lemonbar: Use condition to wake up datetime thread

.i3/lemonbar/i3_lemonbar_modules.py

@@ -79,19 +79,37 @@ class DateTimeModule(LemonModule):
 
     def _start_module(self):
         class DateTimeThread(threading.Thread):
-            def __init__(self):
+            def __init__(self, secs_mode = False):
+                self.secs_mode = secs_mode
                 self.last_out = ''
+                self.w_condition = threading.Condition()
                 self.out_queue = queue.Queue()
                 self.out_queue.readline = self.out_queue.get
                 super().__init__()
 
             def run(self):
                 while True:
-                    timestr = time.strftime("%a %d %b %H:%M:%S", time.gmtime())
+                    fmt = "%a %d %b %H:%M:%S" if self.secs_mode else "%a %d %b %H:%M"
+                    timestr = time.strftime(fmt, time.gmtime())
                     if timestr != self.last_out:
                         self.last_out = timestr
                         self.out_queue.put('{}\n'.format(timestr))
-                    time.sleep(0.1)
+                    self.sleep_until_change()
+
+            def sleep_until_change(self):
+                # Sleep for an appropriate amount of time (depending on if showing seconds or not)
+                # with the possibility of being woken early
+                if self.secs_mode:
+                    rem = 0.1
+                else:
+                    rem = time.time() % 5.0 # 5 seconds, 60 is unnecessarily long
+                self.w_condition.acquire()
+                self.w_condition.wait(rem)
+
+            def wake(self):
+                self.w_condition.acquire()
+                self.w_condition.notify()
+                self.w_condition.release()
 
         self.dt_thread = DateTimeThread()
         self.dt_thread.start()
@@ -118,7 +136,7 @@ class DateTimeModule(LemonModule):
     def _parse_data(self, data):
         # Date and time
         self.date.items = [(config.icon_clock, ' '.join(data[0:3]))]
-        self.time.items = [('', data[3] if self.show_secs else data[3][:-3])]
+        self.time.items = [('', data[3])]
 
     def date_comm(self):
         subprocess.Popen(['yad', '--no-buttons', '--calendar', '--sticky'
@@ -126,7 +144,8 @@ class DateTimeModule(LemonModule):
             , '--close-on-unfocus'])
 
     def toggle_secs(self):
-        self.show_secs = not self.show_secs
+        self.dt_thread.secs_mode = not self.dt_thread.secs_mode
+        self.dt_thread.wake()
 
 class ConkyFastModule(LemonModule):
     conky_config_str = """