.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "_gallery/feature_demo/text_waterfall.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download__gallery_feature_demo_text_waterfall.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr__gallery_feature_demo_text_waterfall.py:


Text waterfall
==============

An example showing a waterfall of text. On the left it shows the
contents of the glyph atlas. One goal of this example is to strain the
text rendering to its limits.

.. GENERATED FROM PYTHON SOURCE LINES 9-105



.. image-sg:: /_gallery/feature_demo/images/sphx_glr_text_waterfall_001.webp
   :alt: text waterfall
   :srcset: /_gallery/feature_demo/images/sphx_glr_text_waterfall_001.webp
   :class: sphx-glr-single-img





.. code-block:: Python



    from rendercanvas.auto import RenderCanvas, loop
    import pygfx as gfx
    import numpy as np


    renderer = gfx.renderers.WgpuRenderer(RenderCanvas(size=(800, 400)))
    scene = gfx.Scene()
    glyph_atlas = gfx.utils.text.glyph_atlas
    glyph_atlas.clear_free_regions = True  # So we can see regions being freed

    # Add background
    background = gfx.Background.from_color("#dde", "#fff")
    scene.add(background)

    # Add an image that shows the glyph atlas
    atlas_viewer = gfx.Mesh(
        gfx.plane_geometry(100, 100),
        gfx.MeshBasicMaterial(color="red"),
    )
    scene.add(atlas_viewer)
    atlas_viewer.local.x = -50

    camera = gfx.OrthographicCamera(200, 100)

    # Create a bunch of reusable text objects


    def character_generator():
        pieces = gfx.font_manager.select_font(" ", gfx.font_manager.default_font_props)
        font = pieces[0][1]
        while True:
            for c in font.codepoints:
                yield chr(c)


    chargen = character_generator()

    live_objects = set()
    waiting_objects = set()

    text_material = gfx.TextMaterial(color="#06E")

    for _i in range(100):
        obj = gfx.Text(text=" ", font_size=18, screen_space=True, material=text_material)
        scene.add(obj)
        waiting_objects.add(obj)
        obj.local.y = -999


    # The animate function makes the text objects fall down, and update the objects
    # with a new character once they start their fall again.
    # Until we have real garbage collection for glyphs, we fake it here.


    def animate():
        garbage_collect = True

        # Let them fall
        for obj in list(live_objects):
            obj.local.y -= obj.fall_speed
            if obj.local.y < -60:
                live_objects.discard(obj)
                waiting_objects.add(obj)
                if garbage_collect:
                    all_indices = set()
                    for x in live_objects:
                        atlas_indices = x.geometry.glyph_data.data["atlas_index"]
                        all_indices.update(int(index) for index in atlas_indices)
                    for index in obj.geometry.glyph_data.data["atlas_index"]:
                        index = int(index)
                        if index not in all_indices:
                            glyph_atlas.free_region(index)

        # Drop new objects
        if waiting_objects:
            obj = waiting_objects.pop()
            live_objects.add(obj)
            obj.local.y = 50
            obj.local.x = np.random.uniform(0, 100)
            obj.set_text(next(chargen))
            obj.fall_speed = np.random.uniform(1, 4)

        # Update the image
        if atlas_viewer.material.map is not glyph_atlas.texture:
            atlas_viewer.material.map = glyph_atlas.texture

        # Render
        renderer.render(scene, camera)
        renderer.request_draw()


    if __name__ == "__main__":
        renderer.request_draw(animate)
        loop.run()


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 16.334 seconds)


.. _sphx_glr_download__gallery_feature_demo_text_waterfall.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: text_waterfall.ipynb <text_waterfall.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: text_waterfall.py <text_waterfall.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: text_waterfall.zip <text_waterfall.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_

.. only:: html

    Interactive example
    -------------------

    Try this example in your browser using Pyodide. Might not work with all examples and all devices. Check the output and your browser's console for details.

    .. raw:: html

        <iframe src="./../pyodide.html#text_waterfall.py"></iframe>