{
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n# Looking glass\n\nExample using mouse events to simulate a looking glass for inspecting data.\n\n<div class=\"alert alert-info\"><h4>Note</h4><p>This example exercises the interactive capabilities of Matplotlib, and this\n    will not appear in the static documentation. Please run this code on your\n    machine to see the interactivity.\n\n    You can copy and paste individual parts, or download the entire example\n    using the link at the bottom of the page.</p></div>\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "import matplotlib.pyplot as plt\nimport numpy as np\n\nimport matplotlib.patches as patches\n\n# Fixing random state for reproducibility\nnp.random.seed(19680801)\n\nx, y = np.random.rand(2, 200)\n\nfig, ax = plt.subplots()\ncirc = patches.Circle((0.5, 0.5), 0.25, alpha=0.8, fc='yellow')\nax.add_patch(circ)\n\n\nax.plot(x, y, alpha=0.2)\nline, = ax.plot(x, y, alpha=1.0, clip_path=circ)\nax.set_title(\"Left click and drag to move looking glass\")\n\n\nclass EventHandler:\n    def __init__(self):\n        fig.canvas.mpl_connect('button_press_event', self.on_press)\n        fig.canvas.mpl_connect('button_release_event', self.on_release)\n        fig.canvas.mpl_connect('motion_notify_event', self.on_move)\n        self.x0, self.y0 = circ.center\n        self.pressevent = None\n\n    def on_press(self, event):\n        if event.inaxes != ax:\n            return\n\n        if not circ.contains(event)[0]:\n            return\n\n        self.pressevent = event\n\n    def on_release(self, event):\n        self.pressevent = None\n        self.x0, self.y0 = circ.center\n\n    def on_move(self, event):\n        if self.pressevent is None or event.inaxes != self.pressevent.inaxes:\n            return\n\n        dx = event.xdata - self.pressevent.xdata\n        dy = event.ydata - self.pressevent.ydata\n        circ.center = self.x0 + dx, self.y0 + dy\n        line.set_clip_path(circ)\n        fig.canvas.draw()\n\nhandler = EventHandler()\nplt.show()"
      ]
    }
  ],
  "metadata": {
    "kernelspec": {
      "display_name": "Python 3",
      "language": "python",
      "name": "python3"
    },
    "language_info": {
      "codemirror_mode": {
        "name": "ipython",
        "version": 3
      },
      "file_extension": ".py",
      "mimetype": "text/x-python",
      "name": "python",
      "nbconvert_exporter": "python",
      "pygments_lexer": "ipython3",
      "version": "3.14.6"
    }
  },
  "nbformat": 4,
  "nbformat_minor": 0
}