wasp: manager: make sleep() and background() callbacks optional

Making callbacks optional reduces pointless boilerplate in applications.

wasp/apps/clock.py

@@ -35,19 +35,15 @@ class ClockApp():
         self.draw()
         wasp.system.request_tick(1000)
 
-    def tick(self, ticks):
-        self.update()
-
-    def background(self):
-        """De-activate the application (without losing state)."""
-        pass
-
     def sleep(self):
         return True
 
     def wake(self):
         self.update()
 
+    def tick(self, ticks):
+        self.update()
+
     def draw(self):
         """Redraw the display from scratch."""
         draw = wasp.watch.drawable

wasp/apps/flashlight.py

@@ -11,7 +11,6 @@ class FlashlightApp(object):
 
     def foreground(self):
         """Activate the application."""
-        self.on_screen = ( -1, -1, -1, -1, -1, -1 )
         self.draw()
         wasp.system.request_tick(1000)
 
@@ -22,13 +21,9 @@ class FlashlightApp(object):
         """De-activate the application (without losing state)."""
         wasp.system.brightness = self._brightness
 
-    def sleep(self):
-        return False
-
     def tick(self, ticks):
         wasp.system.keep_awake()
 
     def draw(self):
         """Redraw the display from scratch."""
-        display = wasp.watch.display
-        display.fill(0xffff)
+        wasp.watch.display.fill(0xffff)

wasp/apps/testapp.py

@@ -20,13 +20,6 @@ class TestApp():
                                   wasp.EventMask.SWIPE_UPDOWN |
                                   wasp.EventMask.BUTTON)
 
-    def background(self):
-        """De-activate the application (without losing state)."""
-        pass
-
-    def sleep(self):
-        return False
-
     def press(self, button, state):
         draw = wasp.watch.drawable
         if self.test == 'Touch':

wasp/wasp.py

@@ -115,7 +115,8 @@ class Manager():
         """Switch to the requested application.
         """
         if self.app:
-            self.app.background()
+            if 'background' in dir(self.app):
+                self.app.background()
         else:
             # System start up...
             watch.display.poweron()
@@ -186,7 +187,7 @@ class Manager():
         """Enter the deepest sleep state possible.
         """
         watch.backlight.set(0)
-        if not self.app.sleep():
+        if 'sleep' not in dir(self.app) or not self.app.sleep():
             self.switch(self.applications[0])
             self.app.sleep()
         watch.display.poweroff()