[core/decorators] use difflib to make scrolling reset detection fuzzy

when scrolling text that is subject to *slight* changes (e.g. a song
that contains the current position within the song), allow for slight
variations in the displayed text.

fixes #629

bumblebee_status/core/decorators.py

@@ -1,3 +1,4 @@
+import difflib
 import util.format
 
 
@@ -28,7 +29,10 @@ def scrollable(func):
         if not text:
             return text
 
-        if text != widget.get("__content__", text):
+        if (
+            difflib.SequenceMatcher(a=text, b=widget.get("__content__", text)).ratio()
+            < 0.9
+        ):
             widget.set("scrolling.start", 0)
             widget.set("scrolling.direction", "right")
         widget.set("__content__", text)

tests/core/test_decorators.py

@@ -70,5 +70,16 @@ class config(unittest.TestCase):
         self.module.text = "wxyz"
         self.assertEqual("wx", self.module.get(self.widget))
 
+    def test_minimum_changed_data(self):
+        self.module.text = "this is a sample song (0:00)"
+        self.module.set("scrolling.width", 10)
+        self.assertEqual(self.module.text[0:10], self.module.get(self.widget))
+        self.module.text = "this is a sample song (0:01)"
+        self.assertEqual(self.module.text[1:11], self.module.get(self.widget))
+        self.module.text = "this is a sample song (0:12)"
+        self.assertEqual(self.module.text[2:12], self.module.get(self.widget))
+        self.module.text = "this is a different song (0:12)"
+        self.assertEqual(self.module.text[0:10], self.module.get(self.widget))
+
 
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