effect_widget_for_fbo.py

from kivy.app import App
from kivy.lang import Builder
from kivy.factory import Factory


KV = '''
FloatLayout:
    EffectWidget:
        id: eff
        BoxLayout:
            orientation: 'vertical'
            Button:
            Button:
            TextInput:

    Image:
        texture: eff.texture
        size_hint: None, None
        pos_hint: {'right': 1, 'top': 1}
'''

class Application(App):
    def build(self):
        return Builder.load_string(KV)


if __name__ == "__main__":
    Application().run()