#!/usr/bin/env python3

import nanogui
from nanogui import glfw
from nanogui import BoxLayout, Button, Label, Orientation, Screen, Window


class HelloWorldApp(Screen):
    def __init__(self, size=(400, 300)):
        super().__init__(size, "NanoGUI Hello World")
        self.win = Window(self, "Demo Window")

        self.win.set_layout(BoxLayout(Orientation.Vertical, margin=20, spacing=20))
        self.resize_event(size)

        Label(self.win, "NanoGUI Demo", "sans-bold")
        b = Button(self.win, "Say hello!")

        def cb():
            print("Well, 'ello there!")

        b.set_callback(cb)

        self.set_visible(True)
        self.perform_layout()

    def resize_event(self, size):
        self.win.set_fixed_size(size)
        self.win.set_size(size)
        self.win.center()
        self.win.perform_layout(self.nvg_context())
        super().resize_event(size)
        return True

    def keyboard_event(self, key, scancode, action, modifiers):
        if super().keyboard_event(key, scancode, action, modifiers):
            return True

        if key == glfw.KEY_ESCAPE and action == glfw.PRESS:
            self.set_visible(False)
            return True

        return False


if __name__ == "__main__":
    import gc

    nanogui.init()
    app = HelloWorldApp()
    nanogui.mainloop(refresh=1 / 60.0 * 1000)
    del app
    gc.collect()
    nanogui.shutdown()