improved output formatting

bin/simple-apt-update

@@ -112,9 +112,12 @@ class UpdateWindow(Gtk.ApplicationWindow):
         self.buffer.insert(iter, text + "\n")
 
     def execute(self, args, ignore_stderr=False, output_msg=None,
-                empty_msg=None, env={}):
+                empty_msg=None, env={}, clear=True):
         self.lock()
-        self.clear()
+
+        if clear:
+            self.clear()
+
         self.output_msg = output_msg
         self.empty_msg = empty_msg
         self.ignore_stderr = ignore_stderr
@@ -176,19 +179,20 @@ class UpdateWindow(Gtk.ApplicationWindow):
     def on_upgrade(self, *args):
         self.upgrade()
 
-    def update(self):
+    def update(self, clear=True):
         args = ['/usr/bin/apt-get', '-y', 'update']
         env = {'DEBIAN_FRONTEND': 'noninteractive'}
-        self.execute(args, env=env)
+        self.execute(args, env=env, clear=clear)
 
     def on_update(self, *args):
         self.update()
 
-    def list(self):
+    def list(self, clear=True):
         args = ['/usr/bin/apt', '-qq', 'list', '--upgradable']
         self.execute(
             args,
             ignore_stderr=True,
+            clear=clear,
             output_msg="Found the following package upgrades:",
             empty_msg="Currently there are no available package upgrades.")
 
@@ -201,13 +205,12 @@ class UpdateWindow(Gtk.ApplicationWindow):
     def update_buffer(self):
         try:
             text = self.stdout_queue.get(block=False)
-
-            self.stdout += text
-            self.append_mesg("STDOUT", text)
-
             match = re.fullmatch(r'EXIT (\d+)', text)
 
-            if match is not None:
+            if match is None:
+                self.stdout += text
+                self.append_mesg("STDOUT", text)
+            else:
                 exit_code = int(match.group(1))
 
                 if exit_code != 0:
@@ -337,6 +340,8 @@ class SimpleAptUpdate(Gtk.Application):
 
         self.window.present()
         self.window.show_all()
+        self.window.update()
+        self.window.list(clear=False)
 
 
 ##