Improve reliability of timestamp handling

* 12to11.c (DetermineServerTime): Correctly handle server time
truncation.
* Imakefile (SRCS): Add time.c
(OBJS): Add time.o.
* compositor.h (struct _Timestamp, enum _TimestampDifference):
New structure and enum.
(TimestampIs, TimeIs): New macros.
(struct _CreateOfferFuncs): Accept Timestamp, not Time.
* data_device.c (UpdateSingleReferenceWithForeignOffer)
(XLSetForeignSelection, XLClearForeignSelection): Accept
Timestamp, not Time.
* dnd.c (XLDoDragMotion):
* picture_renderer.c (InitRenderFuncs):
* primary_selection.c (UpdateSingleReferenceWithForeignOffer)
(XLSetForeignPrimary, XLClearForeignPrimary): Adjust for changed
timestamp handling.
* seat.c (struct _Seat): New field `last_user_time'.
(HandleRawKey, DispatchMotion): Record last user time as
timestamp.
(GetLastUserTime, XLSeatGetLastUserTime): Return Timestamp, not
Time.
* select.c (FindWriteTransfer, TransferFinished)
(TransferBecameReadable, ConvertSelectionMultiple)
(HandleSelectionRequest, DrainQueuedTransfers)
(HandlePropertyDelete, HandlePropertyNotify): Allow duplicate
write transfers if the other is only waiting for property
deletion.
* xdata.c (ReceiveBody, HandleOfferResourceDestroy)
(AllocateTimestamp, CreateOffer, CreatePrimaryOffer, SendOffers)
(SendPrimaryOffers, HandleNewSelection, NoticeClipboardCleared)
(NoticePrimaryCleared, HandleSelectionNotify)
(XLNoteSourceDestroyed, NoteLocalSelectionBody)
(NoteLocalSelectionFooter): Adjust timestamp handling to use
wraparound-safe Timestamp and not Time.

12to11.c

@@ -34,7 +34,8 @@ static void
 DetermineServerTime (void)
 {
   Time server_time;
-  struct timespec clock_spec, server_spec, diff;
+  struct timespec clock_spec;
+  uint64_t clock_ms, truncated;
 
   /* Try to determine if the X server time is the same as the
      monotonic time.  If it is not, certain features such as "active"
@@ -42,20 +43,28 @@ DetermineServerTime (void)
 
   clock_gettime (CLOCK_MONOTONIC, &clock_spec);
   server_time = XLGetServerTimeRoundtrip ();
-  server_spec.tv_sec = server_time / 1000;
-  server_spec.tv_nsec = ((server_time - server_time / 1000 * 1000)
-			 * 1000000);
 
-  diff = TimespecSub (server_spec, clock_spec);
+  /* Convert the monotonic time to milliseconds.  */
 
-  if (TimespecCmp (diff, MakeTimespec (0, 50000000)) <= 0
+  if (IntMultiplyWrapv (clock_spec.tv_sec, 1000, &clock_ms))
-      || TimespecCmp (diff, MakeTimespec (0, -50000000)) <= 0)
+    goto overflow;
+
+  if (IntAddWrapv (clock_ms, clock_spec.tv_nsec / 1000000,
+		   &clock_ms))
+    goto overflow;
+
+  /* Truncate the time to 32 bits.  */
+  truncated = clock_ms;
+
+  /* Compare the clock time with the server time.  */
+  if (llabs ((long long) server_time - (long long) truncated) <= 5)
     /* Since the difference between the server time and the monotonic
-       time is less than 50 ms, the server time is the monotonic
+       time is less than 5 ms, the server time is most likely the
-       time.  */
+       monotonic time.  */
     compositor.server_time_monotonic = True;
   else
     {
+    overflow:
       compositor.server_time_monotonic = False;
       fprintf (stderr, "Warning: the X server time does not seem to"
 	       " be synchronized with the monotonic time.  Multiple"

Imakefile

@@ -23,7 +23,8 @@ SRCS = 12to11.c run.c alloc.c fns.c output.c compositor.c       \
   icon_surface.c primary_selection.c renderer.c                 \
   picture_renderer.c explicit_synchronization.c transform.c     \
   wp_viewporter.c decoration.c text_input.c                     \
-  single_pixel_buffer.c drm_lease.c pointer_constraints.c
+  single_pixel_buffer.c drm_lease.c pointer_constraints.c       \
+  time.c
 
 OBJS = 12to11.o run.o alloc.o fns.o output.o compositor.o       \
   surface.o region.o shm.o atoms.o subcompositor.o positioner.o \
@@ -33,7 +34,8 @@ OBJS = 12to11.o run.o alloc.o fns.o output.o compositor.o       \
   icon_surface.o primary_selection.o renderer.o                 \
   picture_renderer.o explicit_synchronization.o transform.o     \
   wp_viewporter.o decoration.o text_input.o                     \
-  single_pixel_buffer.o drm_lease.o pointer_constraints.o
+  single_pixel_buffer.o drm_lease.o pointer_constraints.o       \
+  time.o
 
 GENHEADERS = transfer_atoms.h
 

compositor.h

@@ -103,6 +103,35 @@ typedef struct _ViewportExt ViewportExt;
 
 extern Compositor compositor;
 
+/* Defined in time.c.  */
+
+typedef struct _Timestamp Timestamp;
+typedef enum _TimestampDifference TimestampDifference;
+
+struct _Timestamp
+{
+  /* Number of server months passed.  */
+  unsigned int months;
+
+  /* Millisecond time into those months.  */
+  unsigned int milliseconds;
+};
+
+enum _TimestampDifference
+  {
+    Earlier,
+    Same,
+    Later,
+  };
+
+extern Timestamp TimestampFromServerTime (Time);
+extern Timestamp TimestampFromClientTime (Time);
+extern TimestampDifference CompareTimestamps (Timestamp, Timestamp);
+extern TimestampDifference CompareTimeWith (Time, Timestamp);
+
+#define TimestampIs(a, op, b)	(CompareTimestamps ((a), (b)) == (op))
+#define TimeIs(a, op, b)	(CompareTimeWith ((a), (b)) == (op))
+
 /* Defined in renderer.c.  */
 
 typedef struct _RenderFuncs RenderFuncs;
@@ -1301,12 +1330,16 @@ typedef struct _DataSource DataSource;
 typedef struct _CreateOfferFuncs CreateOfferFuncs;
 typedef struct _DndOfferFuncs DndOfferFuncs;
 
-typedef struct wl_resource *(*CreateOfferFunc) (struct wl_client *, Time);
+typedef struct wl_resource *(*CreateOfferFunc) (struct wl_client *,
-typedef void (*SendDataFunc) (struct wl_resource *, Time);
+						Timestamp);
+typedef void (*SendDataFunc) (struct wl_resource *, Timestamp);
 
 struct _CreateOfferFuncs
 {
+  /* Function called to create data offers.  */
   CreateOfferFunc create_offer;
+
+  /* Function called to send data offers.  */
   SendDataFunc send_offers;
 };
 
@@ -1321,8 +1354,8 @@ extern void XLRetainDataDevice (DataDevice *);
 extern void XLReleaseDataDevice (DataDevice *);
 extern void XLDataDeviceClearSeat (DataDevice *);
 extern void XLDataDeviceHandleFocusChange (DataDevice *);
-extern void XLSetForeignSelection (Time, CreateOfferFuncs);
+extern void XLSetForeignSelection (Timestamp, CreateOfferFuncs);
-extern void XLClearForeignSelection (Time);
+extern void XLClearForeignSelection (Timestamp);
 extern int XLDataSourceTargetCount (DataSource *);
 extern void XLDataSourceGetTargets (DataSource *, Atom *);
 extern struct wl_resource *XLResourceFromDataSource (DataSource *);
@@ -1391,7 +1424,7 @@ extern Bool XLSeatIsInert (Seat *);
 extern Bool XLSeatIsClientFocused (Seat *, struct wl_client *);
 extern Surface *XLSeatGetFocus (Seat *);
 extern void XLSeatShowWindowMenu (Seat *, Surface *, int, int);
-extern Time XLSeatGetLastUserTime (Seat *);
+extern Timestamp XLSeatGetLastUserTime (Seat *);
 extern void XLSeatBeginDrag (Seat *, DataSource *, Surface *,
 			     Surface *, uint32_t);
 extern DataSource *XLSeatGetDragDataSource (Seat *);
@@ -1507,8 +1540,8 @@ extern Bool XLIsWindowIconSurface (Window);
 /* Defined in primary_selection.c.  */
 
 extern void XLInitPrimarySelection (void);
-extern void XLSetForeignPrimary (Time, CreateOfferFuncs);
+extern void XLSetForeignPrimary (Timestamp, CreateOfferFuncs);
-extern void XLClearForeignPrimary (Time);
+extern void XLClearForeignPrimary (Timestamp);
 extern Bool XLNoteLocalPrimary (Seat *, PDataSource *);
 extern void XLPrimarySelectionHandleFocusChange (Seat *);
 extern struct wl_resource *XLResourceFromPDataSource (PDataSource *);

data_device.c

@@ -163,7 +163,7 @@ static DataSource foreign_selection_key;
 static CreateOfferFuncs foreign_selection_functions;
 
 /* Time the foreign selection was changed.  */
-static Time foreign_selection_time;
+static Timestamp foreign_selection_time;
 
 /* When it changed.  */
 static uint32_t last_selection_change_serial;
@@ -759,7 +759,7 @@ UpdateSingleReferenceWithForeignOffer (struct wl_client *client,
 				       DataDeviceReference *reference)
 {
   struct wl_resource *resource;
-  Time time;
+  Timestamp time;
 
   time = foreign_selection_time;
   resource = foreign_selection_functions.create_offer (client, time);
@@ -1173,11 +1173,11 @@ XLDataDeviceHandleFocusChange (DataDevice *device)
 }
 
 void
-XLSetForeignSelection (Time time, CreateOfferFuncs functions)
+XLSetForeignSelection (Timestamp time, CreateOfferFuncs functions)
 {
   uint32_t serial;
 
-  if (time < foreign_selection_time)
+  if (TimestampIs (time, Earlier, foreign_selection_time))
     return;
 
   serial = wl_display_next_serial (compositor.wl_display);
@@ -1202,9 +1202,9 @@ XLSetForeignSelection (Time time, CreateOfferFuncs functions)
 }
 
 void
-XLClearForeignSelection (Time time)
+XLClearForeignSelection (Timestamp time)
 {
-  if (time < foreign_selection_time)
+  if (TimestampIs (time, Earlier, foreign_selection_time))
     return;
 
   if (current_selection_data == &foreign_selection_key)

dnd.c

@@ -2920,6 +2920,7 @@ XLDoDragMotion (Seat *seat, double root_x, double root_y)
 {
   Window toplevel, proxy, self;
   int version, proxy_version;
+  Timestamp timestamp;
 
   if (finish_source || drag_state.flags & PendingDrop)
     /* A finish is pending.  */
@@ -2960,7 +2961,8 @@ XLDoDragMotion (Seat *seat, double root_x, double root_y)
   /* Try to own XdndSelection with the last user time.  */
   if (!(drag_state.flags & SelectionSet))
     {
-      drag_state.timestamp = XLSeatGetLastUserTime (seat);
+      timestamp = XLSeatGetLastUserTime (seat);
+      drag_state.timestamp = timestamp.milliseconds;
 
       if (!XLOwnDragSelection (drag_state.timestamp,
 			       XLSeatGetDragDataSource (seat)))

picture_renderer.c

@@ -673,8 +673,8 @@ InitRenderFuncs (void)
       || !XPresentQueryVersion (compositor.display,
 				&major, &minor))
     {
-      fprintf (stderr, "the X presentation extension is not supported"
+      fprintf (stderr, "The X presentation extension is not supported"
-	       " by this X server");
+	       " by this X server\n");
       return False;
     }
 

primary_selection.c

@@ -101,7 +101,7 @@ static PDataSource foreign_selection_key;
 static CreateOfferFuncs foreign_selection_functions;
 
 /* The time the foreign selection was set.  */
-static Time foreign_selection_time;
+static Timestamp foreign_selection_time;
 
 /* Forward declaration.  */
 
@@ -354,7 +354,7 @@ UpdateSingleReferenceWithForeignOffer (struct wl_client *client,
 				       PDataDevice *reference)
 {
   struct wl_resource *scratch, *resource;
-  Time time;
+  Timestamp time;
 
   time = foreign_selection_time;
   resource = foreign_selection_functions.create_offer (client, time);
@@ -721,12 +721,12 @@ HandleBind (struct wl_client *client, void *data, uint32_t version,
 
 
 void
-XLSetForeignPrimary (Time time, CreateOfferFuncs functions)
+XLSetForeignPrimary (Timestamp time, CreateOfferFuncs functions)
 {
   uint32_t serial;
   struct wl_resource *scratch;
 
-  if (time < foreign_selection_time)
+  if (TimestampIs (time, Earlier, foreign_selection_time))
     return;
 
   serial = wl_display_next_serial (compositor.wl_display);
@@ -754,9 +754,9 @@ XLSetForeignPrimary (Time time, CreateOfferFuncs functions)
 }
 
 void
-XLClearForeignPrimary (Time time)
+XLClearForeignPrimary (Timestamp time)
 {
-  if (time < foreign_selection_time)
+  if (TimestampIs (time, Earlier, foreign_selection_time))
     return;
 
   if (primary_selection == &foreign_selection_key)

seat.c

@@ -337,6 +337,9 @@ struct _ModifierChangeCallback
 
 struct _Seat
 {
+  /* The last user time.  */
+  Timestamp last_user_time;
+
   /* wl_global associated with this seat.  */
   struct wl_global *global;
 
@@ -2367,6 +2370,9 @@ HandleRawKey (XIRawEvent *event)
 
   /* This is used for tracking grabs.  */
   seat->its_depress_time = event->time;
+
+  /* Update the last user time.  */
+  seat->last_user_time = TimestampFromServerTime (event->time);
 }
 
 static void
@@ -3730,6 +3736,9 @@ DispatchMotion (Subcompositor *subcompositor, XIDeviceEvent *xev)
   seat->its_root_y = xev->root_y;
   seat->its_press_time = xev->time;
 
+  /* Update the last user time.  */
+  seat->last_user_time = TimestampFromServerTime (xev->time);
+
   actual_dispatch = FindSurfaceUnder (subcompositor, xev->event_x,
 				      xev->event_y);
 
@@ -4375,11 +4384,10 @@ IdentifySeat (WhatEdge *edge, uint32_t serial)
   return NULL;
 }
 
-static Time
+static Timestamp
 GetLastUserTime (Seat *seat)
 {
-  return MAX (seat->its_press_time,
+  return seat->last_user_time;
-	      seat->its_depress_time);
 }
 
 static Bool
@@ -5361,7 +5369,7 @@ XLSeatBeginDrag (Seat *seat, DataSource *data_source, Surface *start_surface,
   seat->flags &= ~IsDropped;
 }
 
-Time
+Timestamp
 XLSeatGetLastUserTime (Seat *seat)
 {
   return GetLastUserTime (seat);

select.c

@@ -757,19 +757,23 @@ GetTransferFunction (SelectionOwnerInfo *info,
 }
 
 static WriteTransfer *
-FindWriteTransfer (Window requestor, Atom property)
+FindWriteTransfer (Window requestor, Atom property,
+		   int ignore_state)
 {
   WriteTransfer *transfer;
 
-  transfer = write_transfers.next;
+  transfer = write_transfers.last;
 
   while (transfer != &write_transfers)
     {
       if (transfer->requestor == requestor
-	  && transfer->property == property)
+	  && transfer->property == property
+	  && (!ignore_state
+	      || ((transfer->state & ignore_state)
+		  != ignore_state)))
 	return transfer;
 
-      transfer = transfer->next;
+      transfer = transfer->last;
     }
 
   return NULL;
@@ -1036,12 +1040,12 @@ TransferFinished (WriteTransfer *transfer)
 	      transfer if nothing has previously been written.  */
 	   || !(transfer->state & IsFlushed))
     {
+      DebugPrint ("Transfer finished, but there is still property data"
+		  " unwritten (offset %td)\n", transfer->offset);
+
       /* There is still property data left to be written.  */
       FlushTransfer (transfer, True);
       transfer->state |= IsFinished;
-
-      DebugPrint ("Transfer finished, but there is still property data"
-		  " unwritten\n");
     }
   else
     /* The transfer is really finished.  */
@@ -1107,8 +1111,9 @@ TransferBecameReadable (WriteTransfer *transfer)
     }
   else
     {
-      DebugPrint ("Transfer complete, bytes read as part of EOF: %td, off: %td\n",
+      DebugPrint ("Transfer complete, bytes read as part of EOF: %td, "
-		  transfer->offset, transfer->size);
+		  "off: %td size: %td\n", bytes_read, transfer->offset,
+		  transfer->size);
 
       transfer->offset += bytes_read;
       TransferFinished (transfer);
@@ -1239,11 +1244,12 @@ ConvertSelectionMultiple (SelectionOwnerInfo *info, XEvent *event,
       DebugPrint ("Verifying MULTIPLE transfer; target = %lu, property = %lu\n",
 		  atoms[i + 0], atoms[i + 1]);
 
-      if (FindWriteTransfer (event->xselectionrequest.requestor, atoms[1])
+      if (FindWriteTransfer (event->xselectionrequest.requestor, atoms[1], 0)
 	  || FindQueuedTransfer (event->xselectionrequest.requestor, atoms[1]))
 	{
 	  DebugPrint ("Found ongoing selection transfer with same requestor "
-		      "and property; this MULTIPLE request will have to be queued.\n");
+		      "and property; this MULTIPLE request will have to be "
+		      "queued.\n");
 
 	  QueueTransfer (event);
 
@@ -1390,7 +1396,7 @@ static Bool
 HandleSelectionRequest (XEvent *event)
 {
   XEvent notify;
-  WriteTransfer *transfer;
+  WriteTransfer *transfer, *existing_transfer;
   long quantum;
   SelectionOwnerInfo *info;
 
@@ -1428,8 +1434,51 @@ HandleSelectionRequest (XEvent *event)
 
   /* If a selection request with the same property and window already
      exists, delay this request for later.  */
-  if (FindWriteTransfer (event->xselectionrequest.requestor,
+  existing_transfer
-			 event->xselectionrequest.property)
+    = FindWriteTransfer (event->xselectionrequest.requestor,
+			 event->xselectionrequest.property,
+			 /* Ignore write transfers that are finished
+			    but pending property deletion.  If the
+			    existing transfer is finished, but we are
+			    still waiting for property deletion, allow
+			    the new transfer to take place.  This is
+			    because some very popular programs ask for
+			    TARGETS, and then ask for STRING with the
+			    same property, but only delete the
+			    property for the first request after the
+			    data for the second request arrives.  This
+			    is against the ICCCM, as it says:
+
+			      The requestor should set the property
+			      argument to the name of a property that
+			      the owner can use to report the value of
+			      the selection.  Requestors should ensure
+			      that the named property does not exist
+			      on the window before issuing the
+			      ConvertSelection request.
+
+			    and:
+
+			      Once all the data in the selection has
+			      been retrieved (which may require
+			      getting the values of several properties
+			      -- see the section called "Use of
+			      Selection Properties". ), the requestor
+			      should delete the property in the
+			      SelectionNotify request by using a
+			      GetProperty request with the delete
+			      argument set to True.  As previously
+			      discussed, the owner has no way of
+			      knowing when the data has been
+			      transferred to the requestor unless the
+			      property is removed.
+
+			    Both paragraphs mean that the property
+			    should have been deleted by the time the
+			    second request is made! */
+			 IsFinished | IsWaitingForDelete);
+
+  if (existing_transfer
       /* We need to look at the queue too; otherwise, events from the
 	 future might be handled out of order, if the original write
 	 transfer is gone, but some events are still queued.  */
@@ -1549,9 +1598,9 @@ DrainQueuedTransfers (void)
 
   /* Then, read from the other side of the queue, and handle
      everything.  */
-  item = queued_transfers.last;
+  item = temp.last;
 
-  while (item != &queued_transfers)
+  while (item != &temp)
     {
       last = item;
       item = item->last;
@@ -1601,29 +1650,36 @@ HandleSelectionNotify (XEvent *event)
 static Bool
 HandlePropertyDelete (XEvent *event)
 {
-  WriteTransfer *transfer;
+  WriteTransfer *transfer, *last;
 
-  transfer = FindWriteTransfer (event->xproperty.window,
+  transfer = write_transfers.last;
-				event->xproperty.atom);
-  if (!transfer)
-    return False;
 
-  DebugPrint ("Handling property deletion for %lu\n",
+  DebugPrint ("Handling property deletion for %lu; window %lu\n",
-	      event->xproperty.atom);
+	      event->xproperty.atom, event->xproperty.window);
+
+  while (transfer != &write_transfers)
+    {
+      last = transfer->last;
+
+      /* There can be multiple finished transfers with the same
+	 property pending deletion if a client not compliant with the
+	 ICCCM is in use.  See the large comment in
+	 HandleSelectionRequest.  */
+      DebugPrint ("Handling transfer %p\n", event);
 
       if (transfer->state & IsFinished)
 	{
 	  DebugPrint ("Completing transfer\n");
 
-      /* The transfer is now complete; finish it by freeing its data,
+	  /* The transfer is now complete; finish it by freeing its
-	 and potentially writing zero-length data.  */
+	     data, and potentially writing zero-length data.  */
 	  FreeTransfer (transfer);
 	}
       else if (transfer->state & IsWaitingForIncr)
 	{
-      /* If transfer is waiting for the INCR property to be deleted, mark
+	  /* If transfer is waiting for the INCR property to be
-	 it as started, and flush it again to write the first piece of
+	     deleted, mark it as started, and flush it again to write
-	 property data.  */
+	     the first piece of property data.  */
 
 	  DebugPrint ("Starting transfer in response to INCR property deletion\n");
 
@@ -1650,6 +1706,9 @@ HandlePropertyDelete (XEvent *event)
 	    }
 	}
 
+      transfer = last;
+    }
+
   return True;
 }
 
@@ -1658,6 +1717,22 @@ HandlePropertyNotify (XEvent *event)
 {
   ReadTransfer *transfer;
 
+  if (event->xproperty.window != DefaultRootWindow (compositor.display))
+    /* Xlib selects for PropertyNotifyMask on the root window, which
+       results in a lot of noise here.  */
+    DebugPrint ("PropertyNotify event:\n"
+		"serial:\t%lu\n"
+		"window:\t%lu\n"
+		"atom:\t%lu\n"
+		"time:\t%lu\n"
+		"state:\t%s\n",
+		event->xproperty.serial,
+		event->xproperty.window,
+		event->xproperty.atom,
+		event->xproperty.time,
+		(event->xproperty.state == PropertyNewValue
+		 ? "PropertyNewValue" : "PropertyDelete"));
+
   if (event->xproperty.state != PropertyNewValue)
     return HandlePropertyDelete (event);
 

xdata.c

@@ -245,14 +245,14 @@ static DataConversion data_conversions[] =
   };
 
 /* The time of the last X selection change.  */
-static Time last_x_selection_change;
+static Timestamp last_x_selection_change;
 
 /* The time ownership was last asserted over CLIPBOARD, and the last
    time any client did that.  */
-static Time last_clipboard_time, last_clipboard_change;
+static Timestamp last_clipboard_time, last_clipboard_change;
 
 /* The last time ownership over PRIMARY changed.  */
-static Time last_primary_time;
+static Timestamp last_primary_time;
 
 /* The currently supported selection targets.  */
 static Atom *x_selection_targets;
@@ -688,7 +688,7 @@ PostReceiveDirect (Time time, Atom selection, Atom target, int fd)
 static void PostReceiveConversion (Time, Atom, Atom, int);
 
 #define ReceiveBody(selection, primary)					\
-  Time time;								\
+  Timestamp time;							\
   TargetMapping *translation;						\
 									\
   DebugPrint ("Receiving %s from X " #selection " \n",			\
@@ -696,7 +696,7 @@ static void PostReceiveConversion (Time, Atom, Atom, int);
 									\
   /* Cast to intptr_t to silence warnings when the pointer type is	\
      larger than long.  */						\
-  time = (Time) (intptr_t) wl_resource_get_user_data (resource);	\
+  time = *(Timestamp *) wl_resource_get_user_data (resource);		\
 									\
   /* Find which selection target corresponds to MIME_TYPE.  */		\
   translation = FindTranslationForMimeType (mime_type, primary);	\
@@ -705,11 +705,11 @@ static void PostReceiveConversion (Time, Atom, Atom, int);
     {									\
       if (!translation->translation_func)				\
 	/* If a corresponding target exists, ask to receive it.  */	\
-	PostReceiveDirect (time, selection,				\
+	PostReceiveDirect (time.milliseconds, selection,	       	\
 			   MappingAtom (translation), fd);		\
       else								\
 	/* Otherwise, use the translation function.  */			\
-	translation->translation_func (time, selection,			\
+	translation->translation_func (time.milliseconds, selection,	\
 				       MappingAtom (translation),	\
 				       fd);				\
     }									\
@@ -753,8 +753,29 @@ static const struct wl_data_offer_interface wl_data_offer_impl =
     .set_actions = SetActions,
   };
 
+static void
+HandleOfferResourceDestroy (struct wl_resource *resource)
+{
+  Timestamp *timestamp;
+
+  timestamp = wl_resource_get_user_data (resource);
+
+  XLFree (timestamp);
+}
+
+static Timestamp *
+AllocateTimestamp (Timestamp timestamp)
+{
+  Timestamp *data;
+
+  data = XLMalloc (sizeof *data);
+  *data = timestamp;
+
+  return data;
+}
+
 static struct wl_resource *
-CreateOffer (struct wl_client *client, Time time)
+CreateOffer (struct wl_client *client, Timestamp time)
 {
   struct wl_resource *resource;
 
@@ -768,7 +789,8 @@ CreateOffer (struct wl_client *client, Time time)
   /* Otherwise, set the user_data to the time of the selection
      change.  */
   wl_resource_set_implementation (resource, &wl_data_offer_impl,
-				  (void *) time, NULL);
+				  AllocateTimestamp (time),
+				  HandleOfferResourceDestroy);
   return resource;
 }
 
@@ -786,7 +808,7 @@ static struct zwp_primary_selection_offer_v1_interface primary_offer_impl =
   };
 
 static struct wl_resource *
-CreatePrimaryOffer (struct wl_client *client, Time time)
+CreatePrimaryOffer (struct wl_client *client, Timestamp time)
 {
   struct wl_resource *resource;
 
@@ -800,7 +822,8 @@ CreatePrimaryOffer (struct wl_client *client, Time time)
   /* Otherwise, set the user_data to the time of the selection
      change.  */
   wl_resource_set_implementation (resource, &primary_offer_impl,
-				  (void *) time, NULL);
+				  AllocateTimestamp (time),
+				  HandleOfferResourceDestroy);
   return resource;
 }
 
@@ -883,9 +906,9 @@ SendOffers1 (struct wl_resource *resource, int ntargets, Atom *targets,
 }
 
 static void
-SendOffers (struct wl_resource *resource, Time time)
+SendOffers (struct wl_resource *resource, Timestamp time)
 {
-  if (time < last_x_selection_change)
+  if (TimestampIs (time, Earlier, last_x_selection_change))
     /* This offer is out of date.  */
     return;
 
@@ -894,9 +917,9 @@ SendOffers (struct wl_resource *resource, Time time)
 }
 
 static void
-SendPrimaryOffers (struct wl_resource *resource, Time time)
+SendPrimaryOffers (struct wl_resource *resource, Timestamp time)
 {
-  if (time < last_primary_time)
+  if (TimestampIs (time, Earlier, last_primary_time))
     /* This offer is out of date.  */
     return;
 
@@ -916,7 +939,7 @@ HandleNewSelection (Time time, Atom selection, Atom *targets,
       /* The primary selection changed, and now has the given
 	 targets.  */
 
-      if (time < last_primary_time)
+      if (TimeIs (time, Earlier, last_primary_time))
 	{
 	  XLFree (targets);
 	  return;
@@ -926,21 +949,21 @@ HandleNewSelection (Time time, Atom selection, Atom *targets,
       XLFree (x_primary_targets);
       x_primary_targets = targets;
       num_x_primary_targets = ntargets;
-      last_primary_time = time;
+      last_primary_time = TimestampFromClientTime (time);
 
       /* Add the right functions and set them as the foreign primary
 	 selection handler at TIME.  */
       funcs.create_offer = CreatePrimaryOffer;
       funcs.send_offers = SendPrimaryOffers;
 
-      XLSetForeignPrimary (time, funcs);
+      XLSetForeignPrimary (last_primary_time, funcs);
       return;
     }
 
   /* Else, the selection that changed is CLIPBOARD.  */
   
   /* Ignore outdated selection changes.  */
-  if (time < last_x_selection_change)
+  if (TimeIs (time, Earlier, last_x_selection_change))
     {
       /* We are responsible for deallocating targets.  */
       XLFree (targets);
@@ -953,7 +976,7 @@ HandleNewSelection (Time time, Atom selection, Atom *targets,
   x_selection_targets = targets;
   num_x_selection_targets = ntargets;
 
-  last_x_selection_change = time;
+  last_x_selection_change = TimestampFromClientTime (time);
 
   /* Add the right functions and set them as the foreign selection
      handler at TIME.  */
@@ -961,7 +984,7 @@ HandleNewSelection (Time time, Atom selection, Atom *targets,
   funcs.create_offer = CreateOffer;
   funcs.send_offers = SendOffers;
 
-  XLSetForeignSelection (time, funcs);
+  XLSetForeignSelection (last_x_selection_change, funcs);
 }
 
 static void
@@ -1071,13 +1094,13 @@ static void
 NoticeClipboardCleared (Time time)
 {
   /* Ignore outdated events.  */
-  if (time < last_x_selection_change)
+  if (TimeIs (time, Earlier, last_x_selection_change))
     return;
 
   DebugPrint ("CLIPBOARD was cleared at %lu\n", time);
 
-  last_x_selection_change = time;
+  last_x_selection_change = TimestampFromServerTime (time);
-  XLClearForeignSelection (time);
+  XLClearForeignSelection (last_x_selection_change);
 
   /* Free data that is no longer used.  */
   XLFree (x_selection_targets);
@@ -1089,13 +1112,13 @@ static void
 NoticePrimaryCleared (Time time)
 {
   /* Ignore outdated events.  */
-  if (time < last_primary_time)
+  if (TimeIs (time, Earlier, last_primary_time))
     return;
 
   DebugPrint ("PRIMARY was cleared at %lu\n", time);
 
-  last_primary_time = time;
+  last_primary_time = TimestampFromServerTime (time);
-  XLClearForeignPrimary (time);
+  XLClearForeignPrimary (last_primary_time);
 
   /* Free data that is no longer used.  */
   XLFree (x_primary_targets);
@@ -1111,14 +1134,16 @@ HandleSelectionNotify (XFixesSelectionNotifyEvent *event)
     return;
 
   if (event->selection == CLIPBOARD
-      && event->selection_timestamp > last_clipboard_change)
+      && 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 = event->selection_timestamp;
+    last_clipboard_change
+      = TimestampFromServerTime (event->selection_timestamp);
 
   if (event->selection == XA_PRIMARY
-      && event->selection_timestamp > last_primary_time)
+      && TimeIs (event->selection_timestamp, Later, last_primary_time))
-    last_primary_time = event->selection_timestamp;
+    last_primary_time
+      = TimestampFromServerTime (event->selection_timestamp);
 
   if (event->owner != None
       && event->selection == CLIPBOARD)
@@ -1957,9 +1982,10 @@ XLNoteSourceDestroyed (DataSource *source)
 {
   if (source == selection_data_source)
     {
-      DebugPrint ("Disowning CLIPBOARD at %lu (vs. last change %lu)\n"
+      DebugPrint ("Disowning CLIPBOARD at %u (vs. last change %u)\n"
 		  "This is being done in response to the source being destroyed.\n",
-		  last_clipboard_time, last_x_selection_change);
+		  last_clipboard_time.milliseconds,
+		  last_x_selection_change.milliseconds);
 
       /* Disown the selection.  */
       DisownSelection (CLIPBOARD);
@@ -2006,15 +2032,15 @@ FindTargetInArray (Atom *targets, int ntargets, Atom atom)
    macros...  */
 
 #define NoteLocalSelectionBody(callback, time_1, time_2, atom, field, foreign, n_foreign)	\
-  Time time;											\
+  Timestamp time;										\
   Atom *targets;										\
   int ntargets, i, n_data_conversions;								\
   Bool rc;											\
 												\
   if (source == NULL)										\
     {												\
-      DebugPrint ("Disowning " #atom " at %lu (vs. last change %lu)\n",				\
+      DebugPrint ("Disowning " #atom " at %u (vs. last change %u)\n",				\
-		  time_1, time_2);								\
+		  time_1.milliseconds, time_2.milliseconds);					\
 												\
       /* Disown the selection.  */								\
       DisownSelection (atom);									\
@@ -2022,18 +2048,19 @@ FindTargetInArray (Atom *targets, int ntargets, Atom atom)
 												\
       /* Return whether or not the selection was actually					\
 	 disowned.  */										\
-      return time_1 >= time_2;									\
+      return TimestampIs (time_1, Later, time_2);						\
     }												\
 												\
   time = XLSeatGetLastUserTime (seat);								\
 												\
-  DebugPrint ("Acquiring ownership of " #atom " at %lu\n", time);				\
+  DebugPrint ("Acquiring ownership of " #atom " at %u\n", time.milliseconds);			\
 												\
-  if (!time)											\
+  if (!time.months && !time.milliseconds)							\
     /* Nothing has yet happened on the seat.  */						\
     return False;										\
 												\
-  if (time < time_1 || time < time_2)								\
+  if (TimestampIs (time, Earlier, time_1)							\
+      || TimestampIs (time, Earlier, time_2))							\
     /* TIME is out of date.  */									\
     return False;										\
 												\
@@ -2081,7 +2108,7 @@ FindTargetInArray (Atom *targets, int ntargets, Atom atom)
   /* And own the selection.  */									\
   field = source;										\
 												\
-  rc = OwnSelection (time, atom, callback, targets, ntargets);					\
+  rc = OwnSelection (time.milliseconds, atom, callback, targets, ntargets);			\
   XLFree (targets);										\
   return rc											\