[california] Allow user adjust start/end date/times either direction: Bug #734408

[Jim Nelson <jnelson src gnome org>]

commit e48ac45ffbfeacce85975dd28f5b772cc5253c75
Author: Jim Nelson <jim yorba org>
Date:   Tue Aug 12 17:23:34 2014 -0700

    Allow user adjust start/end date/times either direction: Bug #734408
    
    This allows for the start/end date/time widget to be freely adjusted
    on either end of the range.  If the user attempts to set an invalid
    value (start time after end time), the other widget will automatically
    adjust attempting to preserve the current duration of time.

 src/host/host-date-time-widget.vala    |    4 ++
 src/host/host-event-time-settings.vala |   54 ++++++++++++++++++++++++-------
 2 files changed, 46 insertions(+), 12 deletions(-)
---
diff --git a/src/host/host-date-time-widget.vala b/src/host/host-date-time-widget.vala
index 081d161..42942d2 100644
--- a/src/host/host-date-time-widget.vala
+++ b/src/host/host-date-time-widget.vala
@@ -147,6 +147,10 @@ public class DateTimeWidget : Gtk.Box {
         return true;
     }
     
+    public Calendar.ExactTime get_exact_time(Calendar.Timezone timezone) {
+        return new Calendar.ExactTime(timezone, date, wall_time);
+    }
+    
     private void connect_property_signals() {
         notify[PROP_DATE].connect(on_date_changed);
         notify[PROP_WALL_TIME].connect(on_wall_time_changed);
diff --git a/src/host/host-event-time-settings.vala b/src/host/host-event-time-settings.vala
index 9440ce2..0b58e84 100644
--- a/src/host/host-event-time-settings.vala
+++ b/src/host/host-event-time-settings.vala
@@ -74,6 +74,7 @@ public class EventTimeSettings : Gtk.Box, Toolkit.Card {
     private Message? message = null;
     private DateTimeWidget from_widget = new DateTimeWidget();
     private DateTimeWidget to_widget = new DateTimeWidget();
+    private Calendar.Duration duration = new Calendar.Duration();
     
     public EventTimeSettings() {
         // need to manually pack the date/time widgets
@@ -112,6 +113,8 @@ public class EventTimeSettings : Gtk.Box, Toolkit.Card {
     public void jumped_to(Toolkit.Card? from, Toolkit.Card.Jump reason, Value? message_value) {
         message = (Message) message_value;
         
+        freeze_widget_notifications();
+        
         Calendar.DateSpan date_span = message.get_event_date_span(Calendar.Timezone.local);
         from_widget.date = date_span.start_date;
         to_widget.date = date_span.end_date;
@@ -122,6 +125,8 @@ public class EventTimeSettings : Gtk.Box, Toolkit.Card {
             Calendar.ExactTimeSpan time_span = message.exact_time_span.to_timezone(Calendar.Timezone.local);
             from_widget.wall_time = time_span.start_exact_time.to_wall_time();
             to_widget.wall_time = time_span.end_exact_time.to_wall_time();
+            
+            duration = time_span.duration;
         } else {
             // set to defaults in case user wants to change from all-day to timed event
             from_widget.wall_time = Calendar.System.now.to_wall_time().round(15, Calendar.TimeUnit.MINUTE,
@@ -133,9 +138,13 @@ public class EventTimeSettings : Gtk.Box, Toolkit.Card {
                 // different days, same time on each day
                 to_widget.wall_time = from_widget.wall_time;
             }
+            
+            duration = date_span.duration;
         }
         
         all_day_checkbutton.active = (message.exact_time_span == null);
+        
+        thaw_widget_notifications();
     }
     
     [GtkCallback]
@@ -153,6 +162,16 @@ public class EventTimeSettings : Gtk.Box, Toolkit.Card {
         jump_to_card_by_name(CreateUpdateEvent.ID, message);
     }
     
+    private void freeze_widget_notifications() {
+        from_widget.freeze_notify();
+        to_widget.freeze_notify();
+    }
+    
+    private void thaw_widget_notifications() {
+        from_widget.thaw_notify();
+        to_widget.thaw_notify();
+    }
+    
     // This does not respect the all-day checkbox
     private Calendar.DateSpan get_date_span() {
         return new Calendar.DateSpan(from_widget.date, to_widget.date);
@@ -160,10 +179,8 @@ public class EventTimeSettings : Gtk.Box, Toolkit.Card {
     
     // This does not respect the all-day checkbox
     private Calendar.ExactTimeSpan get_exact_time_span() {
-        return new Calendar.ExactTimeSpan(
-            new Calendar.ExactTime(Calendar.System.timezone, from_widget.date, from_widget.wall_time),
-            new Calendar.ExactTime(Calendar.System.timezone, to_widget.date, to_widget.wall_time)
-        );
+        return new Calendar.ExactTimeSpan(from_widget.get_exact_time(Calendar.Timezone.local),
+            to_widget.get_exact_time(Calendar.Timezone.local));
     }
     
     private void on_update_summary() {
@@ -177,17 +194,30 @@ public class EventTimeSettings : Gtk.Box, Toolkit.Card {
     }
     
     private void on_from_changed() {
-        // clamp to_widget to not allow earlier date/times than from_widget
-        to_widget.floor = new Calendar.ExactTime(Calendar.System.timezone, from_widget.date,
-            from_widget.wall_time);
-        
-        on_update_summary();
+        on_date_time_changed(from_widget, to_widget, (int) duration.seconds);
     }
     
     private void on_to_changed() {
-        // clamp from_widget to not allow later date/times than to_widget
-        from_widget.ceiling = new Calendar.ExactTime(Calendar.System.timezone, to_widget.date,
-            to_widget.wall_time);
+        on_date_time_changed(to_widget, from_widget, 0 - (int) duration.seconds);
+    }
+    
+    private void on_date_time_changed(DateTimeWidget source, DateTimeWidget other, int duration_adjustment) {
+        // if From is pushed forward beyond To (or To pushed back before From), adjust the other
+        // widget to maintain the user's duration
+        Calendar.ExactTime from_exact_time = from_widget.get_exact_time(Calendar.Timezone.local);
+        Calendar.ExactTime to_exact_time = to_widget.get_exact_time(Calendar.Timezone.local);
+        if (from_exact_time.compare_to(to_exact_time) >= 0) {
+            Calendar.ExactTime adjusted = source.get_exact_time(Calendar.Timezone.local)
+                .adjust_time(duration_adjustment, Calendar.TimeUnit.SECOND);
+            
+            freeze_widget_notifications();
+            other.date = new Calendar.Date.from_exact_time(adjusted);
+            other.wall_time = adjusted.to_wall_time();
+            thaw_widget_notifications();
+        } else {
+            // otherwise, this is the new duration to be maintained
+            duration = new Calendar.Duration(0, 0, 0, to_exact_time.difference(from_exact_time));
+        }
         
         on_update_summary();
     }