Implement base::PowerMonitor::IsOnBatteryPower() for OSX.

base/power_monitor/power_monitor_device_source_mac.mm

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Implementation based on sample code from
 // http://developer.apple.com/library/mac/#qa/qa1340/_index.html.
 
 #include "base/power_monitor/power_monitor_device_source.h"
 
 #include "base/power_monitor/power_monitor.h"
 #include "base/power_monitor/power_monitor_source.h"
 
 #include <IOKit/IOMessage.h>
+#include <IOKit/ps/IOPSKeys.h>
+#include <IOKit/ps/IOPowerSources.h>
 #include <IOKit/pwr_mgt/IOPMLib.h>
 
 namespace base {
 
 void ProcessPowerEventHelper(PowerMonitorSource::PowerEvent event) {
   PowerMonitorSource::ProcessPowerEvent(event);
 }
 
+bool PowerMonitorDeviceSource::IsOnBatteryPowerImpl() {

[Nico, 2016/09/20 00:05:08]

how often do we poll this? there's a "this changed" observer interface on os x i
think

[DaleCurtis, 2016/09/20 00:15:13]

Doesn't look like it's called very much anywhere. It looks like media/ may be
the biggest user:
https://cs.chromium.org/search/?q=IsOnBatteryPower&type=cs&sq=package:chromium

We're calling it probably every 5 seconds. I look for another interface, but I
think the one you're talking about is used here: 
https://cs.chromium.org/chromium/src/device/battery/battery_status_manager_ma...

Even then it requires repolling all sources on any state change notification. I
guess the state change notification isn't specific enough. Unfortunately this
API also requires a run loop :/

I think I'm going to need that here after all though, since sources are supposed
to send PowerMonitorSource::POWER_STATE_EVENT when the battery status changed.

[Robert Sesek, 2016/09/20 18:19:56]

I do think we should use the IOPSNotificationCreateRunLoopSource() interface
instead. The run loop source could be installed on the main thread without
issue, and when it's received, it could bounce the IOPSCopyPowerSourcesInfo()
work onto a worker pool, and the result could then be cached.
That's my conclusion as well. It looks like the caching may be done for you,
too:
https://cs.chromium.org/chromium/src/base/power_monitor/power_monitor_source....

[DaleCurtis, 2016/09/21 22:49:39]

Done.

+  base::ScopedCFTypeRef<CFTypeRef> info(IOPSCopyPowerSourcesInfo());
+  base::ScopedCFTypeRef<CFArrayRef> power_sources_list(
+      IOPSCopyPowerSourcesList(info));
+
+  const CFIndex count = CFArrayGetCount(power_sources_list);
+  for (CFIndex i = 0; i < count; ++i) {
+    const CFDictionaryRef description = IOPSGetPowerSourceDescription(
+        info, CFArrayGetValueAtIndex(power_sources_list, i));
+    if (!description)
+      continue;
+
+    CFStringRef current_state = base::mac::GetValueFromDictionary<CFStringRef>(
+        description, CFSTR(kIOPSPowerSourceStateKey));
+
+    // We only report "on battery power" if no source is on AC power.
+    if (!CFStringsAreEqual(current_state, CFSTR(kIOPSBatteryPowerValue)))
+      return false;
+  }
+
+  return true;
+}
+
 namespace {
 
 io_connect_t g_system_power_io_port = 0;
 IONotificationPortRef g_notification_port_ref = 0;
 io_object_t g_notifier_object = 0;
 
 void SystemPowerEventCallback(void*,
                               io_service_t service,
                               natural_t message_type,
                               void* message_argument) {
@@ skipping 66 matching lines @@
   // so we close it here.
   IOServiceClose(g_system_power_io_port);
 
   g_system_power_io_port = 0;
 
   // Destroy the notification port allocated by IORegisterForSystemPower.
   IONotificationPortDestroy(g_notification_port_ref);
 }
 
 }  // namespace base