QTreeView drag/drop handling

Oak77

@JonB Well, it's dramatically reduced already to what I thought was close to minimum, however I'll try to review it again. I do see few bits I can get rid off. But obviously, I need to keep two tree views and some basic stuff to make it work.

Oak77

OK, I went through imports and through the code and hopefully it's now very close to minimal.

from PyQt5 import QtCore, QtGui
from PyQt5.QtCore import Qt, QSize, pyqtSlot, pyqtSignal, QModelIndex
from PyQt5.QtWidgets import QWidget, QMainWindow, QDockWidget, QToolBar, QAction, QVBoxLayout, QSplitter, QSizePolicy, QTreeView, QTabWidget
import PyQt5.QtWidgets                                                                         
from PyQt5.QtGui import QStandardItemModel, QStandardItem

_DOCK_OPTS = PyQt5.QtWidgets.QMainWindow.AllowNestedDocks
_DOCK_OPTS |= PyQt5.QtWidgets.QMainWindow.AllowTabbedDocks

 
class TreeModel(QStandardItemModel):
    def __init__(self):
        QStandardItemModel.__init__(self)
        
    def supportedDropActions(self):
        return QtCore.Qt.MoveAction | QtCore.Qt.CopyAction 

    def mimeData(self, indexes):
        mimedata = QtCore.QMimeData()
        #mimedata.setData('text/xml', str(self.nodeFromIndex(indexes[0])))
        #print("xxx mimeData = " + str(mimeData))
        print("Starting mimeData....")
        print("Index:    " + str(indexes))
        print("------")
        print(str(self.nodeFromIndex(indexes[0])))
        print("------2")
        node = self.nodeFromIndex(indexes[0])
        print("Continuing mimeData....")
        #print("Node:   " + str(node.data()))
        #mimedata.setData('text/xml', str(node))
        #mimedata.setData('bstream', bstream)
        print("Continuing mimeData 2....")
        mimedata.setData('text/xml', 'mimeData')
        return mimedata

    def nodeFromIndex(self, index):
        print("Index2:    " + str(index))      
        ip = None
        if index.isValid() == True:
            ip = index.internalPointer()
            print("isValid...")
            print(str(ip))
        else:
            print(str(self.root))
            ip = self.root
        print("before return")
        return ip
        ##return index.internalPointer() if index.isValid() else self.root
        

    def mimeTypes(self):
        return ['text/xml']


    def dropMimeData(self, data, action, row, column, parent):
        print('dropMimeData %s %s %s %s' % (data.data('text/xml'), action, row, parent))
        return True
    
    def flags(self, index):
        if not index.isValid():
            return QtCore.Qt.ItemIsEnabled
        return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsDragEnabled | QtCore.Qt.ItemIsDropEnabled

# -----------------------------------------------------------------------------------------------------------------------------------    

class Window(QMainWindow):
    selIdxsSignal = pyqtSignal(QModelIndex)
    
    def __init__(self):
        QMainWindow.__init__(self)
        self.setWindowTitle("Test")
        self.resize(600,500)

        self.tb = self.addToolBar("Test") 
        self.ShowTitleBars = False
        self.setWidth = 1600
        secondQMainWindow = QMainWindow()
        self.detailWidget = QWidget()
        self.detailLayout = QVBoxLayout()
        self.detailWidget.setLayout(self.detailLayout)

        self.detailData = (    # Database-like test data            
            (1,       -1,     20,   'GroupA',       'Group A'      ,400,   0,    '',    False,   8,   '',   '',    0),
            (3,        1,      3,   'ItemA1',       'Item A1'      , 50,   0,    '',    False,   8,   '',   '',    0),
            (4,        1,      1,   'ItemA2',       'Item A2'      ,  0,   0,    '',    True,    8,   '',   '',    0),
            (5,        1,      8,   'ItemA3',       'Item A3'      , 90,   0,    '',    False,   8,   '',   '',    0),
            (6,        1,     10,   'ItemA4',       'Item A4'      ,120,   0,    '',    False,   8,   '',   '',    0),
            (7,        1,      4,   'ItemA5',       'Item A5'      , 70,   0,    ' kg', True,    8,   '',   '',    2),
            (8,       -1,     20,   'GroupB',       'Group B'      ,  0,   0,    '',    False,   8,   '',   '',    0),
            (9,        8,      7,   'ItemB1',       'Item B1'      ,  0,   0,    '',    True,    8,   '',   '',    0),
            (10,       8,      2,   'ItemB2',       'Item B2'      ,  0,   66,   '',    True,    8,   '',   '',    0),
            )
        
        self.sourceData = (    # Database-like test data 
            (1,       -1,      1,   'Item1',   'Item 1',     0,     0,    '',    False,     8,    '',     '',    0),
            (2,       -1,      2,   'Item2',   'Item 2',     0,     0,    '',    False,     8,    '',     '',    0),
            (3,       -1,      3,   'Item3',   'Item 3',     0,     0,    '',    False,     8,    '',     '',    0),
            (4,       -1,      4,   'Item4',   'Item 4',     0,     0,    '',    False,     8,    '',     '',    0),
            (5,       -1,      5,   'Item5',   'Item 5',     0,     0,    '',    False,     8,    '',     '',    0),
            (6,       -1,      6,   'Item6',   'Item 6',     0,     0,    '',    False,     8,    '',     '',    0),
            (7,       -1,      7,   'Item7',   'Item 7',     0,     0,    '',    False,     8,    '',     '',    0),
            (8,       -1,      8,   'Item8',   'Item 8',     0,     0,    '',    False,     8,    '',     '',    0),
            (9,       -1,      9,   'Item9',   'Item 9',     0,     0,    '',    False,     8,    '',     '',    0),
            (10,      -1,     10,   'Item10',  'Item 10',    0,     0,    '',    False,     8,    '',     '',    0),
            (11,      -1,     11,   'Item11',  'Item 11',    0,     0,    '',    False,     8,    '',     '',    0),
            (12,      -1,     12,   'Item12',  'Item 12',    0,     0,    '',    False,     8,    '',     '',    0),
            (20,      -1,     20,   'Item13',  'Item 13',    0,     0,    '',    False,     8,    '',     '',    0),
            (21,      -1,     21,   'Item14',  'Item 14',    0,     0,    '',    False,     8,    '',     '',    0),      
            )
 
        self.central = secondQMainWindow
        self.setDockOptions(_DOCK_OPTS)   #.dockNestingEnabled(True)
        self.dw1 = QDockWidget("Pre-set items")
        self.dw1.topLevelChanged.connect(self.HideTitleBar)
        self.dw1.setTitleBarWidget(QWidget(self.dw1))

        # Right treeview
        srcTreeView = QTreeView()
        srcTreeView.setIconSize(QSize(24,24))
        srcTreeView.setHeaderHidden(True)   
        srcTreeView.setDragEnabled(True)
        self.srcModel = TreeModel()
        srcroot = self.srcModel.invisibleRootItem()
        srcroot1 = QStandardItem("Group 1")
        srcroot.appendRow(srcroot1)
        srcroot2 = QStandardItem("Group 2")
        srcroot.appendRow(srcroot2)
        srcroot3 = QStandardItem("Group 3")
        srcroot.appendRow(srcroot3)
        for ID, ParentID, Type, Name, Label, Width, Height, Units, IsEditable, FontSize, FontVariant, NumberFormat, DecimalPlaces in self.sourceData:  # for each record, generate an item in a treeModel, used in QTreeView
            print("ID = " + str(ID))
            print("Name = " + Name)
            it = QStandardItem(Name)
            it.setData(ID)
            if ParentID == -1:
                srcroot1.appendRow(it)
            for item in self.iterItems(srcroot):
                #print(item.text())
                if item.data() == ParentID:
                    item.appendRow(it)
        srcTreeView.setModel(self.srcModel)
        self.dw1.setWidget(srcTreeView)
        srcTreeView.expandAll()
        srcTreeView.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.MinimumExpanding)                        
        self.addDockWidget(Qt.LeftDockWidgetArea, self.dw1)

        # Left treeview        
        self.dw4 = QDockWidget("Group Editor")
        self.dw4.topLevelChanged.connect(self.HideTitleBar)
        self.dw4.setTitleBarWidget(QWidget(self.dw4))        
        DetailW = QWidget()
        DetailW.setAcceptDrops(True)
        DetailSplitter = QSplitter()
        self.DetailTree = QTreeView()  
        self.DetailTree.setDragEnabled(True)
        self.treeModel = TreeModel()
        self.DetailTree.setHeaderHidden(True)   
        self.DetailTree.setAcceptDrops(True)
        self.DetailTree.setIconSize(QSize(24,24))
        DetailSplitter.addWidget(self.DetailTree)
        DetailSplitter.addWidget(self.detailWidget)
        self.dw4.setWidget(DetailSplitter)
        self.DetailTree.setObjectName = "DetailEditor"
        print("Check model:   " + str(self.DetailTree.model))

        
        root = self.treeModel.invisibleRootItem()
        root1 = QStandardItem("Master Group")
        root.appendRow(root1)
        for ID, ParentID, Type, Name, Label, Width, Height, Units, IsEditable, FontSize, FontVariant, NumberFormat, DecimalPlaces in self.detailData:  # for each record, generate an item in a treeModel, used in QTreeView
            print("ID = " + str(ID))
            print("Name = " + Name)
            it = QStandardItem(Name)
            it.setData(ID) 
            if ParentID == -1:
                root1.appendRow(it)
            for item in self.iterItems(root):
                #print(item.text())
                if item.data() == ParentID:
                    item.appendRow(it)
 
        self.DetailTree.setModel(self.treeModel)
        self.DetailTree.expandAll()
        self.DetailTree.selectionModel().selectionChanged.connect(self.selIdxSignalChangeHandler)  
        self.selIdxsSignal.connect(self.selectionChangeHandler) 
                
        self.addDockWidget(Qt.RightDockWidgetArea, self.dw4)    
      
        btn = QAction("A button",self)
        self.tb.addAction(btn)
          

    def selIdxSignalChangeHandler(self):
        self.selIdxsSignal.emit(self.DetailTree.selectionModel().selectedIndexes()[0])
        
    def selectionChangeHandler(self, Idx):
        print(str(Idx))
        IID = Idx.data(Qt.UserRole + 1)
        print("    Selection changed - IID = " + str(IID))
        tbName = self.findChild(QLineEdit, "txtText")
        tbWidth = self.findChild(QLineEdit, "txtWidth")
        tbHeight = self.findChild(QLineEdit, "txtHeight")
        tbDataType = self.findChild(QLineEdit, "txtType")
        tbUnit = self.findChild(QLineEdit, "txtUnit")
        tbDecimals = self.findChild(QLineEdit, "txtDecimals")
        row = self.getRowByIndex(Idx)
        if IID != None:
            print("Assigning properties")
            #tbName.setText(str(row[3]))
            #tbWidth.setText(str(row[5]))
            #tbHeight.setText(str(row[6]))
            #tbDataType.setText(str(row[2]))
            #tbUnit.setText(str(row[7]))
            #tbDecimals.setText(str(row[12]))

    
    def getRowByIndex(self, Index):
        model = self.treeModel
        print("### getRowByIndex")
        SelID = model.data(Index, Qt.UserRole+1)
        print("### Selected ID = " + str(SelID))
        row = None
        for i, ir in enumerate(self.detailData):
            if ir[0] == SelID:
                row = self.detailData[i]
                break
        return row

           
    def iterItems(self, root):    # get all items, credits to @ekhumuro answer
        def recurse(parent):
            for row in range(parent.rowCount()):
                for column in range(parent.columnCount()):
                    child = parent.child(row, column)
                    yield child
                    if child.hasChildren():
                        yield from recurse(child)
        if root is not None:
            yield from recurse(root) 
 
    #def dropMimeData(self, mimedata, action, row, column, parentIndex):
        #if action == Qt.IgnoreAction: 
            #return True
        #dragNode = mimedata.instance() 
        #parentNode = self.nodeFromIndex(parentIndex) 
        #newNode = deepcopy(dragNode) #<------ why copy? Why not just reparent?
        #newNode.setParent(parentNode) 
        #self.insertRow(len(parentNode)-1, parentIndex) 
        #self.emit(SIGNAL("dataChanged(QModelIndex,QModelIndex)"), parentIndex, parentIndex) 
        #print("Done mime data")
        #return True 
     
                
    def HideTitleBar(self):
        dockw = self.sender()
        if dockw.isFloating() == False and self.ShowTitleBars == False:
            dockw.setTitleBarWidget(QWidget(dockw))
       
         
            
# ----------------------------------------------------------------------------------------------------------------------------------------------------------------            
                       
if __name__ == '__main__':
    import sys
    app = PyQt5.QtWidgets.QApplication(sys.argv)
    window = Window()
    window.show()
    app.exec_()

JonB

@Oak77
So, just as an example, in order to reproduce your crash, it is necessary to have dock widgets, toolbars, tabs, menus, tool buttons, icons, pixmaps, palettes, colours, validators, and Python pickling? Then you must have one of the most complex situations/problems to diagnose that I have ever heard of in a Qt program, and it must be incredibly difficult to diagnose with all those interactions contributing. Best of luck, hopefully somebody will know why these contribute to the issue and give you the solution.

Oak77

@JonB said in QTreeView drag/drop handling:

@Oak77
So, just as an example, in order to reproduce your crash, it is necessary to have dock widgets, toolbars, tabs, menus, tool buttons, icons, pixmaps, palettes, colours, validators, and Python pickling?

I don't get it. I removed all dock widgets except the two in which the QTabTreeView sits, I removed all tabs, all icons, all tool buttons except one empty dummy, all icons, all pixmap references, all palettes, all colours, pickling, menus,...

Did you look into the previous code?

I mean you're right I could remove the (now basically empty) toolbar altogether and the QDockWidgets containers in which QTreeViews sit, but that would strip only few lines of code and didn't seem to be important. That does not affect the drag and drop part, which is basically in separate class at the beginning of the code.

I'm not saying I won't remove the remaining few extra objects, if you thing it's important. But from looking at your reply, it seems you just glanced at wrong code.

SGaist

AFAIK, you need to reimplement dropMimeData and there you insert the dropped data the way you want/need in your model.

Oak77

@SGaist Right, so I'm not doing that? Using:

    def dropMimeData(self, data, action, row, column, parent):
        print('dropMimeData %s %s %s %s' % (data.data('text/xml'), action, row, parent))
        return True

That's only printing data, I know. But if I understand it correctly, it's dependant on what's inside the mimeData and that in turn on reimplemented mimeData...(?). And that's where I'm stuck, perhaps because the selection model is so far beyond my full understanding.
What I'm trying to do is to retrieve the index, out of indexed row the data(), which should be an ID and get a datarow by that ID. Something I would do in VB.net using a ValueMember and thus it would be a trivial task. It's well possible I'm doing it wrong way, but I didn't find any usable examples for the job.
The code itself crashes on an attempt to use (or return) of index.internalPointer(). I took the original code from some examples, but they were used in QAbsstractModel, while I'm using QStandardItemModel. I'm quite lost as for how to debug this.

By the way, if anyone knows of a good, complete example that covers this (QTreeVeiw, QStandardItemModel /or feasible alternative/, items with value member), please just point me in that direction, I'm willing to start over :-).

Oak77

I think that my problem comes from the fact, that I am following (the only available AFAIK) examples made in PyQt4 (and Python 2.6 I guess, looking at print syntaxe).

Here's one taken from QTreeView with drag and drop support in PyQt
, which I converted (or attemted, at least) to PyQt5 and Python 3.6:

import sys
from PyQt5 import QtGui, QtCore
from PyQt5.QtWidgets import QMainWindow, QApplication, QTreeView, QAbstractItemView

class TreeModel(QtCore.QAbstractItemModel):
    def __init__(self):
        QtCore.QAbstractItemModel.__init__(self)
        self.nodes = ['node0', 'node1', 'node2']

    def index(self, row, column, parent):
        return self.createIndex(row, column, self.nodes[row])

    def parent(self, index):
        return QtCore.QModelIndex()

    def rowCount(self, index):
        if index.internalPointer() in self.nodes:
            return 0
        return len(self.nodes)

    def columnCount(self, index):
        return 1

    def data(self, index, role):
        if role == 0: 
            return index.internalPointer()
        else:
            return None

    def supportedDropActions(self): 
        return QtCore.Qt.CopyAction | QtCore.Qt.MoveAction         

    def flags(self, index):
        if not index.isValid():
            return QtCore.Qt.ItemIsEnabled
        return QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable | \
               QtCore.Qt.ItemIsDragEnabled | QtCore.Qt.ItemIsDropEnabled        

    def mimeTypes(self):
        return ['text/xml']

    def mimeData(self, indexes):
        mimedata = QtCore.QMimeData()
        mimedata.setData('text/xml', 'mimeData')
        return mimedata

    def dropMimeData(self, data, action, row, column, parent):
        print('dropMimeData %s %s %s %s' % (data.data('text/xml'), action, row, parent))
        return True


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

        self.treeModel = TreeModel()

        self.view = QTreeView()
        self.view.setModel(self.treeModel)
        self.view.setDragDropMode(QAbstractItemView.InternalMove)

        self.setCentralWidget(self.view)

def main():
    app = QApplication(sys.argv)
    form = MainForm()
    form.show()
    app.exec_()

if __name__ == '__main__':
    main()

It doesn't work either, with error:

Traceback (most recent call last):
  File "tree_sample9.py", line 44, in mimeData
    mimedata.setData('text/xml', 'mimeData')
TypeError: setData(self, str, Union[QByteArray, bytes, bytearray]): argument 2 has unexpected type 'str'

I tried couple of different examples and got a result like that in all cases. I know it might be me messing something up the conversion, but I have no idea what's wrong.
Could anyone advice please, what could be wrong? And/or perhaps someone knows a good working example for Drag&Drop support in PyQt5?

JonB

@Oak77 said in QTreeView drag/drop handling:

mimedata.setData('text/xml', 'mimeData')
TypeError: setData(self, str, Union[QByteArray, bytes, bytearray]): argument 2 has unexpected type 'str'

One of (something like) the following:

mimedata.setData('text/xml', QtCore.QByteArray('mimeData'))
mimedata.setData('text/xml', QtCore.QString('mimeData').toUtf8())
mimedata.setData('text/xml', 'mimeData'.encode())

Oak77

@JonB said in QTreeView drag/drop handling:

One of (something like) the following:

mimedata.setData('text/xml', QtCore.QByteArray('mimeData'))
mimedata.setData('text/xml', QtCore.QString('mimeData').toUtf8())
mimedata.setData('text/xml', 'mimeData'.encode())

Thank you very much! The very last option worked. I'm guessing I'm encoding the string into default UTF-8, but have no idea why it doesn't work without it, however now I can progress a bit and study this stuff...
Thank you again, that helped a lot!

SGaist

'This is a string'
b'This is not a string'

Python3 makes a strict distinction between bytes and string.

Oak77

@SGaist said in QTreeView drag/drop handling:

'This is a string'
b'This is not a string'
Python3 makes a strict distinction between bytes and string.

Right, but...:

'mimeData is a string'.encode()

...is a string in UTF-8, correct? What I was confused about is, that string (which I'd assume is UTF-8 by default) wouldn't work until it's encoded by encode() method, which with no argument, turns the string into UTF-8 string. I don't get why it crashed before and it's fine after encoding, especially because apparently it would work in PyQt4 (I don't have PyQt4 installed, didn't check, but all the references are with plain string). Not a big deal though, just my curiosity why.

JonB

@Oak77 said in QTreeView drag/drop handling:

I don't get why it crashed before and it's fine after encoding,

The error message told you that you were passing a str/QString and the method expects a QByteArray/bytes, as per the documentation. They are not the same. I can't comment about PyQt4 --- you'd have to look up changes, and Qt4/PyQt4 has changed at 5, and also Python from 2.x to 3.x if relevant --- but it's just a parameter type mismatch here, no mystery. (BTW, yes, encode() is UTF-8 default.)

SGaist

The encode method returns a bytes object.

Oak77

@JonB and @SGaist

Thank you for your explanation, both thanks to your comments and my 2 hours over docs and testing yesterday helped me. You might hate me though, through all that time I was unable to convert that QByteArray back to string :-). It makes me feel stupid, but looking into tons of confused threads, at least I'm not alone...

b = b'MyString'

...is a QByteArray, if I'm not completely lost. Then...

print(b.decode("utf-8"))

...should output (and does):

MyString

Then, when the same MyString string is set to data, we get:

print("   1 ----  " + str(data.data('text/xml')))

outputs a string:

1 ----  b'MyString'

And I would expect decoding it would give me a string:

print("   2 ----  " + str(data.data('text/xml').decode("utf-8")))

...but, I get an error:

Traceback (most recent call last):
  File "test4.py", line 35, in dropMimeData
    print("   2 ----  " + str(data.data('text/xml').decode("utf-8")))

OK, there's a brute, ugly way, but I don't anyone expect to embrace it:

print(str(data.data('text/xml'))[2:-1])

Output is correct:

MyString

I did google related threads, but none related to mimeData and it works with byte arrays as shown above. Maybe I'm getting old for this stuff :-)

SGaist

@Oak77 said in QTreeView drag/drop handling:

b = b'MyString'

...is a QByteArray, if I'm not completely lost.

Do not use single letter variable. It's a easy way to break all kinds of stuff like the interaction in the debugger.

That said, sorry, you are a bit lost. It's a Python bytes. The method you are calling accepts it as well as QByteArray that you would have to explicitly build. You cannot convert a bytes to a string by calling str() on it, you have to use the encode method. If you call str(your_bytes) you will get "b'MyString'".

Oak77

@SGaist Lost am I :-). I see you pointing out python bytes vs. QByteArray, makes sense, I'll study that. Thank you for caring to comment my rookie issues.