[PATCH 0/1] MR9418: winex11.drv: use proper timestamp for X11 clipboard selection

[Jiajin Cui (＠jin-king1)]

1. Replace CurrentTime with actual server timestamp in clipboard
selection ownership
2. Add get_server_time function to retrieve current X11 server timestamp
by generating PropertyNotify event
3. Store selection timestamp globally for use in export_timestamp
function
4. Maintain original window event mask when getting server time

The previous implementation used CurrentTime (0) which can cause issues
with X11 clipboard handling. Using a proper server timestamp ensures
correct synchronization and prevents potential race conditions in
clipboard ownership transfers.

Signed-off-by: Jiajin Cui

[PATCH 1/1] winex11.drv: use proper timestamp for X11 clipboard selection

[Jiajin Cui]

From: Jiajin Cui

1. Replace CurrentTime with actual server timestamp in clipboard
selection ownership
2. Add get_server_time function to retrieve current X11 server timestamp
by generating PropertyNotify event
3. Store selection timestamp globally for use in export_timestamp
function
4. Maintain original window event mask when getting server time

The previous implementation used CurrentTime (0) which can cause issues
with X11 clipboard handling. Using a proper server timestamp ensures
correct synchronization and prevents potential race conditions in
clipboard ownership transfers.

Signed-off-by: Jiajin Cui 
---
 dlls/winex11.drv/clipboard.c | 50 +++++++++++++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 4 deletions(-)

diff --git a/dlls/winex11.drv/clipboard.c b/dlls/winex11.drv/clipboard.c
index ee0015639b8..99731a9126e 100644
--- a/dlls/winex11.drv/clipboard.c
+++ b/dlls/winex11.drv/clipboard.c
@@ -193,6 +193,7 @@ static DWORD clipboard_thread_id;
 static HWND clipboard_hwnd;
 static BOOL is_clipboard_owner;
 static Window selection_window;
+static Time selection_timestamp;
 static Window import_window;
 static Atom current_selection;
 static UINT rendered_formats;
@@ -1733,7 +1734,7 @@ static BOOL export_multiple( Display *display, Window win, Atom prop, Atom targe
  */
 static BOOL export_timestamp( Display *display, Window win, Atom prop, Atom target, void *data, size_t size )
 {
-    Time time = CurrentTime;  /* FIXME */
+    Time time = selection_timestamp;
     put_property( display, win, prop, XA_INTEGER, 32, &time, 1 );
     return TRUE;
 }
@@ -1906,6 +1907,44 @@ static BOOL read_property( Display *display, Window w, Atom prop,
     return TRUE;
 }

+/**************************************************************************
+ *		get_server_time
+ *
+ * Get the current X11 server timestamp by generating a PropertyNotify event
+ */
+static Time get_server_time( Display *display, Window win )
+{
+    static Atom timestamp_prop = 0;
+    XEvent event;
+    Time timestamp = CurrentTime;
+    XWindowAttributes attrs;
+
+    if (!timestamp_prop)
+        timestamp_prop = XInternAtom( display, "__wine_timestamp", False );
+
+    /* Ensure window can receive PropertyNotify events */
+    XGetWindowAttributes( display, win, &attrs );
+    XSelectInput( display, win, attrs.your_event_mask | PropertyChangeMask );
+
+    /* Generate a PropertyNotify event to get server time */
+    XChangeProperty( display, win, timestamp_prop, XA_INTEGER, 8, PropModeReplace, NULL, 0 );
+    XSync( display, False );
+
+    /* Wait for the PropertyNotify event */
+    while (XCheckTypedWindowEvent( display, win, PropertyNotify, &event ))
+    {
+        if (event.xproperty.atom == timestamp_prop)
+        {
+            timestamp = event.xproperty.time;
+            break;
+        }
+    }
+
+    /* Restore original event mask */
+    XSelectInput( display, win, attrs.your_event_mask );
+
+    return timestamp;
+}

/**************************************************************************
  *		acquire_selection
@@ -1920,9 +1959,12 @@ static void acquire_selection( Display *display )
                                       InputOutput, CopyFromParent, 0, NULL );
     if (!selection_window) return;

-    XSetSelectionOwner( display, x11drv_atom(CLIPBOARD), selection_window, CurrentTime );
-    if (use_primary_selection) XSetSelectionOwner( display, XA_PRIMARY, selection_window, CurrentTime );
-    TRACE( "win %lx\n", selection_window );
+    /* Get the current server timestamp for selection ownership */
+    selection_timestamp = get_server_time( display, selection_window );
+
+    XSetSelectionOwner( display, x11drv_atom(CLIPBOARD), selection_window, selection_timestamp );
+    if (use_primary_selection) XSetSelectionOwner( display, XA_PRIMARY, selection_window, selection_timestamp );
+    TRACE( "win %lx timestamp %lu\n", selection_window, selection_timestamp );
 }

[Jiajin Cui (＠jin-king1)]

We can use a VMware virtual machine to test this issue. The VMware virtual machine determines whether the clipboard data has been updated by checking the timestamp.

[Esme Povirk (＠madewokherd)]

Esme Povirk (@madewokherd) commented about dlls/winex11.drv/clipboard.c:
> - XGetWindowAttributes( display, win, &attrs );
> - XSelectInput( display, win, attrs.your_event_mask | PropertyChangeMask );
> -
> - /* Generate a PropertyNotify event to get server time */
> - XChangeProperty( display, win, timestamp_prop, XA_INTEGER, 8, PropModeReplace, NULL, 0 );
> - XSync( display, False );
> -
> - /* Wait for the PropertyNotify event */
> - while (XCheckTypedWindowEvent( display, win, PropertyNotify, &event ))
> - {
> -
>    if (event.xproperty.atom == timestamp_prop)
> -
>    {
> -
>        timestamp = event.xproperty.time;
> -
>        break;
> -
>    }
> - }

This might remove unrelated events from the queue, though that won't matter for its current use case.

[Esme Povirk (＠madewokherd)]

Esme Povirk (@madewokherd) commented about dlls/winex11.drv/clipboard.c:
> }
>
> +/**************************************************************************
> -
> -
> get_server_time
> -
> -
> -
> - Get the current X11 server timestamp by generating a PropertyNotify event
> - */
>
> +static Time get_server_time( Display *display, Window win )
> +{
> - static Atom timestamp_prop = 0;
> - XEvent event;
> - Time timestamp = CurrentTime;
> - XWindowAttributes attrs;
> -
> - if (!timestamp_prop)
> -
>    timestamp_prop = XInternAtom( display, "__wine_timestamp", False );

This should probably use X11DRV_Atoms.