X-Git-Url: https://git.carlh.net/gitweb/?a=blobdiff_plain;f=src%2Flib%2Fui_signaller.h;h=221bcbe9581ad2cdfaacdcaaeabf4487ab6e6723;hb=784c560e3437136d6006f8df2fb35f41585b6a8d;hp=0797d911e7123198f02f4c0fd3c061ae4dc3d9b4;hpb=63ea6b6c5ee64f8ee067c2b488d004b6dfe363e0;p=dcpomatic.git

diff --git a/src/lib/ui_signaller.h b/src/lib/ui_signaller.h
index 0797d911e..221bcbe95 100644
--- a/src/lib/ui_signaller.h
+++ b/src/lib/ui_signaller.h
@@ -22,28 +22,53 @@
 
 #include <boost/bind.hpp>
 #include <boost/asio.hpp>
+#include <boost/thread.hpp>
 
+/** A class to allow signals to be emitted from non-UI threads and handled
+ *  by a UI thread.
+ */
 class UISignaller
 {
 public:
+	/** Create a UISignaller.  Must be called from the UI thread */
 	UISignaller ()
 		: _work (_service)
-	{}
-	
+	{
+		_ui_thread = boost::this_thread::get_id ();
+	}
+
+	/** Emit a signal from any thread whose handlers will be called in the UI
+	 *  thread.  Use something like:
+	 *
+	 *  ui_signaller->emit (boost::bind (boost::ref (SomeSignal), parameter));
+	 */
 	template <typename T>
 	void emit (T f) {
-		_service.post (f);
+		if (boost::this_thread::get_id() == _ui_thread) {
+			/* already in the UI thread */
+			f ();
+		} else {
+			/* non-UI thread; post to the service and wake up the UI */
+			_service.post (f);
+			wake_ui ();
+		}
 	}
 
+	/** Call this in the UI when it is idle */
 	void ui_idle () {
 		_service.poll ();
 	}
 
+	/** This should wake the UI and make it call ui_idle() */
 	virtual void wake_ui () = 0;
 
 private:
+	/** A io_service which is used as the conduit for messages */
 	boost::asio::io_service _service;
+	/** Object required to keep io_service from stopping when it has nothing to do */
 	boost::asio::io_service::work _work;
+	/** The UI thread's ID */
+	boost::thread::id _ui_thread;
 };
 
 extern UISignaller* ui_signaller;