[evolution] [itip-formatter] Guess meeting time zone when not provided in the invitation

[Milan Crha <mcrha src gnome org>]

commit 761ac9f0045eb2c24f509f4a5a712502bfac29d7
Author: Milan Crha <mcrha redhat com>
Date:   Wed Aug 31 15:27:31 2016 +0200

    [itip-formatter] Guess meeting time zone when not provided in the invitation
    
    In case the meeting invitation component doesn't contain its timezone(s),
    try to guess it from the given TZID, thus the time shown in the message
    preview is properly converted into the local time zone.

 modules/itip-formatter/itip-view.c |   37 ++++++++++++++++++++++++++++++++---
 1 files changed, 33 insertions(+), 4 deletions(-)
---
diff --git a/modules/itip-formatter/itip-view.c b/modules/itip-formatter/itip-view.c
index 8f55d28..4ffde23 100644
--- a/modules/itip-formatter/itip-view.c
+++ b/modules/itip-formatter/itip-view.c
@@ -5720,6 +5720,29 @@ in_proper_folder (CamelFolder *folder)
        return res;
 }
 
+static icaltimezone *
+itip_view_guess_timezone (const gchar *tzid)
+{
+       icaltimezone *zone;
+
+       if (!tzid || !*tzid)
+               return NULL;
+
+       zone = icaltimezone_get_builtin_timezone (tzid);
+       if (zone)
+               return zone;
+
+       zone = icaltimezone_get_builtin_timezone_from_tzid (tzid);
+       if (zone)
+               return zone;
+
+       tzid = e_cal_match_tzid (tzid);
+       if (tzid)
+               zone = icaltimezone_get_builtin_timezone_from_tzid (tzid);
+
+       return zone;
+}
+
 void
 itip_view_init_view (ItipView *view)
 {
@@ -5979,9 +6002,12 @@ itip_view_init_view (ItipView *view)
                 /* Should we guess if the timezone is an olsen name somehow? */
                if (datetime.value->is_utc)
                        from_zone = icaltimezone_get_utc_timezone ();
-               else if (!datetime.value->is_utc && datetime.tzid)
+               else if (!datetime.value->is_utc && datetime.tzid) {
                        from_zone = icalcomponent_get_timezone (view->priv->top_level, datetime.tzid);
-               else
+
+                       if (!from_zone)
+                               from_zone = itip_view_guess_timezone (datetime.tzid);
+               } else
                        from_zone = NULL;
 
                start_tm = icaltimetype_to_tm_with_zone (datetime.value, from_zone, to_zone);
@@ -6015,9 +6041,12 @@ itip_view_init_view (ItipView *view)
                 /* Should we guess if the timezone is an olsen name somehow? */
                if (datetime.value->is_utc)
                        from_zone = icaltimezone_get_utc_timezone ();
-               else if (!datetime.value->is_utc && datetime.tzid)
+               else if (!datetime.value->is_utc && datetime.tzid) {
                        from_zone = icalcomponent_get_timezone (view->priv->top_level, datetime.tzid);
-               else
+
+                       if (!from_zone)
+                               from_zone = itip_view_guess_timezone (datetime.tzid);
+               } else
                        from_zone = NULL;
 
                if (datetime.value->is_date) {