Understanding difference between self.x, self.width and root.width

[Shoumik Das]

Hi. I have built a simple screen to understand the concepts behind self.x, self.width and root.width. My intention is to place a text label at the center of my app screen. This is my kv file:

This one works fine.

<SivaTabbedScreen>:
    name: 'tabbed_screen'
    FloatLayout:
        size: root.width, root.height
        Label:
            pos: self.x*0.5, self.y*0.5
            text: 'SECOND SCREEN'
            font_size: '50sp'

This one does not work as intended.

<SivaTabbedScreen>:
    name: 'tabbed_screen'
    FloatLayout:
        size: root.width, root.height
        Label:
            pos: self.width*0.5, self.height*0.5
            text: 'SECOND SCREEN'
            font_size: '50sp'

Can you please help me understand the different values of self.x, self.width and root.width in the above examples?

[Elliot Garbus]

Read about x, y height and width in: https://kivy.org/doc/stable/api-kivy.uix.widget.html?highlight=widget#module-kivy.uix.widget

 

In short:

self.x and self.y are the position of the lower left corner of the widget.

self.height and self.width are the height and width of the widget.

 

Read about root: https://kivy.org/doc/stable/api-kivy.lang.html?highlight=lang#value-expressions-on-property-expressions-ids-and-reserved-keywords

root.width is the width of the SivaTabbedScreen.

 

You can print root, print(root) or print(self) to see what it is.

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[Shoumik Das]

Thank you for helping me understand.

[Elliot Garbus]

😊

 

From: Shoumik Das
Sent: Wednesday, April 29, 2020 8:40 AM
To: Kivy users support

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