gistfile1.txt

# Class definition of ChannelImageButton

class ChannelImageButton( ButtonBehavior, Image ):
      pass
      

# Code that is adding the ChannelImageButtons to the GridLayout in the ScrollView.

                # Get a list of images
                channels = project.get_image_channels( btn.__image_id__ )
                # Clear any widgets in the GridLayout in the ScrollView
                self.channel_scroll_view.button_list.clear_widgets( )

                # Create ChannelImageButtons, and set their texture to the image
                # Try to draw a rectangle on the buttons canvas
                for i in channels:
                        image = CoreImage( io.BytesIO( i[ 1 ] ), ext = "jpg" )

                        losses = project.get_channel_loss( i[ 0 ] )
                        gains  = project.get_channel_gain( i[ 0 ] )

                        btn = ChannelImageButton( size_hint = ( None, None ), size = ( image.texture.width, image.texture.height ) )
                        btn.__channel_id__ = i[ 0 ]
                        btn.texture = image.texture

                        height = image.texture.height
                        print( "height: %d" % height )

                        for i in losses:
                                print( "i.start_x: %d" % i[ 0 ] )
                                print( "i.end_x: %d" % i[ 1 ] )
                                with btn.canvas:
                                        Color( 1, 0, 0, 0.25 )
                                        d = 30
                                        Rectangle( pos = ( i[ 0 ], 0 ),
                                                   size = ( i[ 1 ] - i[ 0 ], height ) )

                        for i in gains:
                                with btn.canvas:
                                        Color( 0, 1, 0, 0.25 )
                                        d = 30
                                        Rectangle( pos = ( i[ 0 ], 0 ),
                                                   size = ( i[ 1 ] - i[ 0 ], height ) )

                        btn.canvas.ask_update( )
                        self.channel_scroll_view.button_list.add_widget( btn )
                        self.channel_scroll_view.button_list.width = image.texture.width
                        
kv file:

<ChannelScrollView>:
        button_list: button_list

        canvas.before:
                Color:
                        rgba: hex( "#646668" )
                Rectangle:
                        pos: self.pos
                        size: self.size

        GridLayout:
                canvas.before:
                        Color:
                                rgba: ( 1, 1, 1, 1 )
                        Rectangle:
                                pos: self.pos
                                size: self.size
                id: button_list
                size_hint_y: None
                size_hint_x: None
                spacing: 50
                cols: 1
                height: sum( x.height for x in self.children )