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"""
===========
Path editor
===========
Sharing events across GUIs.
This example demonstrates a cross-GUI application using Matplotlib event
handling to interact with and modify objects on the canvas.
.. note::
This example exercises the interactive capabilities of Matplotlib, and this
will not appear in the static documentation. Please run this code on your
machine to see the interactivity.
You can copy and paste individual parts, or download the entire example
using the link at the bottom of the page.
"""
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.backend_bases import MouseButton
from matplotlib.patches import PathPatch
from matplotlib.path import Path
fig, ax = plt.subplots()
pathdata = [
(Path.MOVETO, (1.58, -2.57)),
(Path.CURVE4, (0.35, -1.1)),
(Path.CURVE4, (-1.75, 2.0)),
(Path.CURVE4, (0.375, 2.0)),
(Path.LINETO, (0.85, 1.15)),
(Path.CURVE4, (2.2, 3.2)),
(Path.CURVE4, (3, 0.05)),
(Path.CURVE4, (2.0, -0.5)),
(Path.CLOSEPOLY, (1.58, -2.57)),
]
codes, verts = zip(*pathdata)
path = Path(verts, codes)
patch = PathPatch(
path, facecolor='green', edgecolor='yellow', alpha=0.5)
ax.add_patch(patch)
class PathInteractor:
"""
A path editor.
Press 't' to toggle vertex markers on and off. When vertex markers are on,
they can be dragged with the mouse.
"""
showverts = True
epsilon = 5 # max pixel distance to count as a vertex hit
def __init__(self, pathpatch):
self.ax = pathpatch.axes
canvas = self.ax.figure.canvas
self.pathpatch = pathpatch
self.pathpatch.set_animated(True)
x, y = zip(*self.pathpatch.get_path().vertices)
self.line, = ax.plot(
x, y, marker='o', markerfacecolor='r', animated=True)
self._ind = None # the active vertex
canvas.mpl_connect('draw_event', self.on_draw)
canvas.mpl_connect('button_press_event', self.on_button_press)
canvas.mpl_connect('key_press_event', self.on_key_press)
canvas.mpl_connect('button_release_event', self.on_button_release)
canvas.mpl_connect('motion_notify_event', self.on_mouse_move)
self.canvas = canvas
def get_ind_under_point(self, event):
"""
Return the index of the point closest to the event position or *None*
if no point is within ``self.epsilon`` to the event position.
"""
xy = self.pathpatch.get_path().vertices
xyt = self.pathpatch.get_transform().transform(xy) # to display coords
xt, yt = xyt[:, 0], xyt[:, 1]
d = np.sqrt((xt - event.x)**2 + (yt - event.y)**2)
ind = d.argmin()
return ind if d[ind] < self.epsilon else None
def on_draw(self, event):
"""Callback for draws."""
self.background = self.canvas.copy_from_bbox(self.ax.bbox)
self.ax.draw_artist(self.pathpatch)
self.ax.draw_artist(self.line)
def on_button_press(self, event):
"""Callback for mouse button presses."""
if (event.inaxes is None
or event.button != MouseButton.LEFT
or not self.showverts):
return
self._ind = self.get_ind_under_point(event)
def on_button_release(self, event):
"""Callback for mouse button releases."""
if (event.button != MouseButton.LEFT
or not self.showverts):
return
self._ind = None
def on_key_press(self, event):
"""Callback for key presses."""
if not event.inaxes:
return
if event.key == 't':
self.showverts = not self.showverts
self.line.set_visible(self.showverts)
if not self.showverts:
self._ind = None
self.canvas.draw()
def on_mouse_move(self, event):
"""Callback for mouse movements."""
if (self._ind is None
or event.inaxes is None
or event.button != MouseButton.LEFT
or not self.showverts):
return
vertices = self.pathpatch.get_path().vertices
vertices[self._ind] = event.xdata, event.ydata
self.line.set_data(zip(*vertices))
self.canvas.restore_region(self.background)
self.ax.draw_artist(self.pathpatch)
self.ax.draw_artist(self.line)
self.canvas.blit(self.ax.bbox)
interactor = PathInteractor(patch)
ax.set_title('drag vertices to update path')
ax.set_xlim(-3, 4)
ax.set_ylim(-3, 4)
plt.show()
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