在 pyqt5 中包含带有悬停标签的 matplotlib

Posted 2023-03-30

【中文标题】在 pyqt5 中包含带有悬停标签的 matplotlib

【英文标题】：Include matplotlib in pyqt5 with hover labels

【发布时间】：2017-06-23 16:40:09

【问题描述】：

我有一个来自 matplotlib 的图，我想在鼠标悬停时在标记点上显示标签。

我在 SO 上找到了this very helpful working example，我试图将完全相同的图集成到 pyqt5 应用程序中。 不幸的是，当在应用程序中有绘图时，悬停不再起作用。

这是基于上述 SO 帖子的完整工作示例：

import matplotlib.pyplot as plt
import scipy.spatial as spatial
import numpy as np
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
import sys

pi = np.pi
cos = np.cos


def fmt(x, y):
    return 'x: x:0.2f\ny: y:0.2f'.format(x=x, y=y)

class FollowDotCursor(object):
    """Display the x,y location of the nearest data point.
    https://***.com/a/4674445/190597 (Joe Kington)
    https://***.com/a/13306887/190597 (unutbu)
    https://***.com/a/15454427/190597 (unutbu)
    """
    def __init__(self, ax, x, y, tolerance=5, formatter=fmt, offsets=(-20, 20)):
        try:
            x = np.asarray(x, dtype='float')
        except (TypeError, ValueError):
            x = np.asarray(mdates.date2num(x), dtype='float')
        y = np.asarray(y, dtype='float')
        mask = ~(np.isnan(x) | np.isnan(y))
        x = x[mask]
        y = y[mask]
        self._points = np.column_stack((x, y))
        self.offsets = offsets
        y = y[np.abs(y-y.mean()) <= 3*y.std()]
        self.scale = x.ptp()
        self.scale = y.ptp() / self.scale if self.scale else 1
        self.tree = spatial.cKDTree(self.scaled(self._points))
        self.formatter = formatter
        self.tolerance = tolerance
        self.ax = ax
        self.fig = ax.figure
        self.ax.xaxis.set_label_position('top')
        self.dot = ax.scatter(
            [x.min()], [y.min()], s=130, color='green', alpha=0.7)
        self.annotation = self.setup_annotation()
        plt.connect('motion_notify_event', self)

    def scaled(self, points):
        points = np.asarray(points)
        return points * (self.scale, 1)

    def __call__(self, event):
        ax = self.ax
        # event.inaxes is always the current axis. If you use twinx, ax could be
        # a different axis.
        if event.inaxes == ax:
            x, y = event.xdata, event.ydata
        elif event.inaxes is None:
            return
        else:
            inv = ax.transData.inverted()
            x, y = inv.transform([(event.x, event.y)]).ravel()
        annotation = self.annotation
        x, y = self.snap(x, y)
        annotation.xy = x, y
        annotation.set_text(self.formatter(x, y))
        self.dot.set_offsets((x, y))
        bbox = ax.viewLim
        event.canvas.draw()

    def setup_annotation(self):
        """Draw and hide the annotation box."""
        annotation = self.ax.annotate(
            '', xy=(0, 0), ha = 'right',
            xytext = self.offsets, textcoords = 'offset points', va = 'bottom',
            bbox = dict(
                boxstyle='round,pad=0.5', fc='yellow', alpha=0.75),
            arrowprops = dict(
                arrowstyle='->', connectionstyle='arc3,rad=0'))
        return annotation

    def snap(self, x, y):
        """Return the value in self.tree closest to x, y."""
        dist, idx = self.tree.query(self.scaled((x, y)), k=1, p=1)
        try:
            return self._points[idx]
        except IndexError:
            # IndexError: index out of bounds
            return self._points[0]


class MainWindow(QMainWindow):

    def __init__(self):
        super().__init__()

        self.width = 1000
        self.height = 800
        self.setGeometry(0, 0, self.width, self.height)

        canvas = self.get_canvas()

        w = QWidget()
        w.layout = QHBoxLayout()
        w.layout.addWidget(canvas)
        w.setLayout(w.layout)

        self.setCentralWidget(w)

        self.show()


    def get_canvas(self):
        fig, ax = plt.subplots()
        x = np.linspace(0.1, 2*pi, 10)
        y = cos(x)
        markerline, stemlines, baseline = ax.stem(x, y, '-.')
        plt.setp(markerline, 'markerfacecolor', 'b')
        plt.setp(baseline, 'color','r', 'linewidth', 2)
        cursor = FollowDotCursor(ax, x, y, tolerance=20)

        canvas = FigureCanvas(fig)

        return canvas


app = QApplication(sys.argv)
win = MainWindow()
sys.exit(app.exec_())

当鼠标悬停在 pyqt 应用程序中时，我需要做什么才能使标签也显示？

【参考方案1】：

第一个问题可能是您没有保留对 FollowDotCursor 的引用。

所以要确保FollowDotCursor 保持活动状态，您可以将其设为类变量

self.cursor = FollowDotCursor(ax, x, y, tolerance=20)

而不是cursor = ...。

接下来，确保在 为图形提供画布之后实例化 Cursor 类。

canvas = FigureCanvas(fig)
self.cursor = FollowDotCursor(ax, x, y, tolerance=20)

最后，在 FollowDotCursor 中保留对回调的引用，不要使用 plt.connect，而是使用画布本身：

self.cid = self.fig.canvas.mpl_connect('motion_notify_event', self)