Prefer to use ubuntu-platform-hardware-api for wakeups when possible s.t. user-defined alarms/appointments can wake up the phone from sleep to give a snap decision. Fixes: 1299916

9 files changed, 607 insertions, 135 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 9bc22f2..ffa1523 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -7,30 +7,37 @@ SET (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -g ${CXX_WARNING_ARGS} ${GCO
 add_definitions (-DTIMEZONE_FILE="/etc/timezone"
                  -DG_LOG_DOMAIN="Indicator-Datetime")
 
-add_library (${SERVICE_LIB} STATIC
-             actions.cpp
-             actions-live.cpp
-             appointment.cpp
-             clock.cpp
-             clock-live.cpp
-             clock-watcher.cpp
-             date-time.cpp
-             engine-eds.cpp
-             exporter.cpp
-             formatter.cpp
-             formatter-desktop.cpp
-             locations.cpp
-             locations-settings.cpp
-             menu.cpp
-             planner-month.cpp
-             planner-range.cpp
-             planner-upcoming.cpp
-             settings-live.cpp
-             snap.cpp
-             timezone-file.cpp
-             timezone-geoclue.cpp
-             timezones-live.cpp
-             utils.c)
+set (SERVICE_SOURCES
+     actions.cpp
+     actions-live.cpp
+     alarm-queue-simple.cpp
+     appointment.cpp
+     clock.cpp
+     clock-live.cpp
+     date-time.cpp
+     engine-eds.cpp
+     exporter.cpp
+     formatter.cpp
+     formatter-desktop.cpp
+     locations.cpp
+     locations-settings.cpp
+     menu.cpp
+     planner-month.cpp
+     planner-range.cpp
+     planner-upcoming.cpp
+     settings-live.cpp
+     snap.cpp
+     timezone-file.cpp
+     timezone-geoclue.cpp
+     timezones-live.cpp
+     utils.c
+     wakeup-timer-mainloop.cpp)
+
+if (HAVE_UBUNTU_HW_ALARM_H)
+  set (SERVICE_SOURCES ${SERVICE_SOURCES} wakeup-timer-uha.cpp)
+endif ()
+
+add_library (${SERVICE_LIB} STATIC ${SERVICE_SOURCES})
 include_directories (${CMAKE_SOURCE_DIR})
 link_directories (${SERVICE_DEPS_LIBRARY_DIRS})
 
diff --git a/src/alarm-queue-simple.cpp b/src/alarm-queue-simple.cpp
new file mode 100644
index 0000000..fa6c0bc
--- /dev/null
+++ b/src/alarm-queue-simple.cpp
@@ -0,0 +1,159 @@
+/*
+ * Copyright 2014 Canonical Ltd.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 3, as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranties of
+ * MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors:
+ *   Charles Kerr <charles.kerr@canonical.com>
+ */
+
+#include <datetime/alarm-queue-simple.h>
+
+#include <cmath>
+
+namespace unity {
+namespace indicator {
+namespace datetime {
+
+/***
+****  Public API
+***/
+
+SimpleAlarmQueue::SimpleAlarmQueue(const std::shared_ptr<Clock>& clock,
+                                   const std::shared_ptr<Planner>& planner,
+                                   const std::shared_ptr<WakeupTimer>& timer):
+    m_clock(clock),
+    m_planner(planner),
+    m_timer(timer),
+    m_datetime(clock->localtime())
+{
+    m_planner->appointments().changed().connect([this](const std::vector<Appointment>&){
+        g_debug("AlarmQueue %p calling requeue() due to appointments changed", this);
+        requeue();
+    });
+
+    m_clock->minute_changed.connect([=]{
+        const auto now = m_clock->localtime();
+        constexpr auto skew_threshold_usec = int64_t{90} * G_USEC_PER_SEC;
+        const bool clock_jumped = std::abs(now - m_datetime) > skew_threshold_usec;
+        m_datetime = now;
+        if (clock_jumped) {
+            g_debug("AlarmQueue %p calling requeue() due to clock skew", this);
+            requeue();
+        }
+    });
+
+    m_timer->timeout().connect([this](){
+        g_debug("AlarmQueue %p calling requeue() due to timeout", this);
+        requeue();
+    });
+
+    requeue();
+}
+
+SimpleAlarmQueue::~SimpleAlarmQueue()
+{
+}
+
+core::Signal<const Appointment&>& SimpleAlarmQueue::alarm_reached()
+{
+    return m_alarm_reached;
+}
+
+/***
+****
+***/
+
+void SimpleAlarmQueue::requeue()
+{
+    // kick any current alarms
+    for (auto current : find_current_alarms())
+    {
+        const std::pair<std::string,DateTime> trig {current.uid, current.begin};
+        m_triggered.insert(trig);
+        m_alarm_reached(current);
+    }
+
+    // idle until the next alarm
+    Appointment next;
+    if (find_next_alarm(next))
+    {
+        g_debug ("setting timer to wake up for next appointment '%s' at %s", 
+                 next.summary.c_str(),
+                 next.begin.format("%F %T").c_str());
+
+        m_timer->set_wakeup_time(next.begin);
+    }
+}
+
+// find the next alarm that will kick now or in the future
+bool SimpleAlarmQueue::find_next_alarm(Appointment& setme) const
+{
+    bool found = false;
+    Appointment tmp;
+    const auto now = m_clock->localtime();
+    const auto beginning_of_minute = now.add_full (0, 0, 0, 0, 0, -now.seconds());
+
+    const auto appointments = m_planner->appointments().get();
+    g_debug ("planner has %zu appointments in it", (size_t)appointments.size());
+
+    for(const auto& walk : appointments)
+    {
+        const std::pair<std::string,DateTime> trig {walk.uid, walk.begin};
+        if (m_triggered.count(trig))
+            continue;
+
+        if (walk.begin < beginning_of_minute) // has this one already passed?
+            continue;
+
+        if (found && (tmp.begin < walk.begin)) // do we already have a better match?
+            continue;
+
+        tmp = walk;
+        found = true;
+    }
+
+    if (found)
+      setme = tmp;
+
+    return found;
+}
+
+// find the alarm(s) that should kick right now
+std::vector<Appointment> SimpleAlarmQueue::find_current_alarms() const
+{
+    std::vector<Appointment> appointments;
+
+    const auto now = m_clock->localtime();
+
+    for(const auto& walk : m_planner->appointments().get())
+    {
+        const std::pair<std::string,DateTime> trig {walk.uid, walk.begin};
+        if (m_triggered.count(trig)) // did we already use this one?
+            continue;
+        if (!DateTime::is_same_minute(now, walk.begin))
+            continue;
+
+        appointments.push_back(walk);
+    }
+
+    return appointments;
+}
+
+/***
+****
+***/
+
+} // namespace datetime
+} // namespace indicator
+} // namespace unity
diff --git a/src/clock-watcher.cpp b/src/clock-watcher.cpp
deleted file mode 100644
index 5da66c8..0000000
--- a/src/clock-watcher.cpp
+++ /dev/null
@@ -1,81 +0,0 @@
-/*
- * Copyright 2014 Canonical Ltd.
- *
- * This program is free software: you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 3, as published
- * by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranties of
- * MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
- * PURPOSE.  See the GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- * Authors:
- *   Charles Kerr <charles.kerr@canonical.com>
- */
-
-#include <datetime/clock-watcher.h>
-
-namespace unity {
-namespace indicator {
-namespace datetime {
-
-/***
-****
-***/
-
-ClockWatcherImpl::ClockWatcherImpl(const std::shared_ptr<Clock>& clock,
-                                   const std::shared_ptr<UpcomingPlanner>& upcoming_planner):
-    m_clock(clock),
-    m_upcoming_planner(upcoming_planner)
-{
-    m_clock->date_changed.connect([this](){
-        const auto now = m_clock->localtime();
-        g_debug("ClockWatcher %p refretching appointments due to date change: %s", this, now.format("%F %T").c_str());
-        m_upcoming_planner->date().set(now);
-    });
-
-    m_clock->minute_changed.connect([this](){
-        g_debug("ClockWatcher %p calling pulse() due to clock minute_changed", this);
-        pulse();
-    });
-
-    m_upcoming_planner->appointments().changed().connect([this](const std::vector<Appointment>&){
-        g_debug("ClockWatcher %p calling pulse() due to appointments changed", this);
-        pulse();
-    });
-
-    pulse();
-}
-
-core::Signal<const Appointment&>& ClockWatcherImpl::alarm_reached()
-{
-    return m_alarm_reached;
-}
-
-void ClockWatcherImpl::pulse()
-{
-    const auto now = m_clock->localtime();
-
-    for(const auto& appointment : m_upcoming_planner->appointments().get())
-    {
-        if (m_triggered.count(appointment.uid))
-            continue;
-        if (!DateTime::is_same_minute(now, appointment.begin))
-            continue;
-
-        m_triggered.insert(appointment.uid);
-        m_alarm_reached(appointment);
-    }
-}
-
-/***
-****
-***/
-
-} // namespace datetime
-} // namespace indicator
-} // namespace unity
diff --git a/src/date-time.cpp b/src/date-time.cpp
index a1c1d1b..a139ea9 100644
--- a/src/date-time.cpp
+++ b/src/date-time.cpp
@@ -174,6 +174,11 @@ bool DateTime::operator==(const DateTime& that) const
     return g_date_time_compare(get(), that.get()) == 0;
 }
 
+int64_t DateTime::operator- (const DateTime& that) const
+{
+    return g_date_time_difference(get(), that.get());
+}
+
 bool DateTime::is_same_day(const DateTime& a, const DateTime& b)
 {
     // it's meaningless to compare uninitialized dates
diff --git a/src/engine-eds.cpp b/src/engine-eds.cpp
index da93206..1949193 100644
--- a/src/engine-eds.cpp
+++ b/src/engine-eds.cpp
@@ -418,6 +418,14 @@ private:
             auto status = ICAL_STATUS_NONE;
             e_cal_component_get_status(component, &status);
 
+            const auto begin_dt = DateTime(begin);
+            const auto end_dt = DateTime(end);
+            g_debug ("got appointment from %s to %s, uid %s status %d",
+                     begin_dt.format("%F %T").c_str(),
+                     end_dt.format("%F %T").c_str(),
+                     uid,
+                     (int)status);
+
             if ((uid != nullptr) &&
                 (status != ICAL_STATUS_COMPLETED) &&
                 (status != ICAL_STATUS_CANCELLED))
@@ -430,8 +438,8 @@ private:
                 if (text.value)
                     appointment.summary = text.value;
 
-                appointment.begin = DateTime(begin);
-                appointment.end = DateTime(end);
+                appointment.begin = begin_dt;
+                appointment.end = end_dt;
                 appointment.color = subtask->color;
                 appointment.uid = uid;
 
diff --git a/src/main.cpp b/src/main.cpp
index c7b35e5..079fe35 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -18,8 +18,8 @@
  */
 
 #include <datetime/actions-live.h>
+#include <datetime/alarm-queue-simple.h>
 #include <datetime/clock.h>
-#include <datetime/clock-watcher.h>
 #include <datetime/engine-mock.h>
 #include <datetime/engine-eds.h>
 #include <datetime/exporter.h>
@@ -31,6 +31,11 @@
 #include <datetime/state.h>
 #include <datetime/timezone-file.h>
 #include <datetime/timezones-live.h>
+#include <datetime/wakeup-timer-mainloop.h>
+
+#ifdef HAVE_UBUNTU_HW_ALARM_H
+  #include <datetime/wakeup-timer-uha.h>
+#endif
 
 #include <glib/gi18n.h> // bindtextdomain()
 #include <gio/gio.h>
@@ -42,6 +47,81 @@
 
 using namespace unity::indicator::datetime;
 
+namespace
+{
+    std::shared_ptr<Engine> create_engine()
+    {
+        std::shared_ptr<Engine> engine;
+
+        // we don't show appointments in the greeter,
+        // so no need to connect to EDS there...
+        if (!g_strcmp0("lightdm", g_get_user_name()))
+            engine.reset(new MockEngine);
+        else
+            engine.reset(new EdsEngine);
+
+        return engine;
+    }
+
+    std::shared_ptr<WakeupTimer> create_wakeup_timer(const std::shared_ptr<Clock>& clock)
+    {
+        std::shared_ptr<WakeupTimer> wakeup_timer;
+
+#ifdef HAVE_UBUNTU_HW_ALARM_H
+        if (UhaWakeupTimer::is_supported()) // prefer to use the platform API
+            wakeup_timer = std::make_shared<UhaWakeupTimer>(clock);
+        else
+#endif
+            wakeup_timer = std::make_shared<MainloopWakeupTimer>(clock);
+
+        return wakeup_timer;
+    }
+
+    std::shared_ptr<State> create_state(const std::shared_ptr<Engine>& engine,
+                                        const std::shared_ptr<Timezone>& tz)
+    {
+        // create the live objects
+        auto live_settings = std::make_shared<LiveSettings>();
+        auto live_timezones = std::make_shared<LiveTimezones>(live_settings, TIMEZONE_FILE);
+        auto live_clock = std::make_shared<LiveClock>(live_timezones);
+
+        // create a full-month planner currently pointing to the current month
+        const auto now = live_clock->localtime();
+        auto range_planner = std::make_shared<SimpleRangePlanner>(engine, tz);
+        auto calendar_month = std::make_shared<MonthPlanner>(range_planner, now);
+
+        // create an upcoming-events planner currently pointing to the current date
+        range_planner = std::make_shared<SimpleRangePlanner>(engine, tz);
+        auto calendar_upcoming = std::make_shared<UpcomingPlanner>(range_planner, now);
+
+        // create the state
+        auto state = std::make_shared<State>();
+        state->settings = live_settings;
+        state->clock = live_clock;
+        state->locations = std::make_shared<SettingsLocations>(live_settings, live_timezones);
+        state->calendar_month = calendar_month;
+        state->calendar_upcoming = calendar_upcoming;
+        return state;
+    }
+
+    std::shared_ptr<AlarmQueue> create_simple_alarm_queue(const std::shared_ptr<Clock>& clock,
+                                                          const std::shared_ptr<Engine>& engine,
+                                                          const std::shared_ptr<Timezone>& tz)
+    {
+        // create an upcoming-events planner that =always= tracks the clock's date
+        auto range_planner = std::make_shared<SimpleRangePlanner>(engine, tz);
+        auto upcoming_planner = std::make_shared<UpcomingPlanner>(range_planner, clock->localtime());
+        clock->date_changed.connect([clock,upcoming_planner](){
+            const auto now = clock->localtime();
+            g_debug("refretching appointments due to date change: %s", now.format("%F %T").c_str());
+            upcoming_planner->date().set(now);
+        });
+
+        auto wakeup_timer = create_wakeup_timer(clock);
+        return std::make_shared<SimpleAlarmQueue>(clock, upcoming_planner, wakeup_timer);
+    }
+}
+
 int
 main(int /*argc*/, char** /*argv*/)
 {
@@ -54,35 +134,16 @@ main(int /*argc*/, char** /*argv*/)
     bindtextdomain(GETTEXT_PACKAGE, GNOMELOCALEDIR);
     textdomain(GETTEXT_PACKAGE);
 
-    // we don't show appointments in the greeter,
-    // so no need to connect to EDS there...
-    std::shared_ptr<Engine> engine;
-    if (!g_strcmp0("lightdm", g_get_user_name()))
-        engine.reset(new MockEngine);
-    else
-        engine.reset(new EdsEngine);
-
-    // build the state, actions, and menufactory
-    std::shared_ptr<State> state(new State);
-    std::shared_ptr<Settings> live_settings(new LiveSettings);
-    std::shared_ptr<Timezones> live_timezones(new LiveTimezones(live_settings, TIMEZONE_FILE));
-    std::shared_ptr<Clock> live_clock(new LiveClock(live_timezones));
-    std::shared_ptr<Timezone> file_timezone(new FileTimezone(TIMEZONE_FILE));
-    const auto now = live_clock->localtime();
-    state->settings = live_settings;
-    state->clock = live_clock;
-    state->locations.reset(new SettingsLocations(live_settings, live_timezones));
-    auto calendar_month = new MonthPlanner(std::shared_ptr<RangePlanner>(new SimpleRangePlanner(engine, file_timezone)), now);
-    state->calendar_month.reset(calendar_month);
-    state->calendar_upcoming.reset(new UpcomingPlanner(std::shared_ptr<RangePlanner>(new SimpleRangePlanner(engine, file_timezone)), now));
-    std::shared_ptr<Actions> actions(new LiveActions(state));
+    auto engine = create_engine();
+    auto timezone = std::make_shared<FileTimezone>(TIMEZONE_FILE);
+    auto state = create_state(engine, timezone);
+    auto actions = std::make_shared<LiveActions>(state);
     MenuFactory factory(actions, state);
 
-    // snap decisions
-    std::shared_ptr<UpcomingPlanner> upcoming_planner(new UpcomingPlanner(std::shared_ptr<RangePlanner>(new SimpleRangePlanner(engine, file_timezone)), now));
-    ClockWatcherImpl clock_watcher(live_clock, upcoming_planner);
+    // set up the snap decisions
     Snap snap;
-    clock_watcher.alarm_reached().connect([&snap](const Appointment& appt){
+    auto alarm_queue = create_simple_alarm_queue(state->clock, engine, timezone);
+    alarm_queue->alarm_reached().connect([&snap](const Appointment& appt){
         auto snap_show = [](const Appointment& a){
             const char* url;
             if(!a.url.empty())
diff --git a/src/planner-range.cpp b/src/planner-range.cpp
index 93946e0..41b0f56 100644
--- a/src/planner-range.cpp
+++ b/src/planner-range.cpp
@@ -34,7 +34,7 @@ SimpleRangePlanner::SimpleRangePlanner(const std::shared_ptr<Engine>& engine,
     m_range(std::pair<DateTime,DateTime>(DateTime::NowLocal(), DateTime::NowLocal()))
 {
     engine->changed().connect([this](){
-        g_debug("RangePlanner %p rebuilding soon because Engine %p emitted 'changed' signal%p", this, m_engine.get());
+        g_debug("RangePlanner %p rebuilding soon because Engine %p emitted 'changed' signal", this, m_engine.get());
         rebuild_soon();
     });
 
diff --git a/src/wakeup-timer-mainloop.cpp b/src/wakeup-timer-mainloop.cpp
new file mode 100644
index 0000000..4f99c8c
--- /dev/null
+++ b/src/wakeup-timer-mainloop.cpp
@@ -0,0 +1,138 @@
+/*
+ * Copyright 2014 Canonical Ltd.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 3, as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranties of
+ * MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors:
+ *   Charles Kerr <charles.kerr@canonical.com>
+ */
+
+#include <datetime/wakeup-timer-mainloop.h>
+
+#include <glib.h>
+
+#include <cstdlib> // abs()
+
+namespace unity {
+namespace indicator {
+namespace datetime {
+
+/***
+****
+***/
+
+class MainloopWakeupTimer::Impl
+{
+
+public:
+
+    Impl(const std::shared_ptr<Clock>& clock):
+        m_clock(clock)
+    {
+    }
+
+    ~Impl()
+    {
+        cancel_timer();
+    }
+
+    void set_wakeup_time(const DateTime& d)
+    {
+        m_wakeup_time = d;
+
+        rebuild_timer();
+    }
+
+    core::Signal<>& timeout() { return m_timeout; }
+
+private:
+
+    void rebuild_timer()
+    {
+        cancel_timer();
+
+        g_return_if_fail(m_wakeup_time.is_set());
+
+        const auto now = m_clock->localtime();
+        const auto difference_usec = g_date_time_difference(m_wakeup_time.get(), now.get());
+        const guint interval_msec = std::abs(difference_usec) / 1000u;
+        g_debug("%s setting wakeup timer to kick at %s, which is in %zu seconds",
+                G_STRFUNC,
+                m_wakeup_time.format("%F %T").c_str(),
+                size_t{interval_msec/1000});
+
+        m_timeout_tag = g_timeout_add_full(G_PRIORITY_HIGH,
+                                           interval_msec,
+                                           on_timeout,
+                                           this,
+                                           nullptr);
+    }
+
+    static gboolean on_timeout(gpointer gself)
+    {
+        g_debug("%s %s", G_STRLOC, G_STRFUNC);
+        static_cast<Impl*>(gself)->on_timeout();
+        return G_SOURCE_REMOVE;
+    }
+
+    void on_timeout()
+    {
+        cancel_timer();
+        m_timeout();
+    }
+
+    void cancel_timer()
+    {
+        if (m_timeout_tag != 0)
+        {
+            g_source_remove(m_timeout_tag);
+            m_timeout_tag = 0;
+        }
+    }
+
+    core::Signal<> m_timeout;
+    const std::shared_ptr<Clock>& m_clock;
+    guint m_timeout_tag = 0;
+    DateTime m_wakeup_time;
+};
+
+/***
+****
+***/
+
+MainloopWakeupTimer::MainloopWakeupTimer(const std::shared_ptr<Clock>& clock):
+    p(new Impl(clock))
+{
+}
+
+MainloopWakeupTimer::~MainloopWakeupTimer()
+{
+}
+
+void MainloopWakeupTimer::set_wakeup_time(const DateTime& d)
+{
+    p->set_wakeup_time(d);
+}
+
+core::Signal<>& MainloopWakeupTimer::timeout()
+{
+    return p->timeout();
+}
+
+/***
+****
+***/
+
+} // namespace datetime
+} // namespace indicator
+} // namespace unity
diff --git a/src/wakeup-timer-uha.cpp b/src/wakeup-timer-uha.cpp
new file mode 100644
index 0000000..437eda2
--- /dev/null
+++ b/src/wakeup-timer-uha.cpp
@@ -0,0 +1,175 @@
+/*
+ * Copyright 2014 Canonical Ltd.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 3, as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranties of
+ * MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors:
+ *   Charles Kerr <charles.kerr@canonical.com>
+ */
+
+#include <datetime/wakeup-timer-uha.h>
+
+#include <ubuntu/hardware/alarm.h>
+
+#include <glib.h>
+
+#include <unistd.h>
+
+#include <ctime> // struct timespec
+#include <mutex>
+#include <thread>
+
+namespace unity {
+namespace indicator {
+namespace datetime {
+
+/***
+****
+***/
+
+class UhaWakeupTimer::Impl
+{
+
+public:
+
+    Impl(const std::shared_ptr<Clock>& clock):
+        m_clock(clock),
+        m_hardware_alarm(u_hardware_alarm_create())
+    {
+        // fire up a worker thread that initially just sleeps
+        set_wakeup_time_to_the_distant_future();
+        m_thread = std::move(std::thread([&](){threadfunc();}));
+    }
+
+    ~Impl()
+    {
+        // tell the worker thread to wake up and exit
+        m_yielding = true;
+        set_wakeup_time(m_clock->localtime().add_full(0,0,0,0,0,0.1));
+
+        // wait for it to happen
+        if (m_thread.joinable())
+            m_thread.join();
+
+        g_idle_remove_by_data(this);
+
+        u_hardware_alarm_unref(m_hardware_alarm);
+    }
+
+    void set_wakeup_time(const DateTime& d)
+    {
+        g_debug("%s %s", G_STRLOC, G_STRFUNC);
+        std::lock_guard<std::recursive_mutex> lg(m_mutex);
+
+        const auto wakeup_time = d.to_unix();
+
+        // simple sanity check: don't try to wait for something that's already passed
+        const auto now = m_clock->localtime().to_unix();
+        g_return_if_fail (wakeup_time >= now);
+
+        struct timespec sleep_interval;
+        sleep_interval.tv_sec = wakeup_time;
+        sleep_interval.tv_nsec = 0;
+        g_debug("%s %s setting hardware wakeup time to %s (%zu seconds from now)",
+                G_STRLOC, G_STRFUNC,
+                d.format("%F %T").c_str(),
+                (size_t)(wakeup_time - now));
+        u_hardware_alarm_set_relative_to_with_behavior(m_hardware_alarm,
+                                                       U_HARDWARE_ALARM_TIME_REFERENCE_RTC,
+                                                       U_HARDWARE_ALARM_SLEEP_BEHAVIOR_WAKEUP_DEVICE,
+                                                       &sleep_interval);
+    }
+
+    core::Signal<>& timeout() { return m_timeout; }
+
+private:
+
+    void set_wakeup_time_to_the_distant_future()
+    {
+        const auto tomorrow = m_clock->localtime().add_full(0,0,1,0,0,0);
+        set_wakeup_time(tomorrow);
+    }
+
+    static gboolean kick_idle (gpointer gself)
+    {
+        static_cast<Impl*>(gself)->m_timeout();
+
+        return G_SOURCE_REMOVE;
+    }
+
+    void threadfunc()
+    {
+        while (!m_yielding)
+        {
+            // wait for the next hw alarm
+            UHardwareAlarmWaitResult wait_result;
+            g_debug ("calling wait_for_next_alarm");
+            auto rc = u_hardware_alarm_wait_for_next_alarm(m_hardware_alarm, &wait_result);
+            g_return_if_fail (rc == U_STATUS_SUCCESS);
+
+            // set a long wakeup interval for the next iteration of the loop.
+            // if there's another Appointment queued up by the Planner,
+            // our timeout() listener will call set_wakeup_time() to set the
+            // real wakeup interval.
+            set_wakeup_time_to_the_distant_future();
+
+            // delegate the kick back to the main thread
+            g_idle_add (kick_idle, this);
+        }
+    }
+
+    core::Signal<> m_timeout;
+    std::recursive_mutex m_mutex;
+    bool m_yielding = false;
+    const std::shared_ptr<Clock>& m_clock;
+    UHardwareAlarm m_hardware_alarm = nullptr;
+    std::thread m_thread;
+};
+
+/***
+****
+***/
+
+UhaWakeupTimer::UhaWakeupTimer(const std::shared_ptr<Clock>& clock):
+    p(new Impl(clock))
+{
+}
+
+UhaWakeupTimer::~UhaWakeupTimer()
+{
+}
+
+bool UhaWakeupTimer::is_supported()
+{
+    auto hw_alarm = u_hardware_alarm_create();
+    g_debug ("%s hardware alarm %p", G_STRFUNC, hw_alarm);
+    return hw_alarm != nullptr;
+}
+
+void UhaWakeupTimer::set_wakeup_time(const DateTime& d)
+{
+    p->set_wakeup_time(d);
+}
+
+core::Signal<>& UhaWakeupTimer::timeout()
+{
+    return p->timeout();
+}
+
+/***
+****
+***/
+
+} // namespace datetime
+} // namespace indicator
+} // namespace unity