snapshot log text on GTK main thread before HDF5 dump

src/damaris/gui/DamarisGUI.py

@@ -738,7 +738,7 @@ class DamarisGUI:
         self.save_thread = None
         self.dump_filename = ""
         if actual_config[ "data_pool_name" ] != "":
-            self.dump_states( init=True )
+            self.dump_states( init=True, logtext=self.log.snapshot_since_last_dump( ) )
         
         gobject.timeout_add( 200, self.observe_running_experiment )
 
@@ -862,8 +862,10 @@ class DamarisGUI:
                 # Disable run button during data saving to prevent UI confusion
                 self.toolbar_run_button.set_sensitive(False)
 
-                # thread to save data...
-                self.save_thread = threading.Thread( target=self.dump_states, name="dump states" )
+                # thread to save data... snapshot log on the main thread first
+                self.save_thread = threading.Thread( target=self.dump_states,
+                                                     args=(False, self.log.snapshot_since_last_dump( )),
+                                                     name="dump states" )
                 self.save_thread.start( )
                 self.dump_start_time = time.time( )
                 self.dump_dots = 0
@@ -909,16 +911,19 @@ class DamarisGUI:
             logger.info("Dumping data pool")
             self.dump_start_time = time.time( )
             self.dump_dots = 0
-            # thread to save data...
-            self.dump_thread = threading.Thread( target=self.dump_states, name="dump states" )
+            # thread to save data... snapshot log on the main thread first
+            self.dump_thread = threading.Thread( target=self.dump_states,
+                                                 args=(False, self.log.snapshot_since_last_dump( )),
+                                                 name="dump states" )
             self.dump_thread.start( )
 
         # or look at them again
         return True
 
-    def dump_states( self, init=False ):
+    def dump_states( self, init=False, logtext=None ):
         """
         init: constructs basic structure of this file
+        logtext: pending log window text, captured on the GTK main thread
         compress: optional argument for zlib compression 0-9
         """
 
@@ -1091,16 +1096,7 @@ class DamarisGUI:
 
             # save log window information:
             # also save backend's logfile information?
-            # the dump thread must not race with the GUI thread appending messages
-            with self.log.lock:
-                logtextbuffer = self.log.textbuffer
-                last_end = logtextbuffer.get_mark( "lastdumped" )
-                if last_end is None:
-                    last_end = logtextbuffer.create_mark( "lastdumped", logtextbuffer.get_start_iter( ), left_gravity=True )
-                logtext_start = logtextbuffer.get_iter_at_mark( last_end )
-                logtext_end = logtextbuffer.get_end_iter( )
-                logtext = logtextbuffer.get_text( logtext_start, logtext_end, True )
-                logtextbuffer.move_mark( "lastdumped", logtext_end )
+            # logtext was snapshotted on the GTK main thread before spawning
             if logtext is not None:
                 for l in logtext.splitlines( ):
                     dump_file.root.log.append( numpy.array( [ l ], dtype="S120" ) )
@@ -1371,6 +1367,26 @@ class LogWindow:
             self.textbuffer.insert_at_cursor( date_tag + str( message ) )
             self.textview.scroll_to_mark( self.textbuffer.get_insert( ), 0.1 , False, 0.5, 0.5)
 
+    def snapshot_since_last_dump( self ):
+        """Return log text appended since the last dump and advance the mark.
+
+        Must be called from the GTK main thread. The result is plain Python
+        data that can safely be passed to the dump thread.
+
+        Examples:
+            >>> logtext = self.log.snapshot_since_last_dump( )
+        """
+        with self.lock:
+            tb = self.textbuffer
+            mark = tb.get_mark( "lastdumped" )
+            if mark is None:
+                mark = tb.create_mark( "lastdumped", tb.get_start_iter( ), left_gravity=True )
+            start = tb.get_iter_at_mark( mark )
+            end = tb.get_end_iter( )
+            text = tb.get_text( start, end, True )
+            tb.move_mark( "lastdumped", end )
+        return text
+
     def textview_keypress( self, widget, event, data=None ):
         if event.state & gdk.ModifierType.CONTROL_MASK != 0:
             if event.keyval == gdk.keyval_from_name("f"):