Develop Reference

How to integrate a cursor in a QtWidgets app

I am new to QtWidgets and trying to build an app in QtWidgets and Python (3.x). the end goal of the app is to show images and a
superposed cursor (to be exact, a "plus" sign of 2cm) that can be moved along the image reacting to mouse events. I concentrate now first on this cursor. So far, I read examples on how to do it on matplotlib. however, i have trouble to understand how to integrate matplotlib on my code.
Also, is matplotlib the easiest way to do it on this code. or there might be a better way to do it.
any hint would be helpful
thank you in advance.
here is my desired output and the code of my app
import sys
from PySide2 import QtWidgets
from vispy import scene
from PySide2.QtCore import QMetaObject
from PySide2.QtWidgets import *
class SimpleItem(QtWidgets.QGraphicsItem):
def __init__(self):
QtWidgets.QGraphicsItem.__init__(self)
self.setFlag(QtWidgets.QGraphicsItem.ItemIsMovable, True)
def boundingRect(self):
penWidth = 1.0
return QRectF(-10 - penWidth / 2, -10 - penWidth / 2,
20 + penWidth, 20 + penWidth)
def paint(self, painter, option, widget):
rect = self.boundingRect()
painter.drawRect(rect)
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
if not MainWindow.objectName():
MainWindow.setObjectName("MainWindow")
MainWindow.resize(800, 600)
self.centralwidget = QWidget(MainWindow)
self.centralwidget.setObjectName("centralwidget")
self.gridLayout = QGridLayout(self.centralwidget)
self.gridLayout.setObjectName("gridLayout")
self.groupBox = QGroupBox(self.centralwidget)
self.groupBox.setObjectName("groupBox")
self.gridLayout.addWidget(self.groupBox, 0, 0, 1, 1)
MainWindow.setCentralWidget(self.centralwidget)
QMetaObject.connectSlotsByName(MainWindow)
class MainWindow(QtWidgets.QMainWindow):
def __init__(self):
super(MainWindow, self).__init__()
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
# OpenGL drawing surface
self.canvas = scene.SceneCanvas(keys='interactive')
self.canvas.create_native()
self.canvas.native.setParent(self)
self.view = self.canvas.central_widget.add_view()
self.view.bgcolor = '#ffffff' # set the canva to a white background
scene2 = QGraphicsScene()
item = SimpleItem()
scene2.addItem(item)
self.setWindowTitle('MyApp')
def main():
import ctypes
ctypes.windll.shell32.SetCurrentProcessExplicitAppUserModelID('my_gui')
app = QtWidgets.QApplication([])
main_window = MainWindow()
main_window.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
edit: I added a class (here it is a rectangle just as an example) to illustrate my problem. i have trouble integrating that snippet of the code (with SimpleItem) to OpenGL canvas

You can use the QApplication.setOverrideCursor method to assign a .png image file as your cursor when it appears inside of the Qt program.
Here is an example that is mostly based on the code in your question. And below is a gif that demonstrates the example. And the last image is the image I used in the code as cursor.png
Hope this helps
import sys
from PySide2.QtCore import *
from PySide2.QtWidgets import *
from PySide2.QtGui import *
class SimpleItem(QtWidgets.QGraphicsItem):
def __init__(self):
QtWidgets.QGraphicsItem.__init__(self)
self.setFlag(QtWidgets.QGraphicsItem.ItemIsMovable, True)
self._brush = QBrush(Qt.black)
def boundingRect(self):
penWidth = 1.0
return QRectF(-50 - penWidth / 2, -50 - penWidth / 2,
50 + penWidth, 50 + penWidth)
def paint(self, painter, option, widget):
rect = self.boundingRect()
painter.drawRect(rect)
painter.fillRect(rect, self._brush)
class MainWindow(QtWidgets.QMainWindow):
def __init__(self):
super(MainWindow, self).__init__()
self.resize(800, 600)
self.scene = QGraphicsScene()
self.canvas = scene.SceneCanvas(keys='interactive')
self.view = QGraphicsView(self.scene)
item = SimpleItem()
self.scene.addItem(item)
self.setCentralWidget(self.view)
self.setWindowTitle('MyApp')
def main():
import ctypes
ctypes.windll.shell32.SetCurrentProcessExplicitAppUserModelID('my_gui')
app = QtWidgets.QApplication([])
app.setOverrideCursor(QCursor(QPixmap('cursor.png')))
main_window = MainWindow()
main_window.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()

PyQt5 drawing lines that have mouse events

I have an application where I draw 2 custom widgets and then draw a line between them. I want to add a mousePressEvent to the line.
What would be the best way to do this?
I suppose I could create a QWidget of x pixel thickness and y length and then fill in the whole widget with the colour I want the line to have. Then the QWidget has the mousePressEvent that I can override. This doesn't seem like the most elegant solution and feels more like a workaround. Is there a better way?
import sys
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPaintEvent, QPainter, QPen, QFont
from PyQt5.QtWidgets import QApplication, QMainWindow, QWidget, QLabel
class MyWidget(QWidget):
def __init__(self, name, parent):
super().__init__(parent)
self.setAutoFillBackground(True)
self.setFixedSize(300, 100)
p = self.palette()
p.setColor(self.backgroundRole(), Qt.white)
self.setPalette(p)
lbl_name = QLabel(name, self)
lbl_name.setFont(QFont('Arial', 16))
lbl_name.move((self.width() - lbl_name.width()) / 2, self.height()/2 - lbl_name.height()/2)
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
self.main_widget = QWidget(self)
self.widget_1 = MyWidget("Widget 1", self)
self.widget_1.move(50, 50)
self.widget_2 = MyWidget("Widget 2", self)
self.widget_2.move(700, 600)
self.resize(1200, 800)
self.setCentralWidget(self.main_widget)
def paintEvent(self, a0: QPaintEvent) -> None:
super().paintEvent(a0)
painter = QPainter(self)
painter.setPen(QPen(Qt.red, 3, Qt.SolidLine))
widget_1_x = self.widget_1.pos().x() + self.widget_1.size().width()
widget_1_y = self.widget_1.pos().y() + self.widget_1.size().height() / 2
widget_2_x = self.widget_2.pos().x()
widget_2_y = self.widget_2.pos().y() + self.widget_2.size().height() / 2
halfway_x = widget_1_x + (widget_2_x - widget_1_x) / 2
# add mousePressEvents to these lines:
painter.drawLine(widget_1_x, widget_1_y, halfway_x, widget_1_y)
painter.drawLine(halfway_x, widget_1_y, halfway_x, widget_2_y)
painter.drawLine(halfway_x, widget_2_y, widget_2_x, widget_2_y)
if __name__ == "__main__":
app = QApplication(sys.argv)
myapp = MainWindow()
myapp.show()
sys.exit(app.exec_())
How the above code looks like when run

PyQt5: How to place a QPixmap on top of another QPixmap?

I would like to place a QPixmap on another QPixmap. Both have the same size, so I would just like to make an overlay. The overlay image has a transparent elipse in the middle. I figure they should be QPixmap format, however I dont know how to place them on top of each other and keep them in place when resizing the window. This is my code displaying how my background images are placed. I have attached a image explaining what i want.
import sys
from PyQt5 import QtGui ,QtWidgets, uic
from PyQt5.QtCore import Qt
class Ergolab(QtWidgets.QMainWindow):
def __init__(self, *args, **kwargs):
super(Ergolab, self).__init__(*args, **kwargs)
# Load the UI Page
self.ui = uic.loadUi("mainwindow.ui",self)
self.pixmap1 = QtGui.QPixmap('C:/Users/Frede/Desktop/img1.jpg')
self.shoflexLLabel.setPixmap(self.pixmap1.scaled(self.shoflexLLabel.size(), Qt.KeepAspectRatio, Qt.SmoothTransformation))
self.shoflexLLabel.setSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
self.shoflexLLabel.setMinimumSize(150, 150)
self.shoflexLLabel.resize(800, 600)
self.pixmap2 = QtGui.QPixmap('C:/Users/Frede/Desktop/img2.jpg')
self.shoflexRLabel.setPixmap(self.pixmap2.scaled(self.shoflexRLabel.size(), Qt.KeepAspectRatio, Qt.SmoothTransformation))
self.shoflexRLabel.setSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
self.shoflexRLabel.setMinimumSize(150, 150)
self.shoflexRLabel.resize(800, 600)
def resizeEvent(self, event):
scaledSize = self.shoflexLLabel.size()
if not self.shoflexLLabel.pixmap() or scaledSize != self.shoflexLLabel.pixmap().size():
self.updateLabel()
def updateLabel(self):
self.shoflexLLabel.setPixmap(self.pixmap1.scaled(
self.shoflexLLabel.size(), Qt.KeepAspectRatio,
Qt.SmoothTransformation))
self.shoflexRLabel.setPixmap(self.pixmap2.scaled(
self.shoflexRLabel.size(), Qt.KeepAspectRatio,
Qt.SmoothTransformation))
def main():
app = QtWidgets.QApplication(sys.argv)
main = Ergolab()
main.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
This is the result I would like:

You must use QPainter by setting the circle as a clip path:
import sys
from PyQt5 import QtCore, QtGui, QtWidgets
class MainWindow(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
label = QtWidgets.QLabel()
self.setCentralWidget(label)
base_pixmap = QtGui.QPixmap("background.png")
overlay_pixmap = QtGui.QPixmap("overlay.png")
radius = 300
r = QtCore.QRectF()
r.setSize(radius * QtCore.QSizeF(1, 1))
r.moveCenter(base_pixmap.rect().center())
path = QtGui.QPainterPath()
path.addEllipse(r)
painter = QtGui.QPainter(base_pixmap)
painter.setRenderHints(
QtGui.QPainter.Antialiasing | QtGui.QPainter.SmoothPixmapTransform
)
painter.setClipPath(path, QtCore.Qt.IntersectClip)
painter.drawPixmap(QtCore.QPoint(), overlay_pixmap)
painter.end()
label.setPixmap(base_pixmap)
if __name__ == "__main__":
app = QtWidgets.QApplication(sys.argv)
w = MainWindow()
w.show()
sys.exit(app.exec_())

How to update a QPainter pixmap based on QTimer

I would like to continuously rotate a QPainter pixmap every tick based from a QTimer - in this example a clock arm. I can rotate the clock arm, however I dont have the skills to make the rotation dynamic. Here is the clock I would like to make and below is my sample code. Let me know if you can help me on the way, thanks!
import sys
import random
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtCore import Qt
class MainWindow(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
self.label = QtWidgets.QLabel()
self.setCentralWidget(self.label)
self.Clock_pixmap = QtGui.QPixmap("clock.png")
self.Arm_pixmap = QtGui.QPixmap("clockarm.png")
self.painter = QtGui.QPainter(self.Clock_pixmap)
self.painter.setRenderHints(QtGui.QPainter.Antialiasing | QtGui.QPainter.SmoothPixmapTransform)
self.painter.drawPixmap(QtCore.QPoint(), self.Arm_pixmap)
self.painter.end()
self.label.setPixmap(self.Clock_pixmap.scaled(self.label.size(), Qt.KeepAspectRatio, Qt.SmoothTransformation))
self.label.setSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
self.label.setMinimumSize(150, 150)
self.w1 = self.Arm_pixmap.width()/2
self.h1 = self.Arm_pixmap.height()/2
self.rotationData = random.sample(range(100), 100)
timer = QtCore.QTimer(self, timeout=self.rotateArm, interval=100)
timer.start()
self.n=0
def rotateArm(self):
self.n+=1
self.painter.translate(self.w1,self.h1)
self.painter.rotate(self.rotationData[self.n])
self.painter.translate(-self.w1,-self.h1)
self.update()
if __name__ == "__main__":
app = QtWidgets.QApplication(sys.argv)
w = MainWindow()
w.show()
sys.exit(app.exec_())

You are painting on a QPainter where you indicated that it was finished painting since you used the end() method. So it is not necessary to make a class attribute to QPainter but only a local variable. Considering the above, the solution is:
import sys
import random
from PyQt5 import QtCore, QtGui, QtWidgets
class MainWindow(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super().__init__(parent)
self._angle = 0
self.label = QtWidgets.QLabel()
self.setCentralWidget(self.label)
self.clock_pixmap = QtGui.QPixmap("clock.png")
self.arm_pixmap = QtGui.QPixmap("clockarm.png")
rotation_data = random.sample(range(100), 100)
self.data_iter = iter(rotation_data)
timer = QtCore.QTimer(self, timeout=self.rotate_arm, interval=100)
timer.start()
def rotate_arm(self):
try:
angle = next(self.data_iter)
except StopIteration:
pass
else:
self.draw(angle)
def draw(self, angle):
pixmap = self.clock_pixmap.copy()
painter = QtGui.QPainter(pixmap)
painter.setRenderHints(
QtGui.QPainter.Antialiasing | QtGui.QPainter.SmoothPixmapTransform
)
painter.translate(pixmap.rect().center())
painter.rotate(angle)
painter.translate(-pixmap.rect().center())
painter.drawPixmap(QtCore.QPoint(), self.arm_pixmap)
painter.end()
self.label.setPixmap(pixmap)
if __name__ == "__main__":
app = QtWidgets.QApplication(sys.argv)
w = MainWindow()
w.show()
sys.exit(app.exec_())

how to set the background color for draw text?

I want to set the background for text, which means that I want to set the color of the rectangle contains the text. I have tested QPainter.setBackground, but it do not work. This is my code:
import sys
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
class MyLabel(QLabel):
def __init__(self):
super(MyLabel, self).__init__()
self.setMinimumHeight(200)
self.setMinimumWidth(200)
def paintEvent(self, QPaintEvent):
super(MyLabel, self).paintEvent(QPaintEvent)
pos = QPoint(50, 50)
painter = QPainter(self)
brush = QBrush()
brush.setColor(QColor(255,0,0))
painter.setBackgroundMode(Qt.OpaqueMode)
painter.setBackground(brush)
painter.drawText(pos, 'hello,world')
class Window(QWidget):
def __init__(self):
super(Window, self).__init__()
layout = QHBoxLayout(self)
self.label = MyLabel()
layout.addWidget(self.label)
if __name__ == '__main__':
app = QApplication(sys.argv)
window = Window()
window.show()
sys.exit(app.exec_())
What I want is:
Thanks for any help.

It is not necessary to implement a personalized QLabel, it is enough to set the background color through Qt Style Sheet, also do not use a layout if you want to establish a certain position
import sys
from PyQt5 import QtCore, QtGui, QtWidgets
class Window(QtWidgets.QWidget):
def __init__(self):
super(Window, self).__init__()
self.label = QtWidgets.QLabel("hello,world", self)
self.label.adjustSize()
self.label.setStyleSheet(
"background-color: {};".format(QtGui.QColor(255, 0, 0).name())
)
self.label.move(QtCore.QPoint(50, 50))
if __name__ == "__main__":
app = QtWidgets.QApplication(sys.argv)
window = Window()
window.resize(640, 480)
window.show()
sys.exit(app.exec_())