Change default key -- 'P' -- for picking under the mouse to other key

[AlexanderG77]

How to change the default 'P' key for picking a point on the surface of a mesh, using pyvista.Plotter.enable_surface_point_picking(), to any other key(s)?
I am aware about binding a callback function to a key event with pyvista.Plotter.add_key_event(), but I can not figure out what function is called when pressing 'P' after pyvista.Plotter.enable_surface_point_picking().

[banesullivan]

That P key comes directly from the VTK interaction style and isn't easy to change. However, you can add additional keys to trigger the pick event by borrowing some of our internal implementations:

pyvista/pyvista/plotting/picking.py

Lines 30 to 37 in d72ba08

	def _launch_pick_event(interactor, event):
	"""Create a Pick event based on coordinate or left-click."""
	click_x, click_y = interactor.GetEventPosition()
	click_z = 0
	picker = interactor.GetPicker()
	renderer = interactor.GetInteractorStyle()._parent()._plotter.iren.get_poked_renderer()
	picker.Pick(click_x, click_y, click_z, renderer)

pyvista/pyvista/plotting/picking.py

Lines 321 to 331 in d72ba08

	def _init_click_picking_callback(self, left_clicking=False):
	if left_clicking:
	self._picking_left_clicking_observer = self.iren.add_observer(
	"LeftButtonPressEvent",
	partial(try_callback, _launch_pick_event),
	)
	else:
	self._picking_right_clicking_observer = self.iren.add_observer(
	"RightButtonPressEvent",
	partial(try_callback, _launch_pick_event),
	)

pyvista/pyvista/plotting/picking.py

Lines 306 to 319 in d72ba08

	def pick_mouse_position(self):
	"""Get corresponding mouse location in the 3D plot.
	Returns
	-------
	tuple
	Three item tuple with the 3D picked position.
	"""
	if self.mouse_position is None:
	self.store_mouse_position()
	renderer = self.iren.get_poked_renderer()
	self.iren.picker.Pick(self.mouse_position[0], self.mouse_position[1], 0, renderer)
	return self.iren.picker.GetPickPosition()

Here's one example:

import pyvista as pv
pl = pv.Plotter(notebook=False)
pl.add_mesh(pv.Sphere())
pl.enable_point_picking()
pl.track_mouse_position()  # continous mouse position tracking (can have performance implications)
pl.add_key_event("t", pl.pick_mouse_position)
pl.show()