ProgressSpinner using fontello

progressspinner.py

'''
Font-based ProgressSpinner
==========================
'''

from kivy.lang import Builder
from kivy.properties import NumericProperty, BooleanProperty, StringProperty
from kivy.clock import Clock
from kivy.uix.widget import Widget


Builder.load_string("""
<ProgressSpinner>:
	canvas.before:
		PushMatrix
		Rotate:
			origin: self.center
			axis: 0, 0, 1
			angle: self.rotation
	canvas.after:
		PopMatrix

	Label:
		font_name: "images/fontello.ttf"
		pos: root.pos
		size: root.size
		text: root.symbol
		font_size: sp(24)
""")


class ProgressSpinner(Widget):
	rotation = NumericProperty()
	auto_start = BooleanProperty(True)
	symbol = StringProperty(u"\ue80a")

	def on_opacity(self, instance, value):
		if not value:
			self.stop_spinning()
		elif self.auto_start:
			self.start_spinning()

	def on_parent(self, instance, value):
		if value is None:
			self.stop_spinning()
		elif self.auto_start:
			self.start_spinning()

	def start_spinning(self):
		Clock.unschedule(self._rotate)
		Clock.schedule_interval(self._rotate, 1 / 30.)

	def stop_spinning(self):
		Clock.unschedule(self._rotate)

	def _rotate(self, dt):
		self.rotation += dt * -180.