Pyqt4 - Drag And Drop

Hey I had been going through this tutorial for understanding drag and drop methods in PyQt4. However I am not able to understand the following points . It would be nice if somepne

Solution 1:

That tutorial is seriously outdated. QDrag.start is obsolete since Qt 4.3. QDrag.exec_ should be used instead.

As you can see from the docs for exec, it has a return value. setDropAction in dropEvent determines this value. It doesn't perform the move. That's why you need a self.button.move() to do the actual moving. So, what's the point of a setDropAction? You might need to know what kind of drag operation you did. Imagine you're implementing drag-drop between two list widgets. If you did a move operation, that means you need to remove the item from the source widget and create one in the target. If it was a copy operation, you can leave the original and just create a copy in the target.

setHotSpot/hotSpot is related to the setPixmap of a QDrag. You can display a QPixmap as you drag the item. hotSpot determines the positioning of the pixmap. The pixmap will be positioned such that the cursor will be at hotSpot relative to the top-left corner of the pixmap. So, in the case of that tutorial, it is rather pointless since there is no pixmap to be shown.

Here is a bit modified and updated version of that tutorial. Hopefully, I've included enough comments. You can move with Right-Click or copy with Shift + Right-Click:

#!/usr/bin/python# -*- coding: utf-8 -*-import sys
from PyQt4 import QtGui, QtCore


classButton(QtGui.QPushButton):
    defmouseMoveEvent(self, e):
        if e.buttons() != QtCore.Qt.RightButton:
            return# write the relative cursor position to mime data
        mimeData = QtCore.QMimeData()
        # simple string with 'x,y'
        mimeData.setText('%d,%d' % (e.x(), e.y()))

        # let's make it fancy. we'll show a "ghost" of the button as we drag# grab the button to a pixmap
        pixmap = QtGui.QPixmap.grabWidget(self)

        # below makes the pixmap half transparent
        painter = QtGui.QPainter(pixmap)
        painter.setCompositionMode(painter.CompositionMode_DestinationIn)
        painter.fillRect(pixmap.rect(), QtGui.QColor(0, 0, 0, 127))
        painter.end()

        # make a QDrag
        drag = QtGui.QDrag(self)
        # put our MimeData
        drag.setMimeData(mimeData)
        # set its Pixmap
        drag.setPixmap(pixmap)
        # shift the Pixmap so that it coincides with the cursor position
        drag.setHotSpot(e.pos())

        # start the drag operation# exec_ will return the accepted action from dropEventif drag.exec_(QtCore.Qt.CopyAction | QtCore.Qt.MoveAction) == QtCore.Qt.MoveAction:
            print'moved'else:
            print'copied'defmousePressEvent(self, e):
        QtGui.QPushButton.mousePressEvent(self, e)
        if e.button() == QtCore.Qt.LeftButton:
            print'press'classExample(QtGui.QWidget):
    def__init__(self):
        super(Example, self).__init__()
        self.initUI()


    definitUI(self):
        self.setAcceptDrops(True)

        button = Button('Button', self)
        button.move(100, 65)

        self.buttons = [button]

        self.setWindowTitle('Copy or Move')
        self.setGeometry(300, 300, 280, 150)


    defdragEnterEvent(self, e):
        e.accept()


    defdropEvent(self, e):
        # get the relative position from the mime data
        mime = e.mimeData().text()
        x, y = map(int, mime.split(','))

        if e.keyboardModifiers() & QtCore.Qt.ShiftModifier:
            # copy# so create a new button
            button = Button('Button', self)
            # move it to the position adjusted with the cursor position at drag
            button.move(e.pos()-QtCore.QPoint(x, y))
            # show it
            button.show()
            # store it
            self.buttons.append(button)
            # set the drop action as Copy
            e.setDropAction(QtCore.Qt.CopyAction)
        else:
            # move# so move the dragged button (i.e. event.source())
            e.source().move(e.pos()-QtCore.QPoint(x, y))
            # set the drop action as Move
            e.setDropAction(QtCore.Qt.MoveAction)
        # tell the QDrag we accepted it
        e.accept()



if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    ex = Example()
    ex.show()
    app.exec_()  

Solution 2:

Avaris' answer adapted for PyQt5 and Python 3.

#!/usr/bin/python# -*- coding: utf-8 -*-# Adapted for PyQt5 and Python 3 from Avaris' answer to# https://stackoverflow.com/questions/14395799/pyqt4-drag-and-dropimport sys
from PyQt5.QtWidgets import QPushButton, QWidget, QApplication
from PyQt5.QtCore import Qt, QMimeData, QPoint
from PyQt5.QtGui import QDrag, QPixmap, QPainter, QColor


classButton(QPushButton):
    defmouseMoveEvent(self, e):
        if e.buttons() != Qt.RightButton:
            return# write the relative cursor position to mime data
        mimeData = QMimeData()
        # simple string with 'x,y'
        mimeData.setText('%d,%d' % (e.x(), e.y()))

        # let's make it fancy. we'll show a "ghost" of the button as we drag# grab the button to a pixmap
        pixmap = QWidget.grab(self)

        # below makes the pixmap half transparent
        painter = QPainter(pixmap)
        painter.setCompositionMode(painter.CompositionMode_DestinationIn)
        painter.fillRect(pixmap.rect(), QColor(0, 0, 0, 127))
        painter.end()

        # make a QDrag
        drag = QDrag(self)
        # put our MimeData
        drag.setMimeData(mimeData)
        # set its Pixmap
        drag.setPixmap(pixmap)
        # shift the Pixmap so that it coincides with the cursor position
        drag.setHotSpot(e.pos())

        # start the drag operation# exec_ will return the accepted action from dropEventif drag.exec_(Qt.CopyAction | Qt.MoveAction) == Qt.MoveAction:
            print('moved')
        else:
            print('copied')


    defmousePressEvent(self, e):
        QPushButton.mousePressEvent(self, e)
        if e.button() == Qt.LeftButton:
            print('press')



classExample(QWidget):
    def__init__(self):
        super(Example, self).__init__()
        self.initUI()


    definitUI(self):
        self.setAcceptDrops(True)

        button = Button('Button', self)
        button.move(100, 65)

        self.buttons = [button]

        self.setWindowTitle('Copy or Move')
        self.setGeometry(300, 300, 280, 150)


    defdragEnterEvent(self, e):
        e.accept()


    defdropEvent(self, e):
        # get the relative position from the mime data
        mime = e.mimeData().text()
        x, y = map(int, mime.split(','))

        if e.keyboardModifiers() & Qt.ShiftModifier:
            # copy# so create a new button
            button = Button('Button', self)
            # move it to the position adjusted with the cursor position at drag
            button.move(e.pos()-QPoint(x, y))
            # show it
            button.show()
            # store it
            self.buttons.append(button)
            # set the drop action as Copy
            e.setDropAction(Qt.CopyAction)
        else:
            # move# so move the dragged button (i.e. event.source())
            e.source().move(e.pos()-QPoint(x, y))
            # set the drop action as Move
            e.setDropAction(Qt.MoveAction)
        # tell the QDrag we accepted it
        e.accept()



if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Example()
    ex.show()
    app.exec_()