From 3312286f425c19406f2eb87e01e622a8e380886c Mon Sep 17 00:00:00 2001
From: stransky <stransky@redhat.com>
Date: Mon, 6 Nov 2023 09:40:32 +0000
Subject: [PATCH] Bug 1762816 [Linux] Watch org.freedesktop.portal.Desktop DBus
 name and get session data only if it's running r=emilio

Don't autostart org.freedesktop.portal.Desktop by g_dbus_proxy_new_for_bus_sync(), that may block Firefox start for 30~ seconds after desktop start.
Use g_bus_watch_name() and get session data only if org.freedesktop.portal.Desktop is available.

Differential Revision: https://phabricator.services.mozilla.com/D192335
---
 widget/gtk/nsLookAndFeel.cpp | 61 +++++++++++++++++++++++++++---------
 widget/gtk/nsLookAndFeel.h   |  4 +++
 2 files changed, 50 insertions(+), 15 deletions(-)

diff --git a/widget/gtk/nsLookAndFeel.cpp b/widget/gtk/nsLookAndFeel.cpp
index d1d86ef519bd..0b7a5d93c055 100644
--- a/widget/gtk/nsLookAndFeel.cpp
+++ b/widget/gtk/nsLookAndFeel.cpp
@@ -134,6 +134,35 @@ static void settings_changed_signal_cb(GDBusProxy* proxy, gchar* sender_name,
   }
 }
 
+void nsLookAndFeel::WatchDBus() {
+  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, getter_Transfers(error)));
+  if (mDBusSettingsProxy) {
+    g_signal_connect(mDBusSettingsProxy, "g-signal",
+                     G_CALLBACK(settings_changed_signal_cb), this);
+  } else {
+    LOGLNF("Can't create DBus proxy for settings: %s\n", error->message);
+    return;
+  }
+
+  // DBus interface was started after L&F init so we need to load
+  // our settings from DBus explicitly.
+  if (!sIgnoreChangedSettings) {
+    OnColorSchemeSettingChanged();
+  }
+}
+
+void nsLookAndFeel::UnwatchDBus() {
+  if (mDBusSettingsProxy) {
+    g_signal_handlers_disconnect_by_func(
+        mDBusSettingsProxy, FuncToGpointer(settings_changed_signal_cb), this);
+    mDBusSettingsProxy = nullptr;
+  }
+}
+
 nsLookAndFeel::nsLookAndFeel() {
   static constexpr nsLiteralCString kObservedSettings[] = {
       // Affects system font sizes.
@@ -172,27 +201,29 @@ nsLookAndFeel::nsLookAndFeel() {
       nsWindow::GetSystemGtkWindowDecoration() != nsWindow::GTK_DECORATION_NONE;
 
   if (ShouldUsePortal(PortalKind::Settings)) {
-    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, getter_Transfers(error)));
-    if (mDBusSettingsProxy) {
-      g_signal_connect(mDBusSettingsProxy, "g-signal",
-                       G_CALLBACK(settings_changed_signal_cb), this);
-    } else {
-      LOGLNF("Can't create DBus proxy for settings: %s\n", error->message);
-    }
+    mDBusID = g_bus_watch_name(
+        G_BUS_TYPE_SESSION, "org.freedesktop.portal.Desktop",
+        G_BUS_NAME_WATCHER_FLAGS_AUTO_START,
+        [](GDBusConnection*, const gchar*, const gchar*,
+           gpointer data) -> void {
+          auto* lnf = static_cast<nsLookAndFeel*>(data);
+          lnf->WatchDBus();
+        },
+        [](GDBusConnection*, const gchar*, gpointer data) -> void {
+          auto* lnf = static_cast<nsLookAndFeel*>(data);
+          lnf->UnwatchDBus();
+        },
+        this, nullptr);
   }
 }
 
 nsLookAndFeel::~nsLookAndFeel() {
   ClearRoundedCornerProvider();
-  if (mDBusSettingsProxy) {
-    g_signal_handlers_disconnect_by_func(
-        mDBusSettingsProxy, FuncToGpointer(settings_changed_signal_cb), this);
-    mDBusSettingsProxy = nullptr;
+  if (mDBusID) {
+    g_bus_unwatch_name(mDBusID);
+    mDBusID = 0;
   }
+  UnwatchDBus();
   g_signal_handlers_disconnect_by_func(
       gtk_settings_get_default(), FuncToGpointer(settings_changed_cb), nullptr);
 }
diff --git a/widget/gtk/nsLookAndFeel.h b/widget/gtk/nsLookAndFeel.h
index e13c619e6634..48400b31c042 100644
--- a/widget/gtk/nsLookAndFeel.h
+++ b/widget/gtk/nsLookAndFeel.h
@@ -53,6 +53,9 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
   static bool ShouldHonorThemeScrollbarColors();
   mozilla::Maybe<ColorScheme> ComputeColorSchemeSetting();
 
+  void WatchDBus();
+  void UnwatchDBus();
+
   enum class ThemeFamily : uint8_t {
     // Adwaita, the default GTK theme.
     Adwaita,
@@ -160,6 +163,7 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
     return mSystemThemeOverridden ? mAltTheme : mSystemTheme;
   }
 
+  uint32_t mDBusID = 0;
   RefPtr<GDBusProxy> mDBusSettingsProxy;
   mozilla::Maybe<ColorScheme> mColorSchemePreference;
   int32_t mCaretBlinkTime = 0;