Implement PowerSaveBlocker2 for Linux. Much simpler than the original!

content/browser/power_save_blocker_linux.cc

Index: content/browser/power_save_blocker_linux.cc
===================================================================
--- content/browser/power_save_blocker_linux.cc	(revision 141149)
+++ content/browser/power_save_blocker_linux.cc	(working copy)
@@ -504,3 +504,259 @@
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DBusPowerSaveBlocker::GetInstance()->ApplyBlock(type);
 }
+
+// TODO(mdm): remove from the beginning of the file up to (and including) this
+// line to switch to the new implementation.
+#define PowerSaveBlocker PowerSaveBlocker2
+
+namespace {
+
+enum DBusAPI {
+  kNoAPI,           // Disable. No supported API available.

[sky, 2012/06/08 20:44:41]

enum style in chrome is ALL_CAPS.

[Mike Mammarella, 2012/06/08 20:52:34]

Ah yes, I always forget this difference between the Google style guide and the
Chromium style guide. (In my defense the code I'm replacing did it this way, so
I followed suit.)

+  kGnomeAPI,        // Use the GNOME API. (Supports more features.)
+  kFreeDesktopAPI,  // Use the FreeDesktop API, for KDE4 and XFCE.
+};
+
+// Inhibit flags defined in the org.gnome.SessionManager interface.
+// Can be OR'd together and passed as argument to the Inhibit() method
+// to specify which power management features we want to suspend.
+enum GnomeAPIInhibitFlags {
+  kInhibitLogOut            = 1,
+  kInhibitSwitchUser        = 2,
+  kInhibitSuspendSession    = 4,
+  kInhibitMarkSessionAsIdle = 8
+};
+
+const char kGnomeAPIServiceName[] = "org.gnome.SessionManager";
+const char kGnomeAPIInterfaceName[] = "org.gnome.SessionManager";
+const char kGnomeAPIObjectPath[] = "/org/gnome/SessionManager";
+
+const char kFreeDesktopAPIServiceName[] = "org.freedesktop.PowerManagement";
+const char kFreeDesktopAPIInterfaceName[] =
+    "org.freedesktop.PowerManagement.Inhibit";
+const char kFreeDesktopAPIObjectPath[] =
+    "/org/freedesktop/PowerManagement/Inhibit";
+
+}  // anonymous namespace
+
+namespace content {
+
+class PowerSaveBlocker::Delegate
+    : public base::RefCountedThreadSafe<PowerSaveBlocker::Delegate> {
+ public:
+  // Picks an appropriate D-Bus API to use based on the desktop environment.
+  Delegate(PowerSaveBlockerType type, const std::string& reason);
+
+  // Apply or remove the power save block, respectively. These methods should be
+  // called once each, on the same thread, per instance. They block waiting for
+  // the action to complete (with a timeout); the thread must thus allow IO.
+  void ApplyBlock();
+  void RemoveBlock();
+
+ private:
+  friend class base::RefCountedThreadSafe<Delegate>;
+  ~Delegate() {}
+
+  // If DPMS (the power saving system in X11) is not enabled, then we don't want
+  // to try to disable power saving, since on some desktop environments that may
+  // enable DPMS with very poor default settings (e.g. turning off the display
+  // after only 1 second).
+  static bool DPMSEnabled();
+
+  // Returns an appropriate D-Bus API to use based on the desktop environment.
+  static DBusAPI SelectAPI();
+
+  const PowerSaveBlockerType type_;
+  const std::string reason_;
+  const DBusAPI api_;
+
+  scoped_refptr<dbus::Bus> bus_;
+
+  // The cookie that identifies our inhibit request,
+  // or 0 if there is no active inhibit request.
+  uint32 inhibit_cookie_;
+
+  DISALLOW_COPY_AND_ASSIGN(Delegate);
+};
+
+PowerSaveBlocker::Delegate::Delegate(PowerSaveBlockerType type,
+                                     const std::string& reason)
+    : type_(type), reason_(reason), api_(SelectAPI()) {

[sky, 2012/06/08 20:44:41]

each on its own line, and initialize inhibit_cookie_.

[Mike Mammarella, 2012/06/08 20:52:34]

Done. (Another difference in the style guides!)

+  // We're on the client's thread here, so we don't allocate the dbus::Bus
+  // object yet. We'll do it below in ApplyBlock(), on the FILE thread.
+}
+
+void PowerSaveBlocker::Delegate::ApplyBlock() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  DCHECK(!bus_.get());  // ApplyBlock() should only be called once.
+  if (api_ == kNoAPI)
+    return;
+
+  dbus::Bus::Options options;
+  options.bus_type = dbus::Bus::SESSION;
+  options.connection_type = dbus::Bus::PRIVATE;
+  bus_ = new dbus::Bus(options);
+
+  scoped_refptr<dbus::ObjectProxy> object_proxy;
+  scoped_ptr<dbus::MethodCall> method_call;
+  scoped_ptr<dbus::MessageWriter> message_writer;
+
+  switch (api_) {
+    case kNoAPI:
+      NOTREACHED();  // We return early above.
+      return;
+    case kGnomeAPI:
+      object_proxy = bus_->GetObjectProxy(
+          kGnomeAPIServiceName,
+          dbus::ObjectPath(kGnomeAPIObjectPath));
+      method_call.reset(
+          new dbus::MethodCall(kGnomeAPIInterfaceName, "Inhibit"));
+      message_writer.reset(new dbus::MessageWriter(method_call.get()));
+      // The arguments of the method are:
+      //     app_id:        The application identifier
+      //     toplevel_xid:  The toplevel X window identifier
+      //     reason:        The reason for the inhibit
+      //     flags:         Flags that spefify what should be inhibited
+      message_writer->AppendString(
+          CommandLine::ForCurrentProcess()->GetProgram().value());
+      message_writer->AppendUint32(0);  // should be toplevel_xid
+      message_writer->AppendString(reason_);
+      {
+        uint32 flags = 0;
+        switch (type_) {
+          case kPowerSaveBlockPreventDisplaySleep:
+            flags |= kInhibitMarkSessionAsIdle;
+            flags |= kInhibitSuspendSession;
+            break;
+          case kPowerSaveBlockPreventAppSuspension:
+            flags |= kInhibitSuspendSession;
+            break;
+        }
+        message_writer->AppendUint32(flags);
+      }
+      break;
+    case kFreeDesktopAPI:
+      object_proxy = bus_->GetObjectProxy(
+          kFreeDesktopAPIServiceName,
+          dbus::ObjectPath(kFreeDesktopAPIObjectPath));
+      method_call.reset(
+          new dbus::MethodCall(kFreeDesktopAPIInterfaceName, "Inhibit"));
+      message_writer.reset(new dbus::MessageWriter(method_call.get()));
+      // The arguments of the method are:
+      //     app_id:        The application identifier
+      //     reason:        The reason for the inhibit
+      message_writer->AppendString(
+          CommandLine::ForCurrentProcess()->GetProgram().value());
+      message_writer->AppendString(reason_);
+      break;
+  }
+
+  // We could do this method call asynchronously, but if we did, we'd need to
+  // handle the case where we want to cancel the block before we get a reply.
+  // We're on the FILE thread so it should be OK to block briefly here.
+  scoped_ptr<dbus::Response> response(object_proxy->CallMethodAndBlock(
+      method_call.get(), dbus::ObjectProxy::TIMEOUT_USE_DEFAULT));
+  if (response.get()) {
+    // The method returns an inhibit_cookie, used to uniquely identify
+    // this request. It should be used as an argument to Uninhibit()
+    // in order to remove the request.
+    dbus::MessageReader message_reader(response.get());
+    if (!message_reader.PopUint32(&inhibit_cookie_))
+      LOG(ERROR) << "Invalid Inhibit() response: " << response->ToString();
+  } else {
+    LOG(ERROR) << "No response to Inhibit() request!";
+  }
+}
+
+void PowerSaveBlocker::Delegate::RemoveBlock() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  if (api_ == kNoAPI)
+    return;
+  DCHECK(bus_.get());  // RemoveBlock() should only be called once.
+
+  scoped_refptr<dbus::ObjectProxy> object_proxy;
+  scoped_ptr<dbus::MethodCall> method_call;
+
+  switch (api_) {
+    case kNoAPI:
+      NOTREACHED();  // We return early above.
+      return;
+    case kGnomeAPI:
+      object_proxy = bus_->GetObjectProxy(
+          kGnomeAPIServiceName,
+          dbus::ObjectPath(kGnomeAPIObjectPath));
+      method_call.reset(
+          new dbus::MethodCall(kGnomeAPIInterfaceName, "Uninhibit"));
+      break;
+    case kFreeDesktopAPI:
+      object_proxy = bus_->GetObjectProxy(
+          kFreeDesktopAPIServiceName,
+          dbus::ObjectPath(kFreeDesktopAPIObjectPath));
+      method_call.reset(
+          new dbus::MethodCall(kFreeDesktopAPIInterfaceName, "Uninhibit"));
+      break;
+  }
+
+  dbus::MessageWriter message_writer(method_call.get());
+  message_writer.AppendUint32(inhibit_cookie_);
+  scoped_ptr<dbus::Response> response(object_proxy->CallMethodAndBlock(
+      method_call.get(), dbus::ObjectProxy::TIMEOUT_USE_DEFAULT));
+  if (!response.get())
+    LOG(ERROR) << "No response to Uninhibit() request!";
+  // We don't care about checking the result. We assume it works; we can't
+  // really do anything about it anyway if it fails.
+  inhibit_cookie_ = 0;
+
+  bus_->ShutdownAndBlock();
+  bus_ = NULL;
+}
+
+// static
+bool PowerSaveBlocker::Delegate::DPMSEnabled() {
+  Display* display = base::MessagePumpForUI::GetDefaultXDisplay();
+  BOOL enabled = false;
+  int dummy;
+  if (DPMSQueryExtension(display, &dummy, &dummy) && DPMSCapable(display)) {
+    CARD16 state;
+    DPMSInfo(display, &state, &enabled);
+  }
+  return enabled;
+}
+
+// static
+DBusAPI PowerSaveBlocker::Delegate::SelectAPI() {
+  scoped_ptr<base::Environment> env(base::Environment::Create());
+  switch (base::nix::GetDesktopEnvironment(env.get())) {
+    case base::nix::DESKTOP_ENVIRONMENT_GNOME:
+      if (DPMSEnabled())
+        return kGnomeAPI;
+      break;
+    case base::nix::DESKTOP_ENVIRONMENT_XFCE:
+    case base::nix::DESKTOP_ENVIRONMENT_KDE4:
+      if (DPMSEnabled())
+        return kFreeDesktopAPI;
+      break;
+    case base::nix::DESKTOP_ENVIRONMENT_KDE3:
+    case base::nix::DESKTOP_ENVIRONMENT_OTHER:
+      // Not supported.
+      break;
+  }
+  return kNoAPI;
+}
+
+PowerSaveBlocker::PowerSaveBlocker(
+    PowerSaveBlockerType type, const std::string& reason)
+    : delegate_(new Delegate(type, reason)) {
+  // The thread we use here becomes the origin and D-Bus thread for the D-Bus
+  // library, so we need to use the same thread below in the destructor. It must
+  // be a thread that allows I/O operations.
+  BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
+                          base::Bind(&Delegate::ApplyBlock, delegate_));
+}
+
+PowerSaveBlocker::~PowerSaveBlocker() {
+  BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
+                          base::Bind(&Delegate::RemoveBlock, delegate_));
+}
+
+}  // namespace content