Show a textured quad

import numpy as np

from vispy import gloo, app
from vispy.gloo import Program

vertex = """
    attribute vec2 position;
    attribute vec2 texcoord;
    varying vec2 v_texcoord;
    void main()
    {
        gl_Position = vec4(position, 0.0, 1.0);
        v_texcoord = texcoord;
    } """

fragment = """
    uniform sampler2D texture;
    varying vec2 v_texcoord;
    void main()
    {
        gl_FragColor = texture2D(texture, v_texcoord);
    } """


def checkerboard(grid_num=8, grid_size=32):
    row_even = grid_num // 2 * [0, 1]
    row_odd = grid_num // 2 * [1, 0]
    Z = np.row_stack(grid_num // 2 * (row_even, row_odd)).astype(np.uint8)
    return 255 * Z.repeat(grid_size, axis=0).repeat(grid_size, axis=1)


class Canvas(app.Canvas):
    def __init__(self):
        app.Canvas.__init__(self, size=(512, 512), title='Textured quad',
                            keys='interactive')

        # Build program & data
        self.program = Program(vertex, fragment, count=4)
        self.program['position'] = [(-1, -1), (-1, +1),
                                    (+1, -1), (+1, +1)]
        self.program['texcoord'] = [(0, 0), (1, 0), (0, 1), (1, 1)]
        self.program['texture'] = checkerboard()

        gloo.set_viewport(0, 0, *self.physical_size)

        self.show()

    def on_draw(self, event):
        gloo.set_clear_color('white')
        gloo.clear(color=True)
        self.program.draw('triangle_strip')

    def on_resize(self, event):
        gloo.set_viewport(0, 0, *event.physical_size)

if __name__ == '__main__':
    c = Canvas()
    app.run()