in a kivy scatter with background image, only part of the image is dragable

image location

Images to go with this are on google drive
==========================================


boring-bg.jpg

big background image (almost 800Kb), no useful content but created similarly to our actual backgrounds
https://drive.google.com/file/d/0B7pjQZ7_MEk5M2o0WlFuX2YzNDQ/view?usp=sharing



football_PNG1082.png

small football icon, our objects are full color but created in similar ways
https://drive.google.com/file/d/0B7pjQZ7_MEk5QS1TekpUUW0yc1k/view?usp=sharing

scatterproblem.py

from kivy.config import Config
# this determines the size of the dragable box on the scatter, it seems
Config.set('graphics', 'width', '800')
Config.set('graphics', 'height', '600')

from kivy.app import App
from kivy.uix.image import Image
from kivy.core.window import Window
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.scatter import Scatter
from kivy.uix.button import Button


class SceneScreen(App):
    def build(self):
        scatter = Scatter(#size=(3840, 2160), no effect
                          # pos=(100, 100), no effect
                          auto_bring_to_front=False,
                          do_rotation=False)

        # background image:
        img = Image(source="boring-bg.jpg", 
                    pos=(0, 0),
                    size=(3840, 2160), #, <- CRUCIAL setting this will
                    # limit the dragable region to the size of the
                    # initial window, projected onto the background
                    # image (using scale, result appr 700x600 px)
                    # HOWEVER with size unset, the full background
                    # image is a dragable region, and in fact some
                    # area around it.  However, the other 2 assets
                    # disappear off the window
                    size_hint=(None, None))
        scatter.add_widget(img)

        # with the image size above unset, this appears at very large scale and well
        # above the background image.
        obj = Image(source="football_PNG1082.png", 
                    pos=(110, 110),
                    size_hint=(None, None))
        scatter.add_widget(obj)

        obj2 = Image(source="football_PNG1082.png", 
                    pos=(1130, 2160 - 352),
                    size_hint=(None, None))
        scatter.add_widget(obj2)

        obj3 = Button(text="Click me", pos=(20,500), size=(150,150))
        scatter.add_widget(obj3)

        obj4 = Button(text="Click me too", pos=(1500,1500), size=(150,150))
        scatter.add_widget(obj4)

        from kivy.graphics.transformation import Matrix
        optscale = min(Window.height / img.height, 
                       Window.width / img.width)
        print "Scaling to", optscale
        mat = Matrix().scale(optscale, optscale, optscale) 
        scatter.apply_transform(mat)        
        # scatter.bbox = ((0,0),(80,60))  # setting this crashes kivy

        float = FloatLayout(pos=(0, 0))
        float.add_widget(scatter)
        scatter.size = Window.size
        return float

SceneScreen().run()

I ended up getting this to work, however in slightly different source. I haven't had the time yet to retest this with modifications, but in a nutshell:

• make sure the scatter is not wrapped in a boxlayout , or something that may squish it.
• do not use the transforms (scatter.apply_transform(mat) ) as they seem to shrink the touch area