roundlabel.py

from kivy.lang import Builder
from kivy.properties import NumericProperty, ListProperty
from kivy.uix.label import Label

__all__ = ['RoundLabel']

KV = '''
#:import chain itertools.chain
#:import sin math.sin
#:import cos math.cos
<-RoundLabel>:
    font_size: 16
    a: self.texture_size[0] / float(self.radius)
    min_angle: self.angle - self.a / 2.

    canvas:
        Color:
            rgba: self.color
        Mesh:
            mode: 'triangle_strip'
            texture: self.texture
            vertices:
                list(chain(*[
                (
                self.origin[0] + cos(self.min_angle + a * self.a) * self.radius,
                self.origin[1] + sin(self.min_angle + a * self.a) * self.radius, 1 - float(a), 1,
                self.origin[0] + cos(self.min_angle + a * self.a) * (self.radius + self.texture_size[1]),
                self.origin[1] + sin(self.min_angle + a * self.a) * (self.radius + self.texture_size[1]), 1 - float(a), 0
                )
                for a in (x / float(self.precision) for x in range(self.precision, 0, -1))
                ]) if self.min_angle and self.radius and self.precision else [])
            indices: range(2 * self.precision)
'''  # noqa


class RoundLabel(Label):
    radius = NumericProperty(50)
    angle = NumericProperty(0)
    origin = ListProperty([0, 0])
    precision = NumericProperty(10)


Builder.load_string(KV)

KV_DEMO = r'''
#:import pi math.pi
BoxLayout:
    BoxLayout:
        orientation: 'vertical'

        RoundLabel:
            text: ti.text
            precision: precision.value
            radius: radius.value
            angle: angle.value
            font_size: font_size.value
            origin: self.center

        TextInput:
            id: ti
            multiline: False
            size_hint_y: None
            height: self.minimum_height
            text: 'default text'

    BoxLayout:
        orientation: 'vertical'
        Label:
            text: 'precision:\n {}'.format(precision.value)
        Slider:
            id: precision
            min: 1
            max: 360
            step: 1
            value: 180

        Label:
            text: 'radius:\n {}'.format(radius.value)
        Slider:
            id: radius
            min: 20
            max: 500
            step: 1
            value: 100

        Label:
            text: 'angle:\n {}'.format(angle.value)
        Slider:
            id: angle
            min: 0
            max: 2 * pi
            step: 0.01
            value: 0

        Label:
            text: 'font size:\n {}'.format(font_size.value)
        Slider:
            id: font_size
            min: 10
            max: 100
            step: 1
            value: 20
'''

if __name__ == '__main__':
    from kivy.base import runTouchApp
    from kivy.lang import Builder

    runTouchApp(Builder.load_string(KV_DEMO))