Drag and drop in itemviews occasionally crashes

[pathmann]

Occasionally (can't reproduce it) the hosting app will crash when starting to drag an item in any itemview.

The reason seems to be a call to mimeTypes in the PythonQtShell implementation of the model.

Script to reproduce this:

from PythonQt.QtCore import Qt, QMimeData
from PythonQt.QtGui import QTreeView, QStandardItemModel, QStandardItem, QAbstractItemView

class mymodel(QStandardItemModel):
    def __init__(self, rows, cols, parent=None):
        super().__init__(rows, cols, parent)

        self.mimecache = []

    def flags(self, index):
        default = Qt.ItemIsSelectable | Qt.ItemIsEnabled

        if index.isValid():
            return default | Qt.ItemIsDragEnabled | Qt.ItemIsDropEnabled
        else:
            return default

    def mimeTypes(self):
        return ["text/plain"]

    def supportedDropActions(self):
        return Qt.MoveAction

    def mimeData(self, indexes):
        try:
            mimedata = QMimeData()
            mimedata.setText(" ".join(map(lambda x: x.data(), indexes)))
            self.mimecache.append(mimedata) #we have to keep this in scope!

            return mimedata
        except Exception as e:
            return 0

    def canDropMimeData(self, mimedata, action, row, column, parent):
        if not mimedata.hasText() or not parent.isValid() or not action & self.supportedDropActions() or row != -1:
            return False

        return True

    def dropMimeData(self, mimedata, action, row, column, parent):
        if action != Qt.MoveAction:
            return False

        if not mimedata.hasText():
            return False

        if mimedata.text() == "":
            return True

        paritem = self.itemFromIndex(parent)
        nitem = QStandardItem(mimedata.text())
        paritem.appendRow(nitem)

        return True


tv = QTreeView(None)
tv.setAttribute(Qt.WA_DeleteOnClose)

model = mymodel(4, 0, tv)
for row in range(4):
    model.setItem(row, 0, QStandardItem("%s" % row))


tv.setDragEnabled(True)
tv.setDropIndicatorShown(True)
tv.setDragDropMode(QAbstractItemView.InternalMove)
tv.setModel(model)
tv.show()

[pathmann]

bfdcbbb fixes the crash, but it's a little bit dirty. Has to work, as long as we don't find the ultimate reason and a fix for it.

[pathmann]

Maybe changing the implementation of every Q*Model::mimeTypes to not use returnValue in PythonQtConv::ConvertPythonToQt is less hacky?

(See https://github.com/pathmann/PythonQt/blob/patched-6/generated_cpp/com_trolltech_qt_gui/com_trolltech_qt_gui7.cpp#L11676 for example)