[gnome-settings-daemon] color: Add GDateTimeSource from the gnome-desktop module

[Richard Hughes <rhughes src gnome org>]

commit 0b6028944936921227ebe6389b5fc5202299d29f
Author: Richard Hughes <richard hughsie com>
Date:   Thu Feb 2 14:41:02 2017 +0000

    color: Add GDateTimeSource from the gnome-desktop module
    
    We'll need this for in the color plugin so we can poll according to the
    wall-clock time, rather than the monotonic time. This ensures we do the right
    thing when the time is changed backwards or forwards.
    
    See https://bugzilla.gnome.org/show_bug.cgi?id=778039 for more details.

 plugins/color/Makefile.am             |    2 +
 plugins/color/gnome-datetime-source.c |  286 +++++++++++++++++++++++++++++++++
 plugins/color/gnome-datetime-source.h |   38 +++++
 3 files changed, 326 insertions(+), 0 deletions(-)
---
diff --git a/plugins/color/Makefile.am b/plugins/color/Makefile.am
index 8ec20e1..a8e9567 100644
--- a/plugins/color/Makefile.am
+++ b/plugins/color/Makefile.am
@@ -29,6 +29,8 @@ TESTS = gcm-self-test
 libexec_PROGRAMS = gsd-color
 gsd_color_SOURCES =                    \
        main.c                          \
+       gnome-datetime-source.c         \
+       gnome-datetime-source.h         \
        gcm-edid.c                      \
        gcm-edid.h                      \
        gsd-color-calibrate.c           \
diff --git a/plugins/color/gnome-datetime-source.c b/plugins/color/gnome-datetime-source.c
new file mode 100644
index 0000000..633d7ee
--- /dev/null
+++ b/plugins/color/gnome-datetime-source.c
@@ -0,0 +1,286 @@
+/* -*- mode: C; c-file-style: "linux"; indent-tabs-mode: t -*-
+ * gdatetime-source.c - copy&paste from https://bugzilla.gnome.org/show_bug.cgi?id=655129
+ *
+ * Copyright (C) 2011 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public License
+ * as published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * Author: Colin Walters <walters verbum org>
+ */
+
+#include "config.h"
+
+#define GNOME_DESKTOP_USE_UNSTABLE_API
+#include "gnome-datetime-source.h"
+
+#ifdef HAVE_TIMERFD
+#include <sys/timerfd.h>
+#include <unistd.h>
+#include <string.h>
+#endif
+
+typedef struct _GDateTimeSource GDateTimeSource;
+struct _GDateTimeSource
+{
+       GSource     source;
+  
+       gint64      real_expiration;
+       gint64      wakeup_expiration;
+
+       gboolean    cancel_on_set : 1;
+       gboolean    initially_expired : 1;
+
+       GPollFD     pollfd;
+};
+
+static inline void
+g_datetime_source_reschedule (GDateTimeSource *datetime_source,
+                             gint64                from_monotonic)
+{
+       datetime_source->wakeup_expiration = from_monotonic + G_TIME_SPAN_SECOND;
+}
+
+static gboolean
+g_datetime_source_is_expired (GDateTimeSource *datetime_source)
+{
+       gint64 real_now;
+       gint64 monotonic_now;
+
+       real_now = g_get_real_time ();
+       monotonic_now = g_source_get_time ((GSource*)datetime_source);
+
+       if (datetime_source->initially_expired)
+               return TRUE;
+  
+       if (datetime_source->real_expiration <= real_now)
+               return TRUE;
+
+       /* We can't really detect without system support when things
+        * change; so just trigger every second (i.e. our wakeup
+        * expiration)
+        */
+       if (datetime_source->cancel_on_set && monotonic_now >= datetime_source->wakeup_expiration)
+               return TRUE;
+
+       return FALSE;
+}
+
+/* In prepare, we're just checking the monotonic time against
+ * our projected wakeup.
+ */
+static gboolean
+g_datetime_source_prepare (GSource *source,
+                          gint    *timeout)
+{
+       GDateTimeSource *datetime_source = (GDateTimeSource*)source;
+       gint64 monotonic_now;
+
+#ifdef HAVE_TIMERFD
+       if (datetime_source->pollfd.fd != -1) {
+               *timeout = -1;
+               return datetime_source->initially_expired;  /* Should be TRUE at most one time, FALSE forever 
after */
+       }
+#endif
+
+       monotonic_now = g_source_get_time (source);
+
+       if (monotonic_now < datetime_source->wakeup_expiration) {
+               /* Round up to ensure that we don't try again too early */
+               *timeout = (datetime_source->wakeup_expiration - monotonic_now + 999) / 1000;
+               return FALSE;
+       }
+
+       *timeout = 0;
+       return g_datetime_source_is_expired (datetime_source);
+}
+
+/* In check, we're looking at the wall clock.
+ */
+static gboolean 
+g_datetime_source_check (GSource  *source)
+{
+       GDateTimeSource *datetime_source = (GDateTimeSource*)source;
+
+#ifdef HAVE_TIMERFD
+       if (datetime_source->pollfd.fd != -1)
+               return datetime_source->pollfd.revents != 0;
+#endif
+
+       if (g_datetime_source_is_expired (datetime_source))
+               return TRUE;
+
+       g_datetime_source_reschedule (datetime_source, g_source_get_time (source));
+  
+       return FALSE;
+}
+
+static gboolean
+g_datetime_source_dispatch (GSource    *source, 
+                           GSourceFunc callback,
+                           gpointer    user_data)
+{
+       GDateTimeSource *datetime_source = (GDateTimeSource*)source;
+
+       datetime_source->initially_expired = FALSE;
+
+       if (!callback) {
+               g_warning ("Timeout source dispatched without callback\n"
+                          "You must call g_source_set_callback().");
+               return FALSE;
+       }
+  
+       (callback) (user_data);
+
+       /* Always false as this source is documented to run once */
+       return FALSE;
+}
+
+static void
+g_datetime_source_finalize (GSource *source)
+{
+#ifdef HAVE_TIMERFD
+       GDateTimeSource *datetime_source = (GDateTimeSource*)source;
+       if (datetime_source->pollfd.fd != -1)
+               close (datetime_source->pollfd.fd);
+#endif
+}
+
+static GSourceFuncs g_datetime_source_funcs = {
+       g_datetime_source_prepare,
+       g_datetime_source_check,
+       g_datetime_source_dispatch,
+       g_datetime_source_finalize
+};
+
+#ifdef HAVE_TIMERFD
+static gboolean
+g_datetime_source_init_timerfd (GDateTimeSource *datetime_source,
+                               gint64           expected_now_seconds,
+                               gint64           unix_seconds)
+{
+       struct itimerspec its;
+       int settime_flags;
+
+       datetime_source->pollfd.fd = timerfd_create (CLOCK_REALTIME, TFD_CLOEXEC);
+       if (datetime_source->pollfd.fd == -1)
+               return FALSE;
+
+       memset (&its, 0, sizeof (its));
+       its.it_value.tv_sec = (time_t) unix_seconds;
+
+       /* http://article.gmane.org/gmane.linux.kernel/1132138 */
+#ifndef TFD_TIMER_CANCEL_ON_SET
+#define TFD_TIMER_CANCEL_ON_SET (1 << 1)
+#endif
+
+       settime_flags = TFD_TIMER_ABSTIME;
+       if (datetime_source->cancel_on_set)
+               settime_flags |= TFD_TIMER_CANCEL_ON_SET;
+
+       if (timerfd_settime (datetime_source->pollfd.fd, settime_flags, &its, NULL) < 0) {
+               close (datetime_source->pollfd.fd);
+               datetime_source->pollfd.fd = -1;
+               return FALSE;
+       }
+
+       /* Now we need to check that the clock didn't go backwards before we
+        * had the timerfd set up.  See
+        * https://bugzilla.gnome.org/show_bug.cgi?id=655129
+        */
+       clock_gettime (CLOCK_REALTIME, &its.it_value);
+       if (its.it_value.tv_sec < expected_now_seconds)
+               datetime_source->initially_expired = TRUE;
+
+       datetime_source->pollfd.events = G_IO_IN;
+
+       g_source_add_poll ((GSource*) datetime_source, &datetime_source->pollfd);
+
+       return TRUE;
+}
+#endif
+
+/**
+ * _gnome_date_time_source_new:
+ * @now: The expected current time
+ * @expiry: Time to await
+ * @cancel_on_set: Also invoke callback if the system clock changes discontiguously
+ *
+ * This function is designed for programs that want to schedule an
+ * event based on real (wall clock) time, as returned by
+ * g_get_real_time().  For example, HOUR:MINUTE wall-clock displays
+ * and calendaring software.  The callback will be invoked when the
+ * specified wall clock time @expiry is reached.  This includes
+ * events such as the system clock being set past the given time.
+ *
+ * Compare versus g_timeout_source_new() which is defined to use
+ * monotonic time as returned by g_get_monotonic_time().
+ *
+ * The parameter @now is necessary to avoid a race condition in
+ * between getting the current time and calling this function.
+ *
+ * If @cancel_on_set is given, the callback will also be invoked at
+ * most a second after the system clock is changed.  This includes
+ * being set backwards or forwards, and system
+ * resume from suspend.  Not all operating systems allow detecting all
+ * relevant events efficiently - this function may cause the process
+ * to wake up once a second in those cases.
+ *
+ * A wall clock display should use @cancel_on_set; a calendaring
+ * program shouldn't need to.
+ *
+ * Note that the return value from the associated callback will be
+ * ignored; this is a one time watch.
+ *
+ * <note><para>This function currently does not detect time zone
+ * changes.  On Linux, your program should also monitor the
+ * <literal>/etc/timezone</literal> file using
+ * #GFileMonitor.</para></note>
+ *
+ * <example id="gdatetime-example-watch"><title>Clock example</title><programlisting><xi:include 
xmlns:xi="http://www.w3.org/2001/XInclude"; parse="text" 
href="../../../../glib/tests/glib-clock.c"><xi:fallback>FIXME: MISSING XINCLUDE 
CONTENT</xi:fallback></xi:include></programlisting></example>
+ *
+ * Return value: A newly-constructed #GSource
+ *
+ * Since: 2.30
+ **/
+GSource *
+_gnome_datetime_source_new (GDateTime  *now,
+                           GDateTime  *expiry,
+                           gboolean    cancel_on_set)
+{
+       GDateTimeSource *datetime_source;
+       gint64 unix_seconds;
+
+       unix_seconds = g_date_time_to_unix (expiry);
+
+       datetime_source = (GDateTimeSource*) g_source_new (&g_datetime_source_funcs, sizeof 
(GDateTimeSource));
+
+       datetime_source->cancel_on_set = cancel_on_set;
+
+#ifdef HAVE_TIMERFD
+       {
+               gint64 expected_now_seconds = g_date_time_to_unix (now);
+               if (g_datetime_source_init_timerfd (datetime_source, expected_now_seconds, unix_seconds))
+                       return (GSource*)datetime_source;
+               /* Fall through to non-timerfd code */
+       }
+#endif
+
+       datetime_source->real_expiration = unix_seconds * 1000000;
+       g_datetime_source_reschedule (datetime_source, g_get_monotonic_time ());
+
+       return (GSource*)datetime_source;
+}
+
diff --git a/plugins/color/gnome-datetime-source.h b/plugins/color/gnome-datetime-source.h
new file mode 100644
index 0000000..e9ecbf0
--- /dev/null
+++ b/plugins/color/gnome-datetime-source.h
@@ -0,0 +1,38 @@
+/* gnome-rr.h
+ *
+ * Copyright 2011, Red Hat, Inc.
+ * 
+ * This file is part of the Gnome Library.
+ * 
+ * The Gnome Library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * The Gnome Library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with the Gnome Library; see the file COPYING.LIB.  If not,
+ * write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ * 
+ * Author: Colin Walters <walters verbum org>
+ */
+
+#ifndef GNOME_DATETIME_SOURCE_H
+#define GNOME_DATETIME_SOURCE_H
+
+#ifndef GNOME_DESKTOP_USE_UNSTABLE_API
+#error    This is unstable API. You must define GNOME_DESKTOP_USE_UNSTABLE_API
+#endif
+
+#include <glib.h>
+
+GSource *_gnome_datetime_source_new (GDateTime *now,
+                                    GDateTime *expiry,
+                                    gboolean   cancel_on_set);
+
+#endif /* GNOME_DATETIME_SOURCE_H */