如何在PyQtGraph中与圆表面交互？

Question

I have a circle that has been rendered using PyQtGraph. Inside the circle another graph is rendered. The graph consists of nodes and edges as usual. Currently, I can click on the nodes though and get their coordinates and do some calculations. But at the same time, if I click anywhere on the hollow surface of the circle it does not invoke any event. My requirement is to get the click point anywhere inside the circle. Below you can find the code to render my unit radius circle (considering the center of circle to be the origin) and the custom class.

import pyqtgraph as pg
import numpy as np
import math
from pyqtgraph.Qt import QtCore, QtGui

class Graph(pg.GraphItem):
    def __init__(self):
        self.dragPoint = None
        self.dragOffset = None
        self.textItems = []
        pg.GraphItem.__init__(self)
        self.scatter.sigClicked.connect(self.onclick)
        self.data = lambda x: None
        self.text = lambda x: None

    def setData(self, **kwds):
        self.text = kwds.pop('text', [])
        self.data = kwds
        if 'pos' in self.data:            
            npts = self.data['pos'].shape[0]
            self.data['data'] = np.empty(npts, dtype=[('index', int)])
            self.data['data']['index'] = np.arange(npts)
        self.settexts(self.text)
        self.updategraph()

    def settexts(self, text):
        for i in self.textItems:
            i.scene().removeItem(i)
        self.textItems = []
        for t in text:
            item = pg.TextItem(t)
            self.textItems.append(item)
            item.setParentItem(self)

    def updategraph(self):
        pg.GraphItem.setData(self, **self.data)
        for i, item in enumerate(self.textItems):
            item.setPos(*self.data['pos'][i])

    def mouseDragEvent(self, ev):
        if ev.button() != QtCore.Qt.LeftButton:
            ev.ignore()
            return

        if ev.isStart():
            # We are already one step into the drag.
            # Find the point(s) at the mouse cursor when the button was first
            # pressed:
            pos = ev.buttonDownPos()
            pts = self.scatter.pointsAt(pos)
            if len(pts) == 0:
                ev.ignore()
                return
            self.dragPoint = pts[0]
            ind = pts[0].data()[0]
            self.dragOffset = self.data['pos'][ind] - pos
        elif ev.isFinish():
            self.dragPoint = None
            return
        else:
            if self.dragPoint is None:
                ev.ignore()
                return

        ind = self.dragPoint.data()[0]
        self.data['pos'][ind] = ev.pos() + self.dragOffset
        self.updategraph()
        ev.accept()

    # Once a node on the graph is clicked, the clicked node should become the center of the graph
    def onclick(plot, points):
        x = 0
        y = 0
        x, y = points.ptsClicked[0]._data[0], points.ptsClicked[0]._data[1]     # position of the clicked point
        print('Clicked point is (' + str(x) + ', ' + str(y) + ')')


# Construct a unit radius circle for the graph
def plot_poincare_disc(graph_item_1, graph_item_2):
    # Two semicircles have been produced first and then joined later
    # As PyQtGraph needs a position matrix along with an adjacency matrix, hence pos and adj arrays

    # Semi-Circle 1
    pos1 = []
    adj1 = []
    length = 0
    # calculating y coordinates for 1000 evenly spaced points in (-1,1)
    for x in np.linspace(-1, 1, 1000):
        y = math.sqrt(1 - x ** 2)
        pos1.append([x, y])
        if len(pos1) > 1:
            adj1.append([length - 1, length])
        length = length + 1

    pos1 = np.array(pos1)
    adj1 = np.array(adj1)
    graph_item_1.setData(pos=pos1, adj=adj1, size=0.07)

    # Semi-circle 2
    pos2 = []
    adj2 = []
    length = 0
    # calculating y coordinates for 1000 evenly spaced points in (1,-1)
    for x in np.linspace(1, -1, 1000):
        y = -math.sqrt(1 - x ** 2)
        pos2.append([x, y])
        if len(pos2) > 1:
            adj2.append([length - 1, length])
        length = length + 1

    pos2 = np.array(pos2)
    adj2 = np.array(adj2)
    graph_item_2.setData(pos=pos2, adj=adj2, size=0.07)

if __name__ == '__main__':
    position = [(-0.5,0), (0.5,0)]
    adjacency = [(0,1)]

    w = pg.GraphicsWindow()
    w.setWindowTitle('Title of the window') 
    v = w.addViewBox()
    v.setAspectLocked()
    g = Graph()
    v.addItem(g)

    g.setData(pos=np.array(position), adj=np.array(adjacency), pxMode=False, size=0.1)

    g2 = pg.GraphItem()
    v.addItem(g2)
    g3 = pg.GraphItem()
    v.addItem(g3)

    plot_poincare_disc(g2,g3)

    import sys

    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
        QtGui.QGuiApplication.instance().exec_()

I know, although, inside of the circle does not contain any scatter point, that is why it does not invoke any event. Is there a possibility to make inside hollow clickable?

Edit1: Code replaced by minimal, complete and meaningful code.

Answer 1

Instead of drawing the points and generating the circumference, a better strategy is to create a class that draws a transparent circle, creating a signal indicating the position of the click using the mousePressEvent method, the class from which it inherits must be QGraphicsObject :

import pyqtgraph as pg
import numpy as np
import math
from pyqtgraph.Qt import QtCore, QtGui

class Graph(pg.GraphItem):
    def __init__(self):
        ...


# Construct a unit radius circle for the graph
class EllipseObject(QtGui.QGraphicsObject):
    sigClicked = QtCore.pyqtSignal(float, float)
    def __init__(self, center= (0.0, 0.0), radius=1.0, pen=QtGui.QPen(QtCore.Qt.white)):
        QtGui.QGraphicsObject.__init__(self)
        self.center = center
        self.radius = radius
        self.pen = pen

    def boundingRect(self):
        rect = QtCore.QRectF(0, 0, 2*self.radius, 2*self.radius)
        rect.moveCenter(QtCore.QPointF(*self.center))
        return rect

    def paint(self, painter, option, widget):
        painter.setPen(self.pen)
        painter.drawEllipse(self.boundingRect())

    def mousePressEvent(self, event):
        p = event.pos()
        self.sigClicked.emit(p.x(), p.y())
        QtGui.QGraphicsEllipseItem.mousePressEvent(self, event)

if __name__ == '__main__':
    position = [(-0.5,0), (0.5,0)]
    adjacency = [(0,1)]
    w = pg.GraphicsWindow()
    w.setWindowTitle('Title of the window') 
    v = w.addViewBox()
    v.setAspectLocked()
    g = Graph()
    v.addItem(g)

    g.setData(pos=np.array(position), adj=np.array(adjacency), pxMode=False, size=0.1)
    item = EllipseObject()
    item.sigClicked.connect(lambda x, y: print(x, y))
    v.addItem(item)

    import sys

    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
        QtGui.QApplication.instance().exec_()