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MitchellKehn/rich_drag_and_drop.py

Last active January 21, 2024 01:50
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[Drag and drop between item widgets with custom types] normally drag-and-drop between item widgets doesn't preserve subclass types for custom items. This enables that, with interchangeable drag and drop between all three types of item widgets. #python #pyside #qt
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rich_drag_and_drop.py
import abc
import json
import inspect
from collections import defaultdict
from typing import Type, Iterable
from functools import partial
from PySide2 import QtWidgets, QtGui, QtCore
class SerializableItemMixin:
"""
This - alongside DragAndDropItemsConverter - allows for the drag and drop of
copies of Qt ____WidgetItems between views while preserving their data types.
If this is used multiple times, each should set its own SerializedTypeID value
to ensure objects are reconstructed correctly. If using multiple ItemWidgets
with the same serializable data types, they can use the same SerializedTypeID
to enable drag and drop between them.
"""
SerializedTypeID = 0
@abc.abstractmethod
def to_serializable(self):
raise NotImplementedError()
@classmethod
@abc.abstractmethod
def from_serializable(cls, data):
raise NotImplementedError()
class SerializableItemManager:
SERIALIZED_MIMETYPE = "/serialized-objects/data/"
SERIALIZED_OBJECT_ID_MIMETYPE = "/serialized-objects/type-id/"
_typeID_itemType_map = defaultdict(lambda: dict())
@classmethod
def addItemsToMimedata(cls, items, mimedata: QtCore.QMimeData):
typeIds = [item.SerializedTypeID for item in items if isinstance(item, SerializableItemMixin)]
mimedata.setData(cls.SERIALIZED_OBJECT_ID_MIMETYPE, cls.serializeData(typeIds))
mimedata.setData(cls.SERIALIZED_MIMETYPE, cls.serializeItems(items))
@classmethod
def getItemsFromMimedata(cls, caller, mimedata: QtCore.QMimeData):
if not (mimedata.hasFormat(cls.SERIALIZED_MIMETYPE) and mimedata.hasFormat(cls.SERIALIZED_OBJECT_ID_MIMETYPE)):
return []
typeIds = cls.deserializeData(mimedata.data(cls.SERIALIZED_OBJECT_ID_MIMETYPE))
object_data = cls.deserializeData(mimedata.data(cls.SERIALIZED_MIMETYPE))
return cls.deserializeItemsFromSerializable(caller, typeIds, object_data)
@classmethod
def serializeItems(cls, items: Iterable[object]):
serializable_data = [item.to_serializable() for item in items if isinstance(item, SerializableItemMixin)]
return cls.serializeData(serializable_data)
@classmethod
def serializeData(cls, serializable_data):
return QtCore.QByteArray(json.dumps(serializable_data).encode())
@classmethod
def deserializeData(cls, serialized: QtCore.QByteArray):
return json.loads(str(serialized.data(), encoding="utf-8"))
@classmethod
def deserializeItemsFromSerializable(cls, caller, typeIds, data):
items = []
for typeId, serialized in zip(typeIds, data):
typeKey = cls.getTypeKey(caller)
item_type: SerializableItemMixin = cls._typeID_itemType_map[typeId].get(typeKey)
if not item_type: continue
items.append(item_type.from_serializable(serialized))
return items
@classmethod
def getTypeKey(cls, caller):
if not inspect.isclass(caller):
caller = caller.__class__
if issubclass(caller, (QtWidgets.QTreeWidget, QtWidgets.QTreeWidgetItem)):
return "tree"
if issubclass(caller, (QtWidgets.QTableWidget, QtWidgets.QTableWidgetItem)):
return "table"
if issubclass(caller, (QtWidgets.QListWidget, QtWidgets.QListWidgetItem)):
return "list"
return None
@classmethod
def registerCustomWidgetItemType(cls, object_type: Type[SerializableItemMixin]):
typeKey = cls.getTypeKey(object_type)
cls._typeID_itemType_map[object_type.SerializedTypeID][typeKey] = object_type
class SerializableListWidget(QtWidgets.QListWidget):
def mimeData(self, items):
data = QtWidgets.QListWidget.mimeData(self, items)
SerializableItemManager.addItemsToMimedata(items, data)
return data
def dropMimeData(self, index:int, data:QtCore.QMimeData, action:QtCore.Qt.DropAction) -> bool:
items = SerializableItemManager.getItemsFromMimedata(self, data)
if items:
for i, item in enumerate(items):
self.insertItem(index+i, item)
return True
else:
return QtWidgets.QListWidget.dropMimeData(self, index, data, action)
class SerializableTreeWidget(QtWidgets.QTreeWidget):
def mimeData(self, items):
data = QtWidgets.QTreeWidget.mimeData(self, items)
SerializableItemManager.addItemsToMimedata(items, data)
return data
def dropMimeData(self, parent:QtWidgets.QTreeWidgetItem, index:int, data:QtCore.QMimeData, action:QtCore.Qt.DropAction) -> bool:
items = SerializableItemManager.getItemsFromMimedata(self, data)
if items:
parent = self.invisibleRootItem() if parent is None else parent
parent.setExpanded(True)
for i, item in enumerate(items):
parent.insertChild(index+i, item)
return True
else:
return QtWidgets.QTreeWidget.dropMimeData(self, parent, index, data, action)
class SerializableTableWidget(QtWidgets.QTableWidget):
def mimeData(self, items):
if not items: return None
data = QtWidgets.QTableWidget.mimeData(self, items)
SerializableItemManager.addItemsToMimedata(items, data)
return data
def dropMimeData(self, row:int, column:int, data:QtCore.QMimeData, action:QtCore.Qt.DropAction) -> bool:
items = SerializableItemManager.getItemsFromMimedata(self, data)
if items:
self.setItem(row, column, items[0])
return True
else:
return QtWidgets.QTableWidget.dropMimeData(self, row, column, data, action)
def make_widget_serializable(widget):
"""
Monkeypatches an existing widget to add handling for the SerializableItemMixin
in its drag and drop functionality. It will overwrite the default mimeData functions.
"""
if isinstance(widget, QtWidgets.QListWidget):
widget.mimeData = partial(SerializableListWidget.mimeData, widget)
widget.dropMimeData = partial(SerializableListWidget.dropMimeData, widget)
elif isinstance(widget, QtWidgets.QTreeWidget):
widget.mimeData = partial(SerializableTreeWidget.mimeData, widget)
widget.dropMimeData = partial(SerializableTreeWidget.dropMimeData, widget)
elif isinstance(widget, QtWidgets.QTableWidget):
widget.mimeData = partial(SerializableTableWidget.mimeData, widget)
widget.dropMimeData = partial(SerializableTableWidget.dropMimeData, widget)
# ----------------------------------------------------------
# Example
class MyDataType:
def __init__(self, name, age):
self.name = name
self.age = age
@classmethod
def from_dictionary(cls, data):
obj = cls(None, None)
obj.__dict__ = data
return obj
def to_dictionary(self):
return self.__dict__
class SerializableMyDataTypeMixin(SerializableItemMixin):
def __init__(self, data):
super(SerializableItemMixin, self).__init__(data)
self.myData = data
def to_serializable(self):
return self.myData.to_dictionary()
@classmethod
def from_serializable(cls, data):
return cls(MyDataType.from_dictionary(data))
class MyDataListWidgetItem(QtWidgets.QListWidgetItem, SerializableMyDataTypeMixin):
def __init__(self, data):
super(MyDataListWidgetItem, self).__init__()
self.myData = data
self.setText(data.name + " - " + str(data.age))
self.setFlags(self.flags() | QtCore.Qt.ItemIsDragEnabled)
SerializableItemManager.registerCustomWidgetItemType(MyDataListWidgetItem)
class MyDataTreeWidgetItem(QtWidgets.QTreeWidgetItem, SerializableMyDataTypeMixin):
def __init__(self, data):
super(MyDataTreeWidgetItem, self).__init__()
self.myData = data
self.setText(0, data.name)
self.setText(1, str(data.age))
self.setFlags(self.flags() | QtCore.Qt.ItemIsDragEnabled)
SerializableItemManager.registerCustomWidgetItemType(MyDataTreeWidgetItem)
class MyDataTableWidgetItem(QtWidgets.QTableWidgetItem, SerializableMyDataTypeMixin):
def __init__(self, data):
super(MyDataTableWidgetItem, self).__init__()
self.myData = data
self.setText(data.name + ", " + str(data.age))
self.setFlags(self.flags() | QtCore.Qt.ItemIsDragEnabled)
SerializableItemManager.registerCustomWidgetItemType(MyDataTableWidgetItem)
class TestDialog(QtWidgets.QDialog):
def __init__(self, a_data, b_data):
super(TestDialog, self).__init__()
self.a_data = a_data
self.b_data = b_data
self.__setupUI()
self.populateLists()
self.__setupCallbacks()
def __setupUI(self):
layout = QtWidgets.QVBoxLayout()
self.setLayout(layout)
self.listWidgetA = QtWidgets.QListWidget()
self.listWidgetA.setDragEnabled(True)
self.listWidgetA.setAcceptDrops(False)
self.listWidgetA.setDragDropMode(QtWidgets.QAbstractItemView.DragOnly)
layout.addWidget(self.listWidgetA)
self.listWidgetB = QtWidgets.QListWidget()
self.listWidgetB.setAcceptDrops(True)
self.listWidgetB.setDragEnabled(True)
self.listWidgetB.setDragDropMode(QtWidgets.QAbstractItemView.DragDrop)
self.listWidgetB.setDefaultDropAction(QtCore.Qt.MoveAction)
layout.addWidget(self.listWidgetB)
self.treeWidgetB = QtWidgets.QTreeWidget()
self.treeWidgetB.setColumnCount(2)
self.treeWidgetB.setHeaderLabels(["name", "age"])
self.treeWidgetB.setAcceptDrops(True)
self.treeWidgetB.setDragEnabled(True)
self.treeWidgetB.setDragDropMode(QtWidgets.QAbstractItemView.DragDrop)
self.treeWidgetB.setDefaultDropAction(QtCore.Qt.MoveAction)
layout.addWidget(self.treeWidgetB)
self.tableWidgetB = QtWidgets.QTableWidget()
self.tableWidgetB.setRowCount(4)
self.tableWidgetB.setColumnCount(4)
self.tableWidgetB.setAcceptDrops(True)
self.tableWidgetB.setDragEnabled(True)
self.tableWidgetB.setDragDropMode(QtWidgets.QAbstractItemView.DragDrop)
self.tableWidgetB.setDefaultDropAction(QtCore.Qt.MoveAction)
layout.addWidget(self.tableWidgetB)
self.testButton = QtWidgets.QPushButton("test!")
layout.addWidget(self.testButton)
self.setWindowFlags(QtCore.Qt.WindowStaysOnTopHint)
make_widget_serializable(self.listWidgetA)
make_widget_serializable(self.listWidgetB)
make_widget_serializable(self.treeWidgetB)
make_widget_serializable(self.tableWidgetB)
def __setupCallbacks(self):
self.testButton.clicked.connect(self.runTest)
def populateLists(self):
self.listWidgetA.clear()
self.listWidgetB.clear()
for data in self.a_data:
item = MyDataListWidgetItem(data)
self.listWidgetA.addItem(item)
self.listWidgetA.addItem(QtWidgets.QListWidgetItem("special case"))
for data in self.b_data:
item = MyDataListWidgetItem(data)
self.listWidgetB.addItem(item)
def runTest(self):
print("testing!")
for i in range(self.listWidgetB.count()):
item = self.listWidgetB.item(i)
print(item)
if __name__ == '__main__':
a_data = [
MyDataType("Mitchell", 24),
MyDataType("Jason", 35),
MyDataType("Bourne", 44),
]
b_data = [
MyDataType("Watney", 29),
]
w = TestDialog(a_data, b_data)
w.show()
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