[gnome-battery-bench] When battery reports amps not watts, approximate the power

[Owen Taylor <otaylor src gnome org>]

commit 3eb42d2c75dfd44d26de9235e4b7ca11952d612d
Author: Daniel Landau <daniel+gbb landau fi>
Date:   Sun Jan 18 14:39:41 2015 +0200

    When battery reports amps not watts, approximate the power
    
    On systems that report battery capacity in amps, not watts, we can
    approximate the power used by looking at the reported battery voltage.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=747370

 src/power-monitor.c |    9 ++++++++-
 src/power-monitor.h |    1 +
 2 files changed, 9 insertions(+), 1 deletions(-)
---
diff --git a/src/power-monitor.c b/src/power-monitor.c
index 7428d9f..3036815 100644
--- a/src/power-monitor.c
+++ b/src/power-monitor.c
@@ -33,6 +33,7 @@ typedef struct  {
     double charge_full;
     double charge_full_design;
     double capacity_now;
+    double voltage_now;
 } Battery;
 
 typedef struct  {
@@ -79,7 +80,8 @@ gbb_power_state_equal(GbbPowerState *a,
             a->charge_now == b->charge_now &&
             a->charge_full == b->charge_full &&
             a->charge_full_design == b->charge_full_design &&
-            a->capacity_now == b->capacity_now);
+            a->capacity_now == b->capacity_now &&
+            a->voltage_now == b->voltage_now);
 }
 
 void
@@ -158,6 +160,7 @@ battery_poll(Battery *battery)
     if (battery->charge_now >= 0) {
         get_file_contents_double (battery->directory, "charge_full", &battery->charge_full, NULL, NULL);
         get_file_contents_double (battery->directory, "charge_full_design", &battery->charge_full_design, 
NULL, NULL);
+        get_file_contents_double (battery->directory, "voltage_now", &battery->voltage_now, NULL, NULL);
         return;
     }
 
@@ -309,6 +312,7 @@ gbb_power_state_init(GbbPowerState *state)
     state->charge_full = -1.0;
     state->charge_full_design = -1.0;
     state->capacity_now = -1.0;
+    state->voltage_now = -1.0;
 }
 
 GbbPowerState *
@@ -359,6 +363,7 @@ read_state(GbbPowerMonitor *monitor,
         } else if (battery->charge_now >= 0) {
             add_to (&state->charge_now, battery->charge_now);
             add_to (&state->charge_full, battery->charge_full);
+            add_to (&state->voltage_now, battery->voltage_now);
 
             if (battery->charge_full_design >= 0) {
                 if (n_batteries == 0 || state->charge_full_design >= 0)
@@ -444,8 +449,10 @@ gbb_power_statistics_compute (const GbbPowerState   *base,
         }
     } else if (current->charge_now >= 0 && time_elapsed > 0) {
         double charge_used = base->charge_now - current->charge_now;
+        double energy_used = base->charge_now * base->voltage_now - current->charge_now * 
current->voltage_now;
         if (charge_used > 0) {
             statistics->current = 3600 * (charge_used) / time_elapsed;
+            statistics->power = 3600 * (energy_used) / time_elapsed;
             if (base->charge_full >= 0)
                 statistics->battery_life = 3600 * base->charge_full / statistics->current;
             if (base->charge_full_design >= 0)
diff --git a/src/power-monitor.h b/src/power-monitor.h
index 22d4225..efe25cc 100644
--- a/src/power-monitor.h
+++ b/src/power-monitor.h
@@ -25,6 +25,7 @@ struct _GbbPowerState {
     double charge_full;
     double charge_full_design;
     double capacity_now; /* 0 - 1.0 */
+    double voltage_now;
 };
 
 struct _GbbPowerStatistics {