Qt - update view size on delegate sizeHint change

Question

I have a QTreeView with a QStyledItemDelegate inside of it. When a certain action occurs to the delegate, its size is supposed to change. However I haven't figured out how to get the QTreeView's rows to resize in response to the delegate's editor size changing. I tried QTreeView.updateGeometry and QTreeView.repaint and a couple other things but it doesn't seem to work. Could someone point me in the right direction?

Here's a minimal reproduction (note: The code is hacky in a few places, it's just meant to be a demonstration of the problem, not a demonstration of good MVC).

Steps:

• Run the code below
• Press either "Add a label" button
• Note that the height of the row in the QTreeView does not change no matter how many times either button is clicked.

from PySide2 import QtCore, QtWidgets


_VALUE = 100


class _Clicker(QtWidgets.QWidget):

    clicked = QtCore.Signal()

    def __init__(self, parent=None):
        super(_Clicker, self).__init__(parent=parent)

        self.setLayout(QtWidgets.QVBoxLayout())

        self._button = QtWidgets.QPushButton("Add a label")
        self.layout().addWidget(self._button)

        self._button.clicked.connect(self._add_label)
        self._button.clicked.connect(self.clicked.emit)

    def _add_label(self):
        global _VALUE

        _VALUE += 10

        self.layout().addWidget(QtWidgets.QLabel("Add a label"))

        self.updateGeometry()  # Note: I didn't expect this to work but added it regardless


class _Delegate(QtWidgets.QStyledItemDelegate):
    def createEditor(self, parent, option, index):
        widget = _Clicker(parent=parent)
        viewer = self.parent()

        widget.clicked.connect(viewer.updateGeometries)  # Note: I expected this to work

        return widget

    def paint(self, painter, option, index):
        super(_Delegate, self).paint(painter, option, index)

        viewer = self.parent()

        if not viewer.isPersistentEditorOpen(index):
            viewer.openPersistentEditor(index)

    def setEditorData(self, editor, index):
        pass

    def updateEditorGeometry(self, editor, option, index):
        editor.setGeometry(option.rect)

    def sizeHint(self, option, index):
        hint = index.data(QtCore.Qt.SizeHintRole)

        if hint:
            return hint

        return super(_Delegate, self).sizeHint(option, index)


class _Model(QtCore.QAbstractItemModel):
    def __init__(self, parent=None):
        super(_Model, self).__init__(parent=parent)

        self._labels = ["foo", "bar"]

    def columnCount(self, parent=QtCore.QModelIndex()):
        return 1

    def data(self, index, role):
        if role == QtCore.Qt.SizeHintRole:
            return QtCore.QSize(200, _VALUE)

        if role != QtCore.Qt.DisplayRole:
            return None

        return self._labels[index.row()]

    def index(self, row, column, parent=QtCore.QModelIndex()):
        child = self._labels[row]

        return self.createIndex(row, column, child)

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

    def rowCount(self, parent=QtCore.QModelIndex()):
        if parent.isValid():
            return 0

        return len(self._labels)


application = QtWidgets.QApplication([])

view = QtWidgets.QTreeView()
view.setModel(_Model())
view.setItemDelegate(_Delegate(parent=view))
view.show()

application.exec_()

How do I get a single row in a QTreeView, which has a persistent editor applied already to it, to tell Qt to resize in response to some change in the editor?

Note: One possible solution would be to close the persistent editor and re-open it to force Qt to redraw the editor widget. This would be generally very slow and not work in my specific situation. Keeping the same persistent editor is important.