debug-viewer: Copy log files in temporaries before using them

They are mmap'ed and it gets wrong if the file is changed.
There is high probablility the user will generate new logs while
inspecting some logs in the same file

debug-viewer/GstDebugViewer/GUI/window.py

@@ -20,6 +20,9 @@
 """GStreamer Debug Viewer GUI module."""
 
 import os.path
+import tempfile
+import shutil
+
 from bisect import bisect_right, bisect_left
 import logging
 
@@ -231,6 +234,7 @@ class Window (object):
         self.logger = logging.getLogger("ui.window")
         self.app = app
 
+        self.tmpfile = None
         self.dispatcher = None
         self.info_widget = None
         self.progress_dialog = None
@@ -937,6 +941,7 @@ class Window (object):
         if self.log_file is not None:
             for feature in self.features:
                 feature.handle_detach_log_file(self, self.log_file)
+            self.tmpfile = None
 
         if filename is None:
             if self.dispatcher is not None:
@@ -945,6 +950,9 @@ class Window (object):
             self.log_file = None
             self.actions.groups["RowActions"].props.sensitive = False
         else:
+            self.tmpfile = tempfile.NamedTemporaryFile()
+            shutil.copyfile(filename, self.tmpfile.name)
+            filename = self.tmpfile.name
             self.logger.debug("setting log file %r", filename)
 
             try: