Add locking for sequence widget drags.

Timeline/Sequence_Widget.C

@@ -78,6 +78,32 @@ Sequence_Widget::set ( Log_Entry &e )
 
 }
 
+void
+Sequence_Widget::begin_drag ( const Drag &d )
+{
+    _drag = new Drag( d );
+    _r = new Range( _range );
+}
+
+void
+Sequence_Widget::end_drag ( void )
+{
+    timeline->wrlock();
+
+    /* swap in the new value */
+    _range = *_r;
+
+    timeline->unlock();
+
+    /* TODO: perhaps trigger rebuffer here? */
+
+    delete _r;
+    _r = &_range;
+
+    delete _drag;
+    _drag = NULL;
+}
+
 /** set position of widget on the timeline. */
 void
 Sequence_Widget::start ( nframes_t where )

Timeline/Sequence_Widget.H

@@ -263,21 +263,8 @@ public:
 
 //    static void pushed ( Sequence_Widget *w ) { Sequence_Widget::_pushed = w; }
 
-    void begin_drag ( const Drag &d )
-        {
-            _drag = new Drag( d );
-            _r = new Range( _range );
-        }
-
-    void end_drag ( void )
-        {
-            _range = *_r;
-            delete _r;
-            _r = &_range;
-
-            delete _drag;
-            _drag = NULL;
-        }
+    void begin_drag ( const Drag &d );
+    void end_drag ( void );
 
     int dispatch ( int m );