Add rotatability to sprites.

ppb/sprites.py

@@ -140,7 +140,34 @@ def _attribute_gate(self, attribute, bad_sides):
             raise AttributeError(message)
 
 
-class BaseSprite(EventMixin):
+class Rotatable:
+    """
+    A simple rotation mixin. Can be included with sprites.
+    """
+    _rotation = 0
+    # This is necessary to make facing do the thing while also being adjustable.
+    basis = Vector(0, -1)
+    # Considered making basis private, the only reason to do so is to
+    # discourage people from relying on it as data.
+
+    @property
+    def facing(self):
+        return Vector(*self.basis).rotate(self.rotation).normalize()
+
+    @property
+    def rotation(self):
+        return self._rotation
+
+    @rotation.setter
+    def rotation(self, value):
+        self._rotation = value % 360
+
+    def rotate(self, degrees):
+        """Rotate the sprite by a given angle (in degrees)."""
+        self.rotation += degrees
+
+
+class BaseSprite(EventMixin, Rotatable):
     """
     The base Sprite class. All sprites should inherit from this (directly or
     indirectly).
@@ -155,7 +182,6 @@ class BaseSprite(EventMixin):
     image = None
     resource_path = None
     position: Vector = Vector(0, 0)
-    facing: Vector = Vector(0, -1)
     size: Union[int, float] = 1
 
     def __init__(self, **kwargs):
@@ -164,15 +190,14 @@ def __init__(self, **kwargs):
         # Make these instance properties with fresh instances
         # Don't use Vector.convert() because we need copying
         self.position = Vector(*self.position)
-        self.facing = Vector(*self.facing)
 
         # Initialize things
         for k, v in kwargs.items():
             # Abbreviations
             if k == 'pos':
                 k = 'position'
             # Castings
-            if k in ('position', 'facing'):
+            if k == 'position':
                 v = Vector(*v)  # Vector.convert() when that ships.
             setattr(self, k, v)
 
@@ -226,9 +251,6 @@ def bottom(self, value):
     def _offset_value(self):
         return self.size / 2
 
-    def rotate(self, degrees: Number):
-        self.facing.rotate(degrees)
-
     def __image__(self):
         if self.image is None:
             self.image = f"{type(self).__name__.lower()}.png"

ppb/systems/__init__.py

@@ -78,9 +78,9 @@ def prepare_resource(self, game_object):
             self.register_renderable(game_object)
 
         source_image = self.resources[game_object.image]
-        final_image = self.resize_image(source_image, game_object.size)
-        # TODO: Rotate Image to facing.
-        return final_image
+        resized_image = self.resize_image(source_image, game_object.size)
+        rotated_image = self.rotate_image(resized_image, game_object.rotation)
+        return rotated_image
 
     def prepare_rectangle(self, resource, game_object, camera):
         rect = resource.get_rect()
@@ -122,6 +122,10 @@ def resize_image(self, image, game_unit_size):
         self.resized_images[key] = resized_image
         return resized_image
 
+    def rotate_image(self, image, rotation):
+        """Rotates image counter-clockwise {rotation} degrees."""
+        return pygame.transform.rotate(image, -rotation)
+
     def target_resolution(self, width, height, game_unit_size):
         values = [width, height]
         short_side_index = width > height

tests/test_sprites.py

@@ -1,6 +1,7 @@
 from unittest import TestCase
 
 from ppb import BaseSprite, Vector
+from ppb.sprites import Rotatable
 
 
 class TestBaseSprite(TestCase):
@@ -291,3 +292,45 @@ class TestSprite(BaseSprite):
         size = 1.1
 
     assert TestSprite().left < -0.5
+
+
+def test_rotatable_instatiation():
+    rotatable = Rotatable()
+    assert rotatable.rotation == 0
+
+
+def test_rotatable_subclass():
+
+    class TestRotatable(Rotatable):
+        _rotation = 180
+        basis = Vector(0, 1)
+
+    rotatable = TestRotatable()
+    assert rotatable.rotation == 180
+    assert rotatable.facing == Vector(0, -1)
+
+
+def test_rotatable_rotation_setter():
+    rotatable = Rotatable()
+
+    rotatable.rotation = 405
+    assert rotatable.rotation == 45
+
+
+def test_rotatable_rotate():
+    rotatable = Rotatable()
+
+    assert rotatable.rotation == 0
+    rotatable.rotate(180)
+    assert rotatable.rotation == 180
+    rotatable.rotate(200)
+    assert rotatable.rotation == 20
+    rotatable.rotate(-300)
+    assert rotatable.rotation == 80
+
+
+def test_rotatable_base_sprite():
+    test_sprite = BaseSprite()
+
+    test_sprite.rotate(1)
+    assert test_sprite.rotation == 1