[PyQt] Stuttered Mouse Tracking

Power_Broker · (This post was last modified: Nov-05-2020, 02:34 AM by Power_Broker.)

I'm trying to use PyQt5 to create a GUI that has a scrollable area with a large picture. The picture is in the scrollable area and I want to use my mouse to smoothly click and drag the image around. I have it working, to where I can click and drag, but it's extremely laggy/noisy. I have some debug print statements, and it looks like the problem lies in wildly imprecise results from PyQt5's mouse event member: event.pos().x().

Been racking my brains for a long time and idk how to fix it so any help is greatly appreciated.

Main program:

import sys
from PyQt5.QtCore import pyqtSlot
from PyQt5.QtGui import QPixmap
from PyQt5.QtWidgets import QApplication, QMainWindow
from gui import Ui_MainWindow


class AppWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
        
        self.ui.label.moved.connect(self.move_image)
        
        pixmap = QPixmap('color.jpg')
        self.ui.label.setPixmap(pixmap)
        self.ui.hsb = self.ui.scrollArea.horizontalScrollBar()
        
        self.show()
    
    @pyqtSlot(list)
    def move_image(self, data):
        try:
            self.prev_points = self.cur_points
        except:
            self.cur_points  = data
            self.prev_points = self.cur_points
            
            return
        
        self.cur_points = data
        
        hsb = self.ui.scrollArea.horizontalScrollBar()
        vsb = self.ui.scrollArea.verticalScrollBar()
        
        scroll_x = self.cur_points[0] - self.prev_points[0]
        scroll_y = self.cur_points[1] - self.prev_points[1]
        
        hsb_pos = hsb.value() - scroll_x
        vsb_pos = vsb.value() - scroll_y
        
        print('pre: \t {}'.format(self.prev_points))
        print('cur: \t {}'.format(self.cur_points))
        print('scr X: \t [{}, {}]'.format(scroll_x, scroll_y))
        print('pre val: [{}, {}]'.format(hsb.value(), vsb.value()))
        
        if hsb_pos >= hsb.minimum() and hsb_pos <= hsb.maximum():
            hsb.setValue(hsb.value() - scroll_x)
        
        if vsb_pos >= vsb.minimum() and vsb_pos <= vsb.maximum():
            vsb.setValue(vsb.value() - scroll_y)
        
        print('pos val: [{}, {}]'.format(hsb.value(), vsb.value()))
        print('\n')
        

def main():
    app = QApplication(sys.argv)
    w   = AppWindow()
    w.show()
    sys.exit(app.exec_())


if __name__ == '__main__':
    main()

gui.py:

# -*- coding: utf-8 -*-

# Form implementation generated from reading ui file 'gui.ui'
#
# Created by: PyQt5 UI code generator 5.12.2
#
# WARNING! All changes made in this file will be lost!

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(270, 224)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
        self.gridLayout.setObjectName("gridLayout")
        self.scrollArea = QtWidgets.QScrollArea(self.centralwidget)
        self.scrollArea.setWidgetResizable(True)
        self.scrollArea.setObjectName("scrollArea")
        self.scrollAreaWidgetContents = QtWidgets.QWidget()
        self.scrollAreaWidgetContents.setGeometry(QtCore.QRect(0, 0, 250, 163))
        self.scrollAreaWidgetContents.setObjectName("scrollAreaWidgetContents")
        self.gridLayout_2 = QtWidgets.QGridLayout(self.scrollAreaWidgetContents)
        self.gridLayout_2.setObjectName("gridLayout_2")
        self.label = mouseLabel(self.scrollAreaWidgetContents)
        self.label.setText("")
        self.label.setObjectName("label")
        self.gridLayout_2.addWidget(self.label, 0, 0, 1, 1)
        self.scrollArea.setWidget(self.scrollAreaWidgetContents)
        self.gridLayout.addWidget(self.scrollArea, 0, 0, 1, 1)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 270, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))


from customlabel import mouseLabel


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

customlabel.py:

from PyQt5.QtGui import *
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *


class mouseLabel(QLabel):
    moved = pyqtSignal(list)
    
    def __init__(self, parent=None):
        super(mouseLabel, self).__init__(parent)
        self.setMouseTracking(True)
        self.clicked = False

    def mouseMoveEvent(self, event):
        if self.clicked:
            self.moved.emit([event.pos().x(), event.pos().y()])

    def mousePressEvent(self, event):
        if event.button() == 1:
            self.clicked = True
        
    def mouseReleaseEvent(self, event):
        if event.button() == 1:
            self.clicked = False

Axel_Erfurt · (This post was last modified: Nov-05-2020, 09:09 AM by Axel_Erfurt.)

this works better (for me)

main

import sys
from PyQt5.QtCore import pyqtSlot
from PyQt5.QtGui import QPixmap
from PyQt5.QtWidgets import QApplication, QMainWindow
from gui import Ui_MainWindow


class AppWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
         
         
        pixmap = QPixmap('color.jpg')
        self.ui.label.setPixmap(pixmap)
        self.ui.hsb = self.ui.scrollArea.horizontalScrollBar()
         
        self.show()
         
 
def main():
    app = QApplication(sys.argv)
    w   = AppWindow()
    w.show()
    sys.exit(app.exec_())
 
 
if __name__ == '__main__':
    main()

customlabel

from PyQt5.QtGui import *
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
 
 
class mouseLabel(QLabel):
     
    def __init__(self, parent=None):
        super(mouseLabel, self).__init__(parent)
        self.setMouseTracking(True)
        self.clicked = False
    
    def mousePressEvent(self, event):
        if event.button() == 1:
            self.clicked = True
            self.oldPos = event.globalPos()

    def mouseMoveEvent(self, event):
        if self.clicked:
            delta = QPoint(event.globalPos() - self.oldPos)
            self.move(self.x() + delta.x(), self.y() + delta.y())
            self.oldPos = event.globalPos()

    def mouseReleaseEvent(self, event):
        if event.button() == 1:
            self.clicked = False

Axel_Erfurt · Nov-05-2020, 09:16 AM

a version all in one

import sys
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        self.centralwidget = QWidget(MainWindow)
        self.gridLayout = QGridLayout(self.centralwidget)
        self.scrollArea = QScrollArea(self.centralwidget)
        self.scrollArea.setWidgetResizable(True)
        self.scrollAreaWidgetContents = QWidget()
        self.gridLayout_2 = QGridLayout(self.scrollAreaWidgetContents)
        self.label = mouseLabel(self.scrollAreaWidgetContents)
        self.label.setText("")
        self.gridLayout_2.addWidget(self.label)
        self.scrollArea.setWidget(self.scrollAreaWidgetContents)
        self.gridLayout.addWidget(self.scrollArea)
        MainWindow.setCentralWidget(self.centralwidget)


class mouseLabel(QLabel):
     
    def __init__(self, parent=None):
        super(mouseLabel, self).__init__(parent)
        self.setMouseTracking(True)
        self.clicked = False
    
    def mousePressEvent(self, event):
        if event.button() == 1:
            self.clicked = True
            self.oldPos = event.globalPos()

    def mouseMoveEvent(self, event):
            if self.clicked:
                delta = QPoint(event.globalPos() - self.oldPos)
                self.move(self.x() + delta.x(), self.y() + delta.y())
                self.oldPos = event.globalPos()

    def mouseReleaseEvent(self, event):
        if event.button() == 1:
            self.clicked = False
 
 
class AppWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
                
        pixmap = QPixmap('color.jpg')
        self.ui.label.setPixmap(pixmap)
        self.ui.hsb = self.ui.scrollArea.horizontalScrollBar()
        self.resize(270, 224)
        self.show()
         
 
def main():
    app = QApplication(sys.argv)
    w   = AppWindow()
    w.show()
    sys.exit(app.exec_())
 
 
if __name__ == '__main__':
    main()

Power_Broker · Nov-05-2020, 06:30 PM

Omg, it works perfectly! Thanks!

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[PyQt] Stuttered Mouse Tracking

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