[client] clipboard: add transport provider interface

Route clipboard exchange through a provider interface. Connected
transports take priority while SPICE remains the fallback.

Track asynchronous X11 and Wayland transfers by request, preserving
clipboard ownership across provider changes.

Use PureSpice clipboard status notifications for capability and
lifecycle updates.

client/displayservers/Wayland/wayland.h

@@ -59,14 +59,16 @@
 #include "motion.h"
 
 typedef void (*WaylandPollCallback)(uint32_t events, void * opaque);
+typedef void (*WaylandPollCleanup)(void * opaque);
 
 struct WaylandPoll
 {
-  int fd;
-  bool removed;
+  int                 fd;
+  atomic_bool         removed;
   WaylandPollCallback callback;
-  void * opaque;
-  struct wl_list link;
+  WaylandPollCleanup  cleanup;
+  void              * opaque;
+  struct wl_list      link;
 };
 
 struct OutputColorDescription;
@@ -273,40 +275,39 @@ struct WaylandDSState
 
   struct wl_list poll; // WaylandPoll::link
   struct wl_list pollFree; // WaylandPoll::link
-  LG_Lock pollLock;
-  LG_Lock pollFreeLock;
-  int epollFd;
-  int displayFd;
+  LG_Lock        pollLock;
+  LG_Lock        pollFreeLock;
+  unsigned int   pollWaiters;
+  int            epollFd;
+  int            displayFd;
 };
 
 struct WCBTransfer
 {
   struct CountedBuffer * data;
-  const char ** mimetypes;
+  const char           ** mimetypes;
 };
 
 struct ClipboardRead
 {
-  int fd;
-  size_t size;
-  size_t numRead;
-  uint8_t * buf;
-  enum LG_ClipboardData type;
-  struct wl_data_offer * offer;
+  int                    fd;
+  size_t                 size;
+  size_t                 numRead;
+  uint8_t              * buf;
+  LG_ClipboardRequest    request;
+  LG_ClipboardData       type;
 };
 
 struct WCBState
 {
   struct wl_data_device * dataDevice;
-  char lgMimetype[64];
+  char                    lgMimetype[64];
 
-  char * mimetypes[LG_CLIPBOARD_DATA_NONE];
+  char                 * mimetypes[LG_CLIPBOARD_DATA_NONE];
   struct wl_data_offer * offer;
   struct wl_data_offer * dndOffer;
 
-  bool haveRequest;
-  LG_ClipboardData type;
-
+  LG_Lock                lock;
   struct ClipboardRead * currentRead;
 };
 
@@ -320,7 +321,8 @@ void waylandActivationRequestActivation(void);
 
 // clipboard module
 bool waylandCBInit(void);
-void waylandCBRequest(LG_ClipboardData type);
+void waylandCBFree(void);
+void waylandCBRequest(LG_ClipboardRequest request, LG_ClipboardData type);
 void waylandCBNotice(LG_ClipboardData type);
 void waylandCBRelease(void);
 void waylandCBInvalidate(void);
@@ -407,8 +409,11 @@ void waylandOutputUpdateHDRWhiteLevel(void);
 
 // poll module
 bool waylandPollInit(void);
+void waylandPollFree(void);
 void waylandWait(unsigned int time);
 bool waylandPollRegister(int fd, WaylandPollCallback callback, void * opaque, uint32_t events);
+bool waylandPollRegisterWithCleanup(int fd, WaylandPollCallback callback,
+    void * opaque, WaylandPollCleanup cleanup, uint32_t events);
 bool waylandPollUnregister(int fd);
 
 // presentation module