change dial face to only move small triangle to improve performance

thermopi/screen.py

@@ -1,3 +1,5 @@
+import math
+
 import pygame
 import os
 
@@ -13,23 +15,28 @@ class Dial(pygame.sprite.Sprite):
     def __init__(self):
         super().__init__()
         self._base_image = pygame.image.load(script_dir + '/resources/dial-face.png')
-        self.rotation = 0
-        self.image = pygame.transform.rotate(self._base_image, 77-(2*77.5*self.rotation))
+        self.position = 0
+        self.rotation = 77 - (2 * 77.5 * self.position)
+        self.image = pygame.transform.rotate(self._base_image, self.rotation)
         self.rect = self._base_image.get_rect()
         self.test_cw = True
+
     def update(self):
         if self.test_cw:
-            self.rotation += 0.01
+            self.position += 0.01
         else:
-            self.rotation -= 0.01
-        if self.rotation > 1:
-            self.rotation = 1
+            self.position -= 0.01
+        if self.position > 1:
+            self.position = 1
             self.test_cw = not self.test_cw
-        if self.rotation < 0:
-            self.rotation = 0
+        if self.position < 0:
+            self.position = 0
             self.test_cw = not self.test_cw
-        self.image = pygame.transform.rotate(self._base_image, 77-(2*77.5*self.rotation))
+        self.rotation = 77 - (2 * 77.5 * self.position)
+        self.image = pygame.transform.rotate(self._base_image, self.rotation)
         self.rect = self.image.get_rect(center=self.rect.center)
+        self.rect.center = (math.sin(math.radians(self.rotation)) * -300 + 360,
+                            math.cos(math.radians(self.rotation + 180)) * 300 + 360)
 
 
 def main(windowed_mode):