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      1 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "chrome/browser/chromeos/low_battery_observer.h"
      6 
      7 #include "base/utf_string_conversions.h"
      8 #include "chrome/common/time_format.h"
      9 #include "grit/generated_resources.h"
     10 #include "grit/theme_resources.h"
     11 #include "ui/base/l10n/l10n_util.h"
     12 
     13 namespace chromeos {
     14 
     15 LowBatteryObserver::LowBatteryObserver(Profile* profile)
     16   : notification_(profile, "battery.chromeos",
     17                   IDR_NOTIFICATION_LOW_BATTERY,
     18                   l10n_util::GetStringUTF16(IDS_LOW_BATTERY_TITLE)),
     19     remaining_(0) {}
     20 
     21 LowBatteryObserver::~LowBatteryObserver() {
     22   Hide();
     23 }
     24 
     25 void LowBatteryObserver::PowerChanged(PowerLibrary* object) {
     26   const int limit_min = 15;   // Notification will show when remaining number
     27                               // of minutes is <= limit.
     28   const int limit_max = 30;   // Notification will hid when remaining number
     29                               // of minutes is > limit_max.
     30   const int critical = 5;  // Notification will be forced visible if hidden
     31                            // by user when time remaining <= critical.
     32 
     33   base::TimeDelta remaining = object->battery_time_to_empty();
     34   int remaining_minutes = remaining.InMinutes();
     35 
     36   // To simplify the logic - we handle the case of calculating the remaining
     37   // time as if we were on line power.
     38   // remaining time of zero means still calculating, this is denoted by
     39   // base::TimeDelta().
     40   bool line_power = object->line_power_on() || remaining == base::TimeDelta();
     41 
     42   // The urgent flag is used to re-notify the user if the power level
     43   // goes critical. We only want to do this once even if the time remaining
     44   // goes back up (so long as it doesn't go above limit_max.
     45   bool urgent = !line_power &&
     46       (notification_.urgent() || remaining_minutes <= critical);
     47 
     48   // This is a simple state machine with two states and three edges:
     49   // States: visible_, !visible_
     50   // Edges: hide: is visible_ to !visible_ triggered if we transition
     51   //          to line_power, we're calculating our time remaining,
     52   //          or our time remaining has climbed higher than
     53   //          limit_max (either by reduced user an undetected transition
     54   //          to/from line_power).
     55   //        update: is visible_ to _visible triggered when we didn't hide
     56   //          and the minutes remaining changed from what's shown.
     57   //        show: is !visible_ to visible_ triggered when we're on battery,
     58   //          we know the remaining time, and that time is less than limit.
     59 
     60   if (notification_.visible()) {
     61     if (line_power || remaining_minutes > limit_max) {
     62       Hide();
     63     } else if (remaining_minutes != remaining_) {
     64       Show(remaining, urgent);
     65     }
     66   } else {
     67     if (!line_power && remaining_minutes <= limit_min) {
     68       Show(remaining, urgent);
     69     }
     70   }
     71 }
     72 
     73 void LowBatteryObserver::Show(base::TimeDelta remaining, bool urgent) {
     74   notification_.Show(l10n_util::GetStringFUTF16(IDS_LOW_BATTERY_MESSAGE,
     75       TimeFormat::TimeRemaining(remaining)), urgent, true);
     76   remaining_ = remaining.InMinutes();
     77 }
     78 
     79 void LowBatteryObserver::Hide() {
     80   notification_.Hide();
     81 }
     82 
     83 }  // namespace chromeos
     84