CODEWITHSUNDEEP
python-3.xqtpyqt5
notEmissary
notEmissary

Reputation: 65

PyQt5 - How to draw a dot on mouse click position?

I am trying to draw a dot on my main window, but the dot is not shown.

I've tried bounding mousePressEvent to paintEvent, but it didn't work as well. Here's current version of my code(which is not working too). Also I tried place a point with drawPoint method and it didn't work too.

import sys
from PyQt5 import QtWidgets, QtGui, QtCore, uic


class GUI(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        uic.loadUi('gui.ui', self)
        self.setFixedSize(self.size())
        self.show()

    def mousePressEvent(self, e):
        print(e.pos())
        qp = QtGui.QPainter()
        qp.begin(self)
        qp.setPen(QtCore.Qt.red)
        qp.drawEllipse(e.pos().x(), e.pos().y(), 10, 10)
        qp.end()
        self.update()


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    window = GUI()
    sys.exit(app.exec_())

I know that mousePressEvent is working since I get coords of the click.

I am okay to change methods of dot-placing or type of dots to place, but it should have customizable color and size.

Upvotes: 3

Views: 4504

Answers (1)

eyllanesc
eyllanesc

Reputation: 243973

You should only draw within the paintEvent method, and this paint does not save memory so if you want to graph several points you must store them in some container, for example using QPolygon.

paintEvent() is called every time you call update() or repaint(), for example it is called every time it is resized, the window is moved, etc.

import sys
from PyQt5 import QtWidgets, QtGui, QtCore, uic


class GUI(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        uic.loadUi('gui.ui', self)
        self.setFixedSize(self.size())
        self.show()
        self.points = QtGui.QPolygon()

    def mousePressEvent(self, e):
        self.points << e.pos()
        self.update()

    def paintEvent(self, ev):
        qp = QtGui.QPainter(self)
        qp.setRenderHint(QtGui.QPainter.Antialiasing)
        pen = QtGui.QPen(QtCore.Qt.red, 5)
        brush = QtGui.QBrush(QtCore.Qt.red)
        qp.setPen(pen)
        qp.setBrush(brush)
        for i in range(self.points.count()):
            qp.drawEllipse(self.points.point(i), 5, 5)
        # or 
        # qp.drawPoints(self.points)


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    window = GUI()
    sys.exit(app.exec_())

Upvotes: 3

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