Appending data with napari threads

appending_data.py

"""
This script is adapted from https://github.com/napari/napari/blob/master/examples/interactive_scripting.py

Instead of replacing the entire layer data, we want to append to the data stack.
However it produces "WARNING: Cannot make QOpenGLContext current in a different thread"
"""
import numpy as np
import napari
from napari.qt import thread_worker
import time


with napari.gui_qt():
    # create the viewer with an image
    data = np.random.random((1, 512, 512))
    viewer = napari.Viewer()
    layer = viewer.add_image(data)

    @thread_worker(start_thread=True)
    def layer_update(*, update_period, num_updates):
        # number of times to update
        for k in range(num_updates):
            time.sleep(update_period)

            dat = np.random.random((1, 512, 512))
            layer.data = np.concatenate((dat, layer.data), axis=0)

            # check that data layer is properly assigned and not blocked?
            while layer.data.all() != dat.all():
                layer.data = dat
            yield

    layer_update(update_period=0.05, num_updates=100)