spicec: Move setting of clipboard_owner to guest to platform code

Atleast under x11 there is a race condition when setting the clipboard
owner to guest from the RedClient code rather then doing it in Platform.

After the XSetSelectionOwner() in Platform::on_clipboard_grab(), which runs
from the main message loop thread, the x11 event thread can receive a
SelectionRequest event from another x11 app, before the RedClient code
has set the clipboard owner, which will trigger the owner != guest
check in the SelectionRequest event handling code.

By moving the setting of the owner in to Platform::on_clipboard_grab() it
gets protected by the clipboard lock, which closes this tiny race.

1 files changed, 8 insertions, 2 deletions

diff --git a/client/x11/platform.cpp b/client/x11/platform.cpp
index 29b5f753..8f0665cb 100644
--- a/client/x11/platform.cpp
+++ b/client/x11/platform.cpp
@@ -3355,6 +3355,8 @@ bool Platform::on_clipboard_grab(uint32_t *types, uint32_t type_count)
 
     XSetSelectionOwner(x_display, clipboard_prop, platform_win, CurrentTime);
     XFlush(x_display);
+
+    set_clipboard_owner_unlocked(owner_guest);
     return true;
 }
 
@@ -3362,12 +3364,16 @@ int Platform::_clipboard_owner = Platform::owner_none;
 
 void Platform::set_clipboard_owner(int new_owner)
 {
+        Lock lock(clipboard_lock);
+        set_clipboard_owner_unlocked(new_owner);
+}
+
+void Platform::set_clipboard_owner_unlocked(int new_owner)
+{
     const char * const owner_str[] = { "none", "guest", "client" };
 
     /* Clear pending requests and clipboard data */
     {
-        Lock lock(clipboard_lock);
-
         if (next_selection_request) {
             LOG_INFO("selection requests pending upon clipboard owner change, clearing");
             while (next_selection_request)