Линия между двумя перетаскиваемыми точками на холсте matplotlib pyqt5

Я пытаюсь провести линию между двумя перетаскиваемыми точками, которые находятся на холсте matplotlib, встроенным в приложение pyqt5. Я использую Draggable line с перетаскиваемыми точками в качестве ссылки. Однако я пытаюсь создать несколько строк, при этом создается одна из двух созданных объектов DraggablePoint. Для меня несколько проблем:

1. Строка появляется только тогда, когда точки перетаскиваются (решается, см. Обновление ниже)
2. Линия смещена на разность, которая, как я полагаю, является разницей между холстом и фактическим графиком matplotlib. Однако масштабирование не является правильным.
3. Линия для второй пары точек вообще не отображается

Ниже мой адаптированный код:

DraggablePoint

import matplotlib.pyplot as plt
import matplotlib.patches as patches
from matplotlib.lines import Line2D
import matplotlib


class DraggablePoint:



    lock = None 

    def __init__(self, parent, dominant, x=10, y=10, size=1):
        """Creates a draggable Point on a matplotlib canvas"""
        matplotlib.matplotlib_fname()
        # The FigureCanvas
        self.parent = parent
        # The Point
        self.point = patches.Ellipse((x, y), size, size, fc='r', alpha=0.5, edgecolor='r')
        #Coordinates of the point
        self.x = x
        self.y = y
        self.dy = 645
        self.dx = 263
        # Adds the point to the Plot
        parent.fig.axes[0].add_patch(self.point)
        # Used in the on_press() function
        self.press = None
        self.background = None
        # initiate the mpl_connects
        self.connect()
        # The Other DraggablePoint, with whom the line shall connect with.
        self.partner = None
        # The Line2D
        self.line = None
        # TODO
        self.dominant = dominant

        for pair in self.parent.point_pairs:
            if self in pair:
                if pair[1]:
                    line_x = [pair[0].x+self.dx, pair[1].x+self.dx]
                    line_y = [pair[0].y+self.dy, pair[1].y+self.dy]
                    self.line = Line2D(line_x, line_y, color='r', alpha=0.5)
                    parent.fig.axes[0].add_line(self.line)


    def connect(self):

        'connect to all the events we need'
        # print("LOG.INFO: DraggablePoint.connect")
        self.cidpress = self.point.figure.canvas.mpl_connect('button_press_event', self.on_press)
        self.cidrelease = self.point.figure.canvas.mpl_connect('button_release_event', self.on_release)
        self.cidmotion = self.point.figure.canvas.mpl_connect('motion_notify_event', self.on_motion)


    def on_press(self, event):
        '''Initiates when a Point is clicked on'''
        # print(self.partner)
        # print(event.xdata, event.ydata)
        if event.inaxes != self.point.axes: return
        if DraggablePoint.lock is not None: return
        contains, attrd = self.point.contains(event)
        if not contains: return
        self.press = (self.point.center), event.xdata, event.ydata
        DraggablePoint.lock = self


        # draw everything but the selected rectangle and store the pixel buffer
        canvas = self.point.figure.canvas
        axes = self.point.axes
        self.point.set_animated(True)
        for pair in self.parent.point_pairs:
            if self == pair[1]:
                self.line.set_animated(True)
            elif self == pair[0]:
                self.partner.line.set_animated(True)


        #TODO
        canvas.draw()
        self.background = canvas.copy_from_bbox(self.point.axes.bbox)

        # now redraw just the rectangle
        axes.draw_artist(self.point)

        # and blit just the redrawn area
        canvas.blit(axes.bbox)


    def on_motion(self, event):

        # print("LOG.INFO: DraggablePoint.on_motion")
        if DraggablePoint.lock is not self:
            return
        if event.inaxes != self.point.axes: return
        # print("LOG.INFO: DraggablePoint.on_motion.after_lock")
        # self.parent.updateFigure()
        self.point.center, xpress, ypress = self.press
        dx = event.xdata - xpress
        dy = event.ydata - ypress
        self.point.center = (self.point.center[0]+dx, self.point.center[1]+dy)


        canvas = self.point.figure.canvas
        axes = self.point.axes
        # restore the background region
        canvas.restore_region(self.background)

        # redraw just the current rectangle
        axes.draw_artist(self.point)

        for pair in self.parent.point_pairs:
            if self in pair:
                if self == pair[1]:
                    axes.draw_artist(self.line)
                else:
                    pair[1].line.set_animated(True)
                    axes.draw_artist(pair[1].line)



        self.x = self.point.center[0]
        self.y = self.point.center[1]

        for pair in self.parent.point_pairs:
            if self == pair[1]:
                line_x = [pair[0].x+self.dx, self.x+self.dx]
                line_y = [pair[0].y+self.dy, self.y+self.dy]
                self.line.set_data(line_x, line_y)
            elif self == pair[0]:
                line_x = [pair[1].x+self.dx, self.x+self.dx]
                line_y = [pair[1].y+self.dy, self.y+self.dy]
                pair[1].line.set_data(line_x, line_y)

        # blit just the redrawn area
        canvas.blit(axes.bbox)
        # print(self.line)


    def on_release(self, event):

        # print("LOG.INFO: DraggablePoint.on_release")
        'on release we reset the press data'
        if DraggablePoint.lock is not self:
            return

        # print("LOG.INFO: DraggablePoint.on_release.after_lock")
        self.press = None
        DraggablePoint.lock = None

        # turn off the rect animation property and reset the background
        self.point.set_animated(False)
        axes = self.point.axes

        for pair in self.parent.point_pairs:
            if self in pair:
                if pair[1] == self:
                    self.line.set_animated(False)
                else:
                    pair[1].line.set_animated(False)



        self.background = None

        # redraw the full figure
        self.point.figure.canvas.draw()

        self.x = self.point.center[0]
        self.y = self.point.center[1]
        print(self.line.__str__() + "RELEASE")

    def disconnect(self):

        'disconnect all the stored connection ids'

        self.point.figure.canvas.mpl_disconnect(self.cidpress)
        self.point.figure.canvas.mpl_disconnect(self.cidrelease)
        self.point.figure.canvas.mpl_disconnect(self.cidmotion)

    def setLine(self, line):
        self.line = line

Встраивание в графический интерфейс

class PlotCanvas(FigureCanvas):

    def __init__(self, parent=None, width=5, height=4, dpi=100):
        self.fig = Figure(figsize=(width, height), dpi=dpi)
        self.axes = self.fig.add_subplot(111)

        FigureCanvas.__init__(self, self.fig)
        self.setParent(parent)

        FigureCanvas.setSizePolicy(self,
                                   QSizePolicy.Expanding,
                                   QSizePolicy.Expanding)
        FigureCanvas.updateGeometry(self)
        self.xcoords = []
        self.ycoords = []
        self.lines = []
        self.list_points = []
        self.point_pairs = []
        self.number_of_lines = 0
        # self.mpl_connect('button_press_event', self.plot_draggable_point)
        self.plot_line = False
        self.plot()
        self.create_draggable_points()


    def plot(self):
        # data = [random.random() for i in range(25)]

        # self.a = plt.scatter(M[:, 0], M[:, 1])
        data = dataset2.get_matrix()
        ax = self.figure.add_subplot(111)
        ax.scatter(data[:, 0], data[:, 1], picker=10)
        ax.set_title('PyQt Matplotlib Example')
        self.draw()

    def create_draggable_points(self):
        self.list_points.append(DraggablePoint(self, True, 618.5047115210559, 338.5460575139148, 20))
        self.list_points.append(DraggablePoint(self, False, 338.5460575139148, 118.5047115210559, 20))
        # TODO Koordinaten an den Plot anpassen (+500)
        i = self.list_points[0]
        j = self.list_points[1]
        i.partner = j
        j.partner = i
        i.setLine(Line2D([i.x, j.x], [i.y, j.y], color='r', alpha=0.5))
        j.setLine(Line2D([i.x, j.x], [i.y, j.y], color='r', alpha=0.5))
        self.lines.append(i.line)
        self.lines.append(j.line)
        print(self.lines)

        self.point_pairs.append((i, j))

        self.updateFigure()


    def plot_draggable_point(self, event, size=60):
        if self.plot_line:
            self.xcoords.append(event.xdata)
            self.ycoords.append(event.ydata)
            print(event.xdata)
            print(event.ydata)
            self.list_points.append(DraggablePoint(self, event.xdata, event.ydata, size))
            if len(self.xcoords) == 2:
                self.list_points.append(DraggablePoint(self, event.xdata, event.ydata, size))
                self.xcoords[:] = []
                self.ycoords[:] = []
                self.list_points[:] = []
                self.plot_line = False
            self.updateFigure()

    def updateFigure(self):
        print(self.point_pairs)
        self.draw()

Класс называется так:

    layout = QGridLayout()
    self.m = PlotCanvas(self, width=10, height=8)
    layout.addWidget(self.m, 0, 0, 5, 1)

Обновить:

Первая проблема решена, я забыл перерисовать линию в on_release(). Теперь он выглядит так:

def on_release(self, event):

    'on release we reset the press data'
    if DraggablePoint.lock is not self:
        return

    self.press = None
    DraggablePoint.lock = None

    # turn off the rect animation property and reset the background
    self.point.set_animated(False)
    axes = self.point.axes

    for pair in self.parent.point_pairs:
        if self in pair:
            if pair[1] == self:
                self.line.set_animated(False)
            else:
                pair[1].line.set_animated(False)



    self.background = None

    # redraw the full figure
    self.point.figure.canvas.draw()

    self.x = self.point.center[0]
    self.y = self.point.center[1]


    for pair in self.parent.point_pairs:
        if self in pair:
            if pair[1] == self:
                axes.draw_artist(self.line)
            else:
                axes.draw_artist(pair[1].line)