[FIXED] PySide How to keep QLabel visible when I drag and drop?

Issue

I want to drag and drop labels, which my code does, but while moving it the label disappears. How can I keep the label visible while I am dragging it? I am using QDrag to copy the contents over.

I want to be able to drag these labels into a box with many slots, and have the label lock into one of the slots when its dropped in the vicinity. Since the label becomes invisible when being dragged, it is hard to visualize where exactly it will be dropped when I let go of the mouse button.

from PySide import QtCore, QtGui

myMimeType = 'application/MyWindow'

class MyLabel(QtGui.QLabel):
    def __init__(self, parent):
        super(MyLabel, self).__init__(parent)

        self.setStyleSheet("""
            background-color: black;
            color: white;
            font: bold;
            padding: 6px;
            border-width: 2px;
            border-style: solid;
            border-radius: 16px;
            border-color: white;
        """)

    def mousePressEvent(self, event):
        itemData   = QtCore.QByteArray()
        dataStream = QtCore.QDataStream(itemData, QtCore.QIODevice.WriteOnly)
        dataStream.writeString(self.text())
        dataStream << QtCore.QPoint(event.pos() - self.rect().topLeft())
    print dataStream

        mimeData = QtCore.QMimeData()
        mimeData.setData(myMimeType, itemData)
        mimeData.setText(self.text())

        drag = QtGui.QDrag(self)
        drag.setMimeData(mimeData)
        drag.setHotSpot(event.pos() - self.rect().topRight())

        self.hide()

        if drag.exec_(QtCore.Qt.MoveAction | QtCore.Qt.CopyAction, QtCore.Qt.CopyAction) == QtCore.Qt.MoveAction:
            self.close()

        else:
            self.show()


class MyFrame(QtGui.QFrame):
    def __init__(self, parent=None):
        super(MyFrame, self).__init__(parent)

        self.setStyleSheet("""
            background-color: lightgray;
            border-width: 2px;
            border-style: solid;
            border-color: black;
            margin: 2px;
        """)

        y = 6
        for labelNumber in range(6):
            label = MyLabel(self)
            label.setText("Label #{0}".format(labelNumber))
            label.move(6, y)
            label.show()

            y += label.height() + 2

        self.setAcceptDrops(True)

    def dragEnterEvent(self, event):
        if event.mimeData().hasFormat(myMimeType):
            if event.source() in self.children():
                event.setDropAction(QtCore.Qt.MoveAction)
                event.accept()

            else:
                event.acceptProposedAction()

        else:
            event.ignore()

    def dropEvent(self, event):
        if event.mimeData().hasFormat(myMimeType):
            mime       = event.mimeData()
            itemData   = mime.data(myMimeType)
            dataStream = QtCore.QDataStream(itemData, QtCore.QIODevice.ReadOnly)

            text = QtCore.QByteArray()
            offset = QtCore.QPoint()
            dataStream >> text >> offset

            newLabel = MyLabel(self)
            newLabel.setText(event.mimeData().text())
            newLabel.move(event.pos() - offset)
            newLabel.show()

            if event.source() in self.children():
                event.setDropAction(QtCore.Qt.MoveAction)
                event.accept()

            else:
                event.acceptProposedAction()

        else:
            event.ignore()

class MyWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MyWindow, self).__init__(parent)

        self.myFrame = MyFrame(self)

        self.setCentralWidget(self.myFrame)

if __name__ == "__main__":
    import sys

    app = QtGui.QApplication(sys.argv)
    app.setApplicationName('MyWindow')

    main = MyWindow()
    main.resize(333, 333)
    main.move(app.desktop().screen().rect().center() - main.rect().center())
    main.show()

    sys.exit(app.exec_())

Solution

You have to save the widget and set it in the QDrag:

from PySide import QtCore, QtGui

myMimeType = "application/MyWindow"


class MyLabel(QtGui.QLabel):
    def __init__(self, parent):
        super(MyLabel, self).__init__(parent)

        self.setStyleSheet(
            """
            background-color: black;
            color: white;
            font: bold;
            padding: 6px;
            border-width: 2px;
            border-style: solid;
            border-radius: 16px;
            border-color: white;
        """
        )

    def mousePressEvent(self, event):
        itemData = QtCore.QByteArray()
        dataStream = QtCore.QDataStream(itemData, QtCore.QIODevice.WriteOnly)
        dataStream.writeString(self.text())
        dataStream << QtCore.QPoint(event.pos() - self.rect().topLeft())

        mimeData = QtCore.QMimeData()
        mimeData.setData(myMimeType, itemData)
        mimeData.setText(self.text())

        drag = QtGui.QDrag(self)
        drag.setMimeData(mimeData)
        drag.setHotSpot(event.pos())
        # pixmap = self.grab()
        pixmap = QtGui.QPixmap(self.size())
        self.render(pixmap)
        drag.setPixmap(pixmap)
        self.hide()

        action = drag.exec_(
            QtCore.Qt.MoveAction | QtCore.Qt.CopyAction, QtCore.Qt.CopyAction
        )
        if action == QtCore.Qt.MoveAction:
            self.deleteLater()
        else:
            self.show()


class MyFrame(QtGui.QFrame):
    def __init__(self, parent=None):
        super(MyFrame, self).__init__(parent)

        self.setStyleSheet(
            """
            background-color: lightgray;
            border-width: 2px;
            border-style: solid;
            border-color: black;
            margin: 2px;
        """
        )

        y = 6
        for labelNumber in range(6):
            label = MyLabel(self)
            label.setText("Label #{0}".format(labelNumber))
            label.move(6, y)
            label.show()

            y += label.height() + 2

        self.setAcceptDrops(True)

    def dragEnterEvent(self, event):
        if event.mimeData().hasFormat(myMimeType):
            if event.source() in self.children():
                event.acceptProposedAction()

    def dropEvent(self, event):
        if event.mimeData().hasFormat(myMimeType):
            if (
                event.source() in self.children()
                and event.possibleActions() & QtCore.Qt.MoveAction
            ):
                event.acceptProposedAction()
                mime = event.mimeData()
                itemData = mime.data(myMimeType)
                dataStream = QtCore.QDataStream(itemData, QtCore.QIODevice.ReadOnly)

                text = QtCore.QByteArray()
                offset = QtCore.QPoint()
                dataStream >> text >> offset

                newLabel = MyLabel(self)
                newLabel.setText(event.mimeData().text())
                newLabel.move(event.pos() - offset)
                newLabel.show()
                event.setDropAction(QtCore.Qt.MoveAction)
        else:
            event.ignore()


class MyWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MyWindow, self).__init__(parent)
        self.myFrame = MyFrame()
        self.setCentralWidget(self.myFrame)


if __name__ == "__main__":
    import sys

    app = QtGui.QApplication(sys.argv)
    app.setApplicationName("MyWindow")
    main = MyWindow()
    main.resize(333, 333)
    main.show()
    sys.exit(app.exec_())

Answered By - eyllanesc