Fix selection timestamp handling problems

* data_device.c (XLClearForeignSelection):
* primary_selection.c (XLClearForeignPrimary): Clear the local
selection as well upon losing selection ownership.
* xdata.c (NoticeClipboardCleared, NoticePrimaryCleared): If a
local selection is in use, don't clear it upon selection clear
events with a timestamp identical to the time at which their
ownership was acquired.  Explain why in a comment.
(HandleSelectionNotify): Always use the client time.

data_device.c

@@ -1210,7 +1210,15 @@ XLClearForeignSelection (Timestamp time)
   if (current_selection_data == &foreign_selection_key)
     {
       current_selection_data = NULL;
-
+      SendDataOffers ();
+    }
+  else if (current_selection_data)
+    {
+      /* The foreign selection was cleared, meaning CLIPBOARD has been
+	 disowned after the last foreign or local selection was set,
+	 and thus the local selection must be cleared as well.  */
+      wl_data_source_send_cancelled (current_selection_data->resource);
+      current_selection_data = NULL;
       SendDataOffers ();
     }
 

primary_selection.c

@@ -756,6 +756,8 @@ XLSetForeignPrimary (Timestamp time, CreateOfferFuncs functions)
 void
 XLClearForeignPrimary (Timestamp time)
 {
+  struct wl_resource *scratch;
+
   if (TimestampIs (time, Earlier, foreign_selection_time))
     return;
 
@@ -764,6 +766,19 @@ XLClearForeignPrimary (Timestamp time)
       primary_selection = NULL;
       NoticeChanged ();
     }
+  else if (primary_selection)
+    {
+      /* The foreign selection was cleared; that means PRIMARY has
+	 been disowned after the last foreign or local selection was
+	 set, which means the local selection must be cleared as
+	 well.  */
+      scratch = primary_selection->resource;
+      zwp_primary_selection_source_v1_send_cancelled (scratch);
+
+      /* Clear the primary selection and notice a change.  */
+      primary_selection = NULL;
+      NoticeChanged ();
+    }
 
   foreign_selection_time = time;
 }

xdata.c

@@ -1093,13 +1093,32 @@ NoticePrimaryChanged (Time time)
 static void
 NoticeClipboardCleared (Time time)
 {
-  /* Ignore outdated events.  */
-  if (TimeIs (time, Earlier, last_x_selection_change))
+  /* Ignore outdated events.  time cannot simply be compared against
+     the selection change time, because some clients do this:
+
+       - data_device.set_selection (data_source, N)
+       - data_source.delete (data_source)
+       - data_device.set_selection (data_source, N)
+
+     Which results in the selection being disowned at the same time as
+     the last selection change time, but then re-owned immediately
+     afterwards, leading to an out-of-date SelectionNotify event with
+     owner None having a timestamp equal to that time.
+
+     Thus, only timestamps after last_x_selection_change are
+     considered as valid here if x_selection_targets is NULL.  */
+
+  if (!x_selection_targets)
+    {
+      if (!TimeIs (time, Later, last_x_selection_change))
+	return;
+    }
+  else if (TimeIs (time, Earlier, last_x_selection_change))
     return;
 
   DebugPrint ("CLIPBOARD was cleared at %lu\n", time);
 
-  last_x_selection_change = TimestampFromServerTime (time);
+  last_x_selection_change = TimestampFromClientTime (time);
   XLClearForeignSelection (last_x_selection_change);
 
   /* Free data that is no longer used.  */
@@ -1111,13 +1130,17 @@ NoticeClipboardCleared (Time time)
 static void
 NoticePrimaryCleared (Time time)
 {
-  /* Ignore outdated events.  */
-  if (TimeIs (time, Earlier, last_primary_time))
+  if (!x_primary_targets)
+    {
+      if (!TimeIs (time, Later, last_primary_time))
+	return;
+    }
+  else if (TimeIs (time, Earlier, last_primary_time))
     return;
 
   DebugPrint ("PRIMARY was cleared at %lu\n", time);
 
-  last_primary_time = TimestampFromServerTime (time);
+  last_primary_time = TimestampFromClientTime (time);
   XLClearForeignPrimary (last_primary_time);
 
   /* Free data that is no longer used.  */
@@ -1133,17 +1156,21 @@ HandleSelectionNotify (XFixesSelectionNotifyEvent *event)
     /* Ignore events sent when we get selection ownership.  */
     return;
 
+  /* Use the server timestamp in the fixes selection notify event
+     to synchronize the local time counter.  */
+  TimestampFromServerTime (event->timestamp);
+
   if (event->selection == CLIPBOARD
       && TimeIs (event->selection_timestamp, Later, last_clipboard_change))
     /* This time is used to keep track of whether or not things like
        disowning the selection were successful.  */
     last_clipboard_change
-      = TimestampFromServerTime (event->selection_timestamp);
+      = TimestampFromClientTime (event->selection_timestamp);
 
   if (event->selection == XA_PRIMARY
       && TimeIs (event->selection_timestamp, Later, last_primary_time))
     last_primary_time
-      = TimestampFromServerTime (event->selection_timestamp);
+      = TimestampFromClientTime (event->selection_timestamp);
 
   if (event->owner != None
       && event->selection == CLIPBOARD)