Cannot hide widget in box layout

[M Dammer]

My application consists of an image with a widget bar to the left and to the right. I want to be able to hide these bars when a toggle button is pressed.

I have created a callback that toggles the size_hint_x property of both bars (BoxLayouts). While the right bar disappears and the image stretches to the right as they should, the left bar stays untouched (see second image at the bottom).

Here are the KV and Python files:

<MyScreen>:

    image_wid: my_image

    osd_wid: my_osd

    lpan_wid: my_lpan

    rpan_wid: my_rpan

    BoxLayout:

        orientation: 'vertical'

        BoxLayout:

            BoxLayout:

                id: my_lpan

                size_hint_x: 0.1

                Button:

                    text: 'left'

            Image:

                id: my_image

                source: '1.png'

                allow_stretch: True

            BoxLayout:

                id: my_rpan

                size_hint_x: 0.1

                Button:

                    text: 'right'

        BoxLayout:

            size_hint_y: 0.1

            ToggleButton:

                id: my_osd

                state: 'down'

                text: 'Show / Hide bars'

#!/usr/bin/env python

from kivy.app import App

from kivy.uix.widget import Widget

from kivy.uix.boxlayout import BoxLayout

from kivy.uix.image import Image

from kivy.uix.togglebutton import ToggleButton

from kivy.properties import ObjectProperty

class MyScreen(BoxLayout):

    osd_wid = ObjectProperty()

    lpan_wid = ObjectProperty()

    rpan_wid = ObjectProperty()

class BartestApp(App):

    def osd_callback(self, instance, value):

        if value == 'normal':

            self.rootwidget.lpan_wid.size_hint_x = 0

            self.rootwidget.rpan_wid.size_hint_x = 0

        else:

            self.rootwidget.lpan_wid.size_hint_x = 0.1

            self.rootwidget.rpan_wid.size_hint_x = 0.1

    def build(self):

        self.rootwidget = MyScreen()

        self.rootwidget.osd_wid.bind(state=self.osd_callback)

        return self.rootwidget

if __name__ == '__main__':

    BartestApp().run()

[ZenCODE]

That does seem like a bug. I've played around a bit but the button always has a width, even when you disable the lpan and rpan size hints and manually set the widths to 0.

Please log an issue posting you code with it.

In the meantime, you can achieve the same using a floatlayout (moving them off screen) or setting their opacity to 0 and disabling the button?

Thanks

[M Dammer]

Thanks for your help!

I could achieve a partial solution of the problem by using a GridLayout with three columns as the Parent, but this brought up the problem that when I set size_hint_x = 0 for the sidebars they are only almost disappearing, but there is always a bit of widget left.

I think a generic boolean property that allows to completely make a widget non-existent in the UI and that makes all these kludges history is overdue in Kivy.

[ZenCODE]

That is predicable based on the BoxLayout behavior. I really suggest using a FloatLayout and just moving them off-screen. One benefit of this approach is that you can animate using the Animation object. So they can slide out, in a fluid and sexy way.

That's one of the benefits of Kivy's novel interface. It's can be more that just a Material design/iOS interface guideline. It can be beautiful and interactive :-)

[ZenCODE]

ps. If you're unclear on how to do this, please ask and I will post an example....

[M Dammer]

Thanks, I Have done this now and everything works as expected.