Minor fixes to the certificate warning prompt (#2949)

- slightly lower the CPU usage (callback instead of active waiting w/ sleep)
- make the terminal beep so the user knows something happened
- prevent the user “escaping” the prompt by pressing /, s, or S

src/core/handlers.py

@@ -1196,20 +1196,7 @@ def validate_ssl(self, pem):
             self.information('New certificate found (sha-2 hash:'
                              ' %s)\nPlease validate or abort' % sha2_found_cert,
                              'Warning')
-            input = windows.YesNoInput(text="WARNING! Server certificate has changed, accept? (y/n)")
-            self.current_tab().input = input
-            input.resize(1, self.current_tab().width, self.current_tab().height-1, 0)
-            input.refresh()
-            self.doupdate()
-            old_loop = asyncio.get_event_loop()
-            new_loop = asyncio.new_event_loop()
-            asyncio.set_event_loop(new_loop)
-            new_loop.add_reader(sys.stdin, self.on_input_readable)
-            future = asyncio.Future()
-            @asyncio.coroutine
-            def check_input(future):
-                while input.value is None:
-                    yield from asyncio.sleep(0.01)
+            def check_input():
                 self.current_tab().input = saved_input
                 self.paused = False
                 if input.value:
@@ -1222,10 +1209,17 @@ def validate_ssl(self, pem):
                     self.disconnect()
                 new_loop.stop()
                 asyncio.set_event_loop(old_loop)
-            asyncio.async(check_input(future))
+            input = windows.YesNoInput(text="WARNING! Server certificate has changed, accept? (y/n)", callback=check_input)
+            self.current_tab().input = input
+            input.resize(1, self.current_tab().width, self.current_tab().height-1, 0)
+            input.refresh()
+            self.doupdate()
+            old_loop = asyncio.get_event_loop()
+            new_loop = asyncio.new_event_loop()
+            asyncio.set_event_loop(new_loop)
+            new_loop.add_reader(sys.stdin, self.on_input_readable)
+            curses.beep()
             new_loop.run_forever()
-
-
     else:
         log.debug('First time. Setting certificate to %s', sha2_found_cert)
         if not config.silent_set('certificate', sha2_found_cert):

src/tabs/rostertab.py

@@ -1012,6 +1012,8 @@ class RosterInfoTab(Tab):
         """
         '/' is pressed, we enter "input mode"
         """
+        if isinstance(self.input, windows.YesNoInput):
+            return
         curses.curs_set(1)
         self.input = windows.CommandInput("", self.reset_help_message, self.execute_slash_command)
         self.input.resize(1, self.width, self.height-1, 0)
@@ -1187,6 +1189,8 @@ class RosterInfoTab(Tab):
         Start the search. The input should appear with a short instruction
         in it.
         """
+        if isinstance(self.input, windows.YesNoInput):
+            return
         curses.curs_set(1)
         self.input = windows.CommandInput("[Search]", self.on_search_terminate, self.on_search_terminate, self.set_roster_filter)
         self.input.resize(1, self.width, self.height-1, 0)
@@ -1197,6 +1201,8 @@ class RosterInfoTab(Tab):
 
     @refresh_wrapper.always
     def start_search_slow(self):
+        if isinstance(self.input, windows.YesNoInput):
+            return
         curses.curs_set(1)
         self.input = windows.CommandInput("[Search]", self.on_search_terminate, self.on_search_terminate, self.set_roster_filter_slow)
         self.input.resize(1, self.width, self.height-1, 0)

src/windows/input_placeholders.py

@@ -41,7 +41,7 @@ class YesNoInput(Win):
     A Window just displaying a Yes/No input
     Used to ask a confirmation
     """
-    def __init__(self, text=''):
+    def __init__(self, text='', callback=None):
         Win.__init__(self)
         self.key_func = {
                 'y' : self.on_yes,
@@ -49,6 +49,7 @@ class YesNoInput(Win):
         }
         self.txt = text
         self.value = None
+        self.callback = callback
 
     def on_yes(self):
         self.value = True
@@ -68,6 +69,8 @@ class YesNoInput(Win):
     def do_command(self, key, raw=False):
         if key.lower() in self.key_func:
             self.key_func[key]()
+        if self.value is not None and self.callback is not None:
+            return self.callback()
 
     def on_delete(self):
         return