/widget/gtk/nsAppShell.cpp
index 8311fc3ef2ee..0b3c0e18d19f 100644
--- a/widget/gtk/nsAppShell.cpp
+++ b/widget/gtk/nsAppShell.cpp
@@ -19,6 +19,7 @@
 #include "mozilla/ProfilerLabels.h"
 #include "mozilla/ProfilerThreadSleep.h"
 #include "mozilla/Unused.h"
+#include "mozilla/GUniquePtr.h"
 #include "mozilla/WidgetUtils.h"
 #include "nsIPowerManagerService.h"
 #ifdef MOZ_ENABLE_DBUS
@@ -37,8 +38,7 @@
 #  include "nsWaylandDisplay.h"
 #endif
 
-using mozilla::LazyLogModule;
-using mozilla::Unused;
+using namespace mozilla;
 using mozilla::widget::HeadlessScreenHelper;
 using mozilla::widget::ScreenHelperGTK;
 using mozilla::widget::ScreenManager;
@@ -195,13 +195,12 @@ static DBusHandlerResult ConnectionSignalFilter(DBusConnection* aConnection,
 // https://github.com/lcp/NetworkManager/blob/240f47c892b4e935a3e92fc09eb15163d1fa28d8/src/nm-sleep-monitor-systemd.c
 // Use login1 to signal sleep and wake notifications.
 void nsAppShell::StartDBusListening() {
-  GError* error = nullptr;
-  mDBusConnection = dbus_g_bus_get(DBUS_BUS_SYSTEM, &error);
+  GUniquePtr<GError> error;
+  mDBusConnection = dbus_g_bus_get(DBUS_BUS_SYSTEM, getter_Transfers(error));
   if (!mDBusConnection) {
     NS_WARNING(nsPrintfCString("gds: Failed to open connection to bus %s\n",
                                error->message)
                    .get());
-    g_error_free(error);
     return;
   }
 
diff --git a/widget/gtk/nsClipboard.cpp b/widget/gtk/nsClipboard.cpp
index a7d58c5665b7..ba9a06a3fdd1 100644
--- a/widget/gtk/nsClipboard.cpp
+++ b/widget/gtk/nsClipboard.cpp
@@ -833,7 +833,7 @@ void nsClipboard::SelectionGetEvent(GtkClipboard* aClipboard,
       return;
     }
 
-    GdkPixbuf* pixbuf = nsImageToPixbuf::ImageToPixbuf(image);
+    RefPtr<GdkPixbuf> pixbuf = nsImageToPixbuf::ImageToPixbuf(image);
     if (!pixbuf) {
       LOGCLIP("    nsImageToPixbuf::ImageToPixbuf() failed!\n");
       return;
@@ -842,7 +842,6 @@ void nsClipboard::SelectionGetEvent(GtkClipboard* aClipboard,
     LOGCLIP("    Setting pixbuf image data as %s\n",
             GUniquePtr<gchar>(gdk_atom_name(selectionTarget)).get());
     gtk_selection_data_set_pixbuf(aSelectionData, pixbuf);
-    g_object_unref(pixbuf);
     return;
   }
 
diff --git a/widget/gtk/nsDragService.cpp b/widget/gtk/nsDragService.cpp
index 68d4c6a83496..93a59e6cd0e0 100644
--- a/widget/gtk/nsDragService.cpp
+++ b/widget/gtk/nsDragService.cpp
@@ -1820,14 +1820,13 @@ void nsDragService::SourceDataGet(GtkWidget* aWidget, GdkDragContext* aContext,
         LOGDRAGSERVICE(("  do_QueryInterface failed\n"));
         return;
       }
-      GdkPixbuf* pixbuf = nsImageToPixbuf::ImageToPixbuf(image);
+      RefPtr<GdkPixbuf> pixbuf = nsImageToPixbuf::ImageToPixbuf(image);
       if (!pixbuf) {
         LOGDRAGSERVICE(("  ImageToPixbuf failed\n"));
         return;
       }
       gtk_selection_data_set_pixbuf(aSelectionData, pixbuf);
       LOGDRAGSERVICE(("  image data set\n"));
-      g_object_unref(pixbuf);
     } else {
       void* tmpData = nullptr;
       uint32_t tmpDataLen = 0;
@@ -1955,12 +1954,11 @@ void nsDragService::SetDragIcon(GdkDragContext* aContext) {
     }
   } else if (surface) {
     if (!SetAlphaPixmap(surface, aContext, offsetX, offsetY, dragRect)) {
-      GdkPixbuf* dragPixbuf = nsImageToPixbuf::SourceSurfaceToPixbuf(
+      RefPtr<GdkPixbuf> dragPixbuf = nsImageToPixbuf::SourceSurfaceToPixbuf(
           surface, dragRect.width, dragRect.height);
       if (dragPixbuf) {
         LOGDRAGSERVICE(("  set drag pixbuf"));
         gtk_drag_set_icon_pixbuf(aContext, dragPixbuf, offsetX, offsetY);
-        g_object_unref(dragPixbuf);
       }
     }
   }
diff --git a/widget/gtk/nsImageToPixbuf.cpp b/widget/gtk/nsImageToPixbuf.cpp
index 57d19e46c210..73094b74ef6e 100644
--- a/widget/gtk/nsImageToPixbuf.cpp
+++ b/widget/gtk/nsImageToPixbuf.cpp
@@ -10,6 +10,8 @@
 #include "imgIContainer.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/RefPtr.h"
+#include "GRefPtr.h"
+#include "nsCOMPtr.h"
 
 using mozilla::gfx::DataSourceSurface;
 using mozilla::gfx::SurfaceFormat;
@@ -20,7 +22,7 @@ inline unsigned char unpremultiply(unsigned char color, unsigned char alpha) {
   return (color * 255 + alpha / 2) / alpha;
 }
 
-GdkPixbuf* nsImageToPixbuf::ImageToPixbuf(
+already_AddRefed<GdkPixbuf> nsImageToPixbuf::ImageToPixbuf(
     imgIContainer* aImage, const mozilla::Maybe<nsIntSize>& aOverrideSize) {
   RefPtr<SourceSurface> surface;
 
@@ -55,15 +57,14 @@ GdkPixbuf* nsImageToPixbuf::ImageToPixbuf(
                                surface->GetSize().height);
 }
 
-GdkPixbuf* nsImageToPixbuf::SourceSurfaceToPixbuf(SourceSurface* aSurface,
-                                                  int32_t aWidth,
-                                                  int32_t aHeight) {
+already_AddRefed<GdkPixbuf> nsImageToPixbuf::SourceSurfaceToPixbuf(
+    SourceSurface* aSurface, int32_t aWidth, int32_t aHeight) {
   MOZ_ASSERT(aWidth <= aSurface->GetSize().width &&
                  aHeight <= aSurface->GetSize().height,
              "Requested rect is bigger than the supplied surface");
 
-  GdkPixbuf* pixbuf =
-      gdk_pixbuf_new(GDK_COLORSPACE_RGB, TRUE, 8, aWidth, aHeight);
+  RefPtr<GdkPixbuf> pixbuf =
+      dont_AddRef(gdk_pixbuf_new(GDK_COLORSPACE_RGB, TRUE, 8, aWidth, aHeight));
   if (!pixbuf) {
     return nullptr;
   }
@@ -116,5 +117,5 @@ GdkPixbuf* nsImageToPixbuf::SourceSurfaceToPixbuf(SourceSurface* aSurface,
 
   dataSurface->Unmap();
 
-  return pixbuf;
+  return pixbuf.forget();
 }
diff --git a/widget/gtk/nsImageToPixbuf.h b/widget/gtk/nsImageToPixbuf.h
index 381827cc1066..500489d7ebaf 100644
--- a/widget/gtk/nsImageToPixbuf.h
+++ b/widget/gtk/nsImageToPixbuf.h
@@ -8,6 +8,7 @@
 
 #include "mozilla/Attributes.h"
 #include "mozilla/Maybe.h"
+#include "mozilla/RefPtr.h"
 #include "nsSize.h"
 
 class imgIContainer;
@@ -23,15 +24,11 @@ class nsImageToPixbuf final {
  public:
   // Friendlier version of ConvertImageToPixbuf for callers inside of
   // widget
-  /**
-   * The return value of all these, if not null, should be
-   * released as needed by the caller using g_object_unref.
-   */
-  static GdkPixbuf* ImageToPixbuf(
+  static already_AddRefed<GdkPixbuf> ImageToPixbuf(
       imgIContainer* aImage,
       const mozilla::Maybe<nsIntSize>& aOverrideSize = mozilla::Nothing());
-  static GdkPixbuf* SourceSurfaceToPixbuf(SourceSurface* aSurface,
-                                          int32_t aWidth, int32_t aHeight);
+  static already_AddRefed<GdkPixbuf> SourceSurfaceToPixbuf(
+      SourceSurface* aSurface, int32_t aWidth, int32_t aHeight);
 
  private:
   ~nsImageToPixbuf() = default;
diff --git a/widget/gtk/nsLookAndFeel.cpp b/widget/gtk/nsLookAndFeel.cpp
index f51ed1bb3d2a..73e64b8c7553 100644
--- a/widget/gtk/nsLookAndFeel.cpp
+++ b/widget/gtk/nsLookAndFeel.cpp
@@ -176,17 +176,16 @@ nsLookAndFeel::nsLookAndFeel() {
       nsWindow::GetSystemGtkWindowDecoration() != nsWindow::GTK_DECORATION_NONE;
 
   if (ShouldUsePortal(PortalKind::Settings)) {
-    GError* error = nullptr;
-    mDBusSettingsProxy = g_dbus_proxy_new_for_bus_sync(
+    GUniquePtr<GError> error;
+    mDBusSettingsProxy = dont_AddRef(g_dbus_proxy_new_for_bus_sync(
         G_BUS_TYPE_SESSION, G_DBUS_PROXY_FLAGS_NONE, nullptr,
         "org.freedesktop.portal.Desktop", "/org/freedesktop/portal/desktop",
-        "org.freedesktop.portal.Settings", nullptr, &error);
+        "org.freedesktop.portal.Settings", nullptr, getter_Transfers(error)));
     if (mDBusSettingsProxy) {
       g_signal_connect(mDBusSettingsProxy, "g-signal",
                        G_CALLBACK(settings_changed_signal_cb), nullptr);
     } else {
       LOGLNF("Can't create DBus proxy for settings: %s\n", error->message);
-      g_error_free(error);
     }
   }
 }
@@ -196,7 +195,7 @@ nsLookAndFeel::~nsLookAndFeel() {
     g_signal_handlers_disconnect_by_func(
         mDBusSettingsProxy, FuncToGpointer(settings_changed_signal_cb),
         nullptr);
-    g_object_unref(mDBusSettingsProxy);
+    mDBusSettingsProxy = nullptr;
   }
   g_signal_handlers_disconnect_by_func(
       gtk_settings_get_default(), FuncToGpointer(settings_changed_cb), nullptr);
@@ -1316,15 +1315,15 @@ Maybe<ColorScheme> nsLookAndFeel::ComputeColorSchemeSetting() {
   if (!mDBusSettingsProxy) {
     return Nothing();
   }
-  GError* error = nullptr;
+  GUniquePtr<GError> error;
   RefPtr<GVariant> variant = dont_AddRef(g_dbus_proxy_call_sync(
       mDBusSettingsProxy, "Read",
       g_variant_new("(ss)", "org.freedesktop.appearance", "color-scheme"),
       G_DBUS_CALL_FLAGS_NONE,
-      StaticPrefs::widget_gtk_settings_portal_timeout_ms(), nullptr, &error));
+      StaticPrefs::widget_gtk_settings_portal_timeout_ms(), nullptr,
+      getter_Transfers(error)));
   if (!variant) {
     LOGLNF("color-scheme query error: %s\n", error->message);
-    g_error_free(error);
     return Nothing();
   }
   LOGLNF("color-scheme query result: %s\n", GVariantToString(variant).get());
diff --git a/widget/gtk/nsLookAndFeel.h b/widget/gtk/nsLookAndFeel.h
index a9a3869a9786..be5caf0dd6f1 100644
--- a/widget/gtk/nsLookAndFeel.h
+++ b/widget/gtk/nsLookAndFeel.h
@@ -150,7 +150,7 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
     return mSystemThemeOverridden ? mAltTheme : mSystemTheme;
   }
 
-  GDBusProxy* mDBusSettingsProxy = nullptr;
+  RefPtr<GDBusProxy> mDBusSettingsProxy;
   mozilla::Maybe<ColorScheme> mColorSchemePreference;
   int32_t mCaretBlinkTime = 0;
   int32_t mCaretBlinkCount = -1;
diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
index 2821666ed072..4f0e7311282c 100644
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -27,6 +27,7 @@
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/Components.h"
+#include "mozilla/GRefPtr.h"
 #include "mozilla/dom/Document.h"
 #include "mozilla/dom/WheelEventBinding.h"
 #include "mozilla/gfx/2D.h"
@@ -3064,7 +3065,7 @@ static GdkCursor* GetCursorForImage(const nsIWidget::Cursor& aCursor,
   }
 
   nsIntSize rasterSize = size * gtkScale;
-  GdkPixbuf* pixbuf =
+  RefPtr<GdkPixbuf> pixbuf =
       nsImageToPixbuf::ImageToPixbuf(aCursor.mContainer, Some(rasterSize));
   if (!pixbuf) {
     return nullptr;
@@ -3074,17 +3075,14 @@ static GdkCursor* GetCursorForImage(const nsIWidget::Cursor& aCursor,
   // is of course not documented anywhere...
   // So add one if there isn't one yet
   if (!gdk_pixbuf_get_has_alpha(pixbuf)) {
-    GdkPixbuf* alphaBuf = gdk_pixbuf_add_alpha(pixbuf, FALSE, 0, 0, 0);
-    g_object_unref(pixbuf);
-    pixbuf = alphaBuf;
-    if (!alphaBuf) {
+    RefPtr<GdkPixbuf> alphaBuf =
+        dont_AddRef(gdk_pixbuf_add_alpha(pixbuf, FALSE, 0, 0, 0));
+    pixbuf = std::move(alphaBuf);
+    if (!pixbuf) {
       return nullptr;
     }
   }
 
-  auto CleanupPixBuf =
-      mozilla::MakeScopeExit([&]() { g_object_unref(pixbuf); });
-
   cairo_surface_t* surface =
       gdk_cairo_surface_create_from_pixbuf(pixbuf, gtkScale, nullptr);
   if (!surface) {
@@ -3092,7 +3090,7 @@ static GdkCursor* GetCursorForImage(const nsIWidget::Cursor& aCursor,
   }
 
   auto CleanupSurface =
-      mozilla::MakeScopeExit([&]() { cairo_surface_destroy(surface); });
+      MakeScopeExit([&]() { cairo_surface_destroy(surface); });
 
   return gdk_cursor_new_from_surface(gdk_display_get_default(), surface,
                                      aCursor.mHotspotX, aCursor.mHotspotY);