Merge pull request #509 from nilaybhatia/val-tracker-increment

FEAT : Add increment using += support for ValueTracker

Author: leotrs

docs/source/changelog.rst

@@ -62,6 +62,7 @@ Mobjects, Scenes, and Animations
 #. Add a :code:`Variable` class for displaying text that continuously updates to reflect the value of a python variable.
 #. The ``Tex`` and ``MathTex`` objects allow you to specify a custom TexTemplate using the ``template`` keyword argument.
 #. :code:`VGroup` now supports printing the class names of contained mobjects and :code:`VDict` supports printing the internal dict of mobjects
+#. :code:`ValueTracker` now supports increment using the `+=` operator (in addition to the already existing `increment_value` method)
 
 
 Documentation

manim/mobject/value_tracker.py

@@ -57,6 +57,10 @@ def set_value(self, value):
     def increment_value(self, d_value):
         self.set_value(self.get_value() + d_value)
 
+    def __iadd__(self, d_value):
+        self.increment_value(d_value)
+        return self
+
     def interpolate(self, mobject1, mobject2, alpha, path_func=straight_path):
         """
         Turns self into an interpolation between mobject1

tests/test_value_tracker.py

@@ -0,0 +1,28 @@
+from manim.mobject.value_tracker import ValueTracker
+
+
+def test_value_tracker_set_value():
+    """Test ValueTracker.set_value()"""
+    tracker = ValueTracker()
+    tracker.set_value(10.0)
+    assert tracker.get_value() == 10.0
+
+
+def test_value_tracker_get_value():
+    """Test ValueTracker.get_value()"""
+    tracker = ValueTracker(10.0)
+    assert tracker.get_value() == 10.0
+
+
+def test_value_tracker_increment_value():
+    """Test ValueTracker.increment_value()"""
+    tracker = ValueTracker(0.0)
+    tracker.increment_value(10.0)
+    assert tracker.get_value() == 10.0
+
+
+def test_value_tracker_iadd():
+    """Test ValueTracker.__iadd__()"""
+    tracker = ValueTracker(0.0)
+    tracker += 10.0
+    assert tracker.get_value() == 10.0