win32u: Use WM_WINE_CLIPCURSOR / TRUE for empty clipping rect.

dlls/win32u/message.c

@@ -1272,7 +1272,7 @@ static LRESULT handle_internal_message( HWND hwnd, UINT msg, WPARAM wparam, LPAR
         return call_current_hook( h_extra->handle, HC_ACTION, wparam, h_extra->lparam );
     }
     case WM_WINE_CLIPCURSOR:
-        return process_wine_clipcursor( !wparam );
+        return process_wine_clipcursor( wparam );
     case WM_WINE_UPDATEWINDOWSTATE:
         update_window_state( hwnd );
         return 0;

server/queue.c

@@ -468,7 +468,7 @@ static void set_clip_rectangle( struct desktop *desktop, const rectangle_t *rect
     }
     else desktop->cursor.clip = top_rect;
 
-    if (send_clip_msg) post_desktop_message( desktop, WM_WINE_CLIPCURSOR, rect != NULL, 0 );
+    if (send_clip_msg) post_desktop_message( desktop, WM_WINE_CLIPCURSOR, rect == NULL, 0 );
 
     /* warp the mouse to be inside the clip rect */
     x = max( min( desktop->cursor.x, desktop->cursor.clip.right - 1 ), desktop->cursor.clip.left );