"""
.. _line_widget_example:

Line Widget
~~~~~~~~~~~

The line widget can be enabled and disabled by the
:func:`pyvista.Plotter.add_line_widget` and
:func:`pyvista.Plotter.clear_line_widgets` methods respectively.
Unfortunately, PyVista does not have any helper methods to utilize this
widget, so it is necessary to pass a custom callback method.

One particularly fun example is to use the line widget to create a source for
the :func:`pyvista.DataSetFilters.streamlines` filter. Again note the use of
the ``name`` argument in ``add_mesh``.
"""

# sphinx_gallery_start_ignore
# widgets do not work in interactive examples
PYVISTA_GALLERY_FORCE_STATIC_IN_DOCUMENT = True
# sphinx_gallery_end_ignore

import numpy as np
import pyvista as pv
from pyvista import examples

pv.set_plot_theme('document')

mesh = examples.download_kitchen()
furniture = examples.download_kitchen(split=True)

arr = np.linalg.norm(mesh['velocity'], axis=1)
clim = [arr.min(), arr.max()]

# %%

pl = pv.Plotter()
pl.add_mesh(furniture, name='furniture', color=True)
pl.add_mesh(mesh.outline(), color='black')
pl.add_axes()


def simulate(pointa, pointb):
    streamlines = mesh.streamlines(
        n_points=10,
        max_steps=100,
        pointa=pointa,
        pointb=pointb,
        integration_direction='forward',
    )
    pl.add_mesh(
        streamlines,
        name='streamlines',
        line_width=5,
        render_lines_as_tubes=True,
        clim=clim,
    )


pl.add_line_widget(callback=simulate, use_vertices=True)
pl.show()

# %%
# And here is a screen capture of a user interacting with this
#
# .. image:: ../../images/gifs/line-widget-streamlines.gif
#
# %%
# .. tags:: widgets
