Restricting panning range in matplotlib plots

Question

Is there any way to restrict the range that a user can interactively pan a plot in matplotlib?
For example, I'd like to limit the user's panning range to the positive quadrant of the plot, so x > 0 and y > 0, effectively creating floors at x = 0 and y = 0.

Answer 1

There is not built-in way to restrict zooming or panning other than restricting it to either the x or y direction. So you need to implement that yourself.

Connecting to the 'xlim_changed' and 'ylim_changed' events, you may check if the limits are valid or not, and potentially reset them to the valid range.

import matplotlib.pyplot as plt
import numpy as np


fig,ax=plt.subplots()

x = np.sin(np.linspace(0,10, 266))+1
ax.plot(x)

class Restrictor():
    def __init__(self, ax, x=lambda x: True,y=lambda x: True):
        self.res = [x,y]
        self.ax =ax
        self.limits = self.get_lim()
        self.ax.callbacks.connect('xlim_changed', lambda evt: self.lims_change(axis=0))
        self.ax.callbacks.connect('ylim_changed', lambda evt: self.lims_change(axis=1))

    def get_lim(self):
        return [self.ax.get_xlim(), self.ax.get_ylim()]

    def set_lim(self, axis, lim):
        if axis==0:
            self.ax.set_xlim(lim)
        else:
            self.ax.set_ylim(lim)
        self.limits[axis] = self.get_lim()[axis]

    def lims_change(self, event=None, axis=0):
        curlim = np.array(self.get_lim()[axis])
        if self.limits[axis] != self.get_lim()[axis]:
            # avoid recursion
            if not np.all(self.res[axis](curlim)):
                # if limits are invalid, reset them to previous state
                self.set_lim(axis, self.limits[axis])
            else:
                # if limits are valid, update previous stored limits
                self.limits[axis] = self.get_lim()[axis]

res = Restrictor(ax, x=lambda x: x>=0,y=lambda x: x>=0)

plt.show()

The user experience of such limitations are not great, since a certain action (like moving the mouse) is not answered with the expected behaviour (plot does not move); but one has to judge for oneself if this would still make sense.