- refactored

utils/value.py

@@ -0,0 +1,32 @@
+class Value:
+	def __init__(self, initial=None):
+		self.value = initial
+		self.has_changed = True
+
+	def set(self, value):
+		self.has_changed = self.value != value
+		self.value = value
+
+	def is_changed(self):
+		return self.has_changed
+
+	def get(self):
+		self.has_changed = False
+		return self.value
+
+
+class ValueChanged(object):
+	def __init__(self, on_changed, prec=2, initial=None):
+		self.on_changed = on_changed
+		self.prec = prec
+		self.value = initial
+
+	def set(self, value):
+		has_changed = True
+		value_rounded = round(value, self.prec)
+		if self.value is not None:
+			has_changed = self.value != value_rounded
+
+		self.value = value_rounded
+		if has_changed:
+			self.on_changed(value_rounded)