X-Git-Url: https://main.carlh.net/gitweb/?a=blobdiff_plain;f=libs%2Fpbd%2Fpbd%2Fcrossthread.h;h=d172c9c60f65933df348e3130ab8ea74210b5d75;hb=95ccbc452f513a9d6f70de45bc413067e568364c;hp=b815cfd31953fffa3317869dfc058e1caed46c02;hpb=87726495c30f90554b5204b5385d17274a8fe93e;p=ardour.git

diff --git a/libs/pbd/pbd/crossthread.h b/libs/pbd/pbd/crossthread.h
index b815cfd319..d172c9c60f 100644
--- a/libs/pbd/pbd/crossthread.h
+++ b/libs/pbd/pbd/crossthread.h
@@ -20,38 +20,86 @@
 #ifndef __pbd__crossthread_h__
 #define __pbd__crossthread_h__
 
-#include <pbd/abstract_ui.h>
-#include <sigc++/sigc++.h>
-#include <pthread.h>
-
-template<class RequestType> 
-void 
-call_slot_from_thread_or_dispatch_it (pthread_t thread_id, AbstractUI<RequestType>& ui, sigc::slot<void> theSlot)
-{
-	/* when called, this function will determine whether the calling thread
-	   is the same as thread specified by the first argument. if it is,
-	   the we execute the slot. if not, we ask the interface given by the second
-	   argument to call the slot.
-	*/
+#ifdef check
+#undef check
+#endif
+
+#include <glibmm/main.h>
+
+#include "pbd/libpbd_visibility.h"
+
+/** A simple abstraction of a mechanism of signalling one thread from another.
+ * The signaller calls ::wakeup() to tell the signalled thread to check for
+ * work to be done. 
+ *
+ * This implementation provides both ::selectable() for use in direct
+ * poll/select-based event loops, and a Glib::IOSource via ::ios() for use
+ * in Glib main loop based situations. 
+ */
+
+class LIBPBD_API CrossThreadChannel { 
+  public:
+	/** if @a non_blocking is true, the channel will not cause blocking
+	 * when used in an event loop based on poll/select or the glib main
+	 * loop.
+	 */
+	CrossThreadChannel(bool non_blocking);
+	~CrossThreadChannel();
+	
+	/** Tell the listening thread that is has work to do.
+	 */
+	void wakeup();
+	
+	/* if the listening thread cares about the precise message
+	 * it is being sent, then ::deliver() can be used to send
+	 * a single byte message rather than a simple wakeup. These
+	 * two mechanisms should not be used on the same CrossThreadChannel
+	 * because there is no way to know which byte value will be used
+	 * for ::wakeup()
+	 */
+        int deliver (char msg);
 
-	if (pthread_self() == thread_id) {
-		theSlot ();
-	} else {
-		ui.call_slot (theSlot);
-	}
-}
-
-template<class RequestType> 
-sigc::slot<void>
-crossthread_safe (pthread_t thread_id, AbstractUI<RequestType>& ui, sigc::slot<void> theSlot)
-{
-	/* this function returns a slot that will ensure that theSlot is either
-	   called by the specified thread or passed to the interface via 
-	   AbstractUI::call_slot().
+	/** if using ::deliver() to wakeup the listening thread, then
+	 * the listener should call ::receive() to fetch the message
+	 * type from the channel.
+	 */
+        int receive (char& msg);
+
+	/** empty the channel of all requests.
+	 * Typically this is done as soon as input 
+	 * is noticed on the channel, because the
+	 * handler will look at a separately managed work
+	 * queue. The actual number of queued "wakeups"
+	 * in the channel will not be important.
+	 */
+	void drain ();
+	static void drain (int fd);
+
+	/** File descriptor that can be used with poll/select to
+	 * detect when wakeup() has been called on this channel.
+	 * It be marked as readable/input-ready when this condition
+	 * is true. It has already been marked non-blocking.
+	 */
+	int selectable() const { return fds[0]; }
+
+	/* glibmm 2.22 and earlier has a terrifying bug that will
+	   cause crashes whenever a Source is removed from
+	   a MainContext (including the destruction of the MainContext),
+	   because the Source is destroyed "out from under the nose of" 
+	   the RefPtr. I (Paul) have fixed this (https://bugzilla.gnome.org/show_bug.cgi?id=561885)
+	   but in the meantime, we need a hack to get around the issue.
 	*/
-	   
-	return sigc::bind (sigc::ptr_fun (call_slot_from_thread_or_dispatch_it<RequestType>), 
-			   thread_id, ui, theSlot);
-}
+	Glib::RefPtr<Glib::IOSource> ios();
+	void drop_ios ();
+
+	/** returns true if the CrossThreadChannel was
+	 * correctly constructed.
+	 */
+	bool ok() const { return fds[0] >= 0 && fds[1] >= 0; }
+
+  private:
+	Glib::RefPtr<Glib::IOSource>* _ios; // lazily constructed
+	int fds[2]; // current implementation uses a pipe/fifo
+};
 
 #endif /* __pbd__crossthread_h__ */