Viewport with fixed resolution autofit to window

Summary

• author: hansent
• kivy: >= 1.2

I use this viewport widget as the root widget in many apps that have a fixed resolution. The viewport will automatically fit itself to the window after its been created (including rotating if its a better fit). This makes testing apps for large resolution like 1080p on smaller screens a lot easier.

Usage

#!python

from kivy.app import App
from kivy.factory import Factory
from viewport import Viewport

class ViewportApp(App):
    def build(self):
        self.root = Viewport(size=(1080,1920))
        self.root.add_widget(Factory.Button(text="ViewportApp"))
        return self.root

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

Files

viewport.py

#!python
from kivy.clock import Clock
from kivy.core.window import Window
from kivy.uix.scatter import ScatterPlane


class Viewport(ScatterPlane):
    def __init__(self, **kwargs):
        kwargs.setdefault('size', (1920, 1080))
        kwargs.setdefault('size_hint', (None, None))
        kwargs.setdefault('do_scale', False)
        kwargs.setdefault('do_translation', False)
        kwargs.setdefault('do_rotation', False)
        super(Viewport, self).__init__( **kwargs)
        Window.bind(system_size=self.on_window_resize)
        Clock.schedule_once(self.fit_to_window, -1)

    def on_window_resize(self, window, size):
        self.fit_to_window()

    def fit_to_window(self, *args):
        if self.width < self.height: #portrait
            if Window.width < Window.height: #so is window   
                self.scale = Window.width/float(self.width)
            else: #window is landscape..so rotate vieport
                self.scale = Window.height/float(self.width)
                self.rotation = -90
        else: #landscape
            if Window.width > Window.height: #so is window   
                self.scale = Window.width/float(self.width)
            else: #window is portrait..so rotate vieport
                self.scale = Window.height/float(self.width)
                self.rotation = -90

        self.center = Window.center
        for c in self.children:
            c.size = self.size

    def add_widget(self, w, *args, **kwargs):
        super(Viewport, self).add_widget(w, *args, **kwargs)
        w.size = self.size

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