QAbstractTableModel does not draw checkbox for checkable items

Comments

• EugeneZelenko

  March 2022

  See https://www.klayout.de/forum/discussion/2047/problem-with-qtreewidgetitem-setbackground as example of CheckState usage in QTreeWidget.
• alexlpn

  March 2022

  Hi @EugeneZelenko, thanks for the comment. I am not sure that understand it completely, but it looks like you are referring to changing check state of particular item in your QTreeWidget, am I right?
  The point is that this is widget based way and it works for me as well (for QTableWidget) but I am trying switching to model-view architecture and check state in this way can be controlled through model directly. As I said, with raw Qt or PyQt I know how to do that but here checkbox is not plotting. Please, correct me if I misinterpreted your message.

  Custom editing elements can be handled through user's delegate class, but for checking items it was always possible to use standard delegate.
• Matthias

  March 2022

  @alexlpn I cannot debug or reproduce that isuee with partial code. Could you paste a full sample that allows me to reproduce the problem?

  The reason may be manifold. I'm not using the Qt classes to an extent I have much experience with that myself.

  A note of caution: the Qt bindings do not have the quality of PyQt, but I could not use PyQt. The reason is that PyQt is build atop of Python while in KLayout, Python sits atop of the application. That is a difference. Plus there was not PyQt equivalent for Ruby. So KLayout's Qt binding is supposed to provide the necessary API for utility UIs, but C++ to Python transition is tricky and I cannot give warranty that all functionality is properly implemented. The Qt API is simply too huge to give it a thorough testing.

  I'd like to debug the issue, but please do not ask me to create a functional sample myself.

  Matthias
• alexlpn

  March 2022

  Hi @Matthias , here I tried to compile small example (actually two).
  This one is raw PyQt5 based:

  from PyQt5.QtCore import QAbstractTableModel, QModelIndex, Qt, QVariant
  from PyQt5.QtWidgets import QApplication, QMainWindow, QTableView
  from dataclasses import dataclass, fields
  from typing import List
  
  
  @dataclass
  class Item:
      name: str
      value: float
      is_checked: bool
  
  
  class Model(QAbstractTableModel):
      def __init__(self):
          super().__init__()
          self.items = []
  
      def setItems(self, items: List[Item]):
          self.items = items
          self.layoutChanged.emit()
  
      def setAllItemsSelected(self, selected: bool = True):
          for r in self.items:
              r.is_checked = selected
          self.layoutChanged.emit()
  
      def rowCount(self, parent=QModelIndex()):
          return len(self.items)
  
      def columnCount(self, parent=QModelIndex()):
          return len(fields(Item)) - 1
  
      def data(self, index, role=Qt.DisplayRole):
          if role == Qt.DisplayRole:
              if index.column() == 0:
                  value = self.items[index.row()].name
              elif index.column() == 1:
                  value = self.items[index.row()].value
              else:
                  value = ""
              return value
          elif role == Qt.CheckStateRole and index.column() == 0:
              return Qt.Checked if self.items[index.row()].is_checked else Qt.Unchecked
          else:
              return QVariant()
  
      def headerData(self, section, orientation, role=Qt.DisplayRole):
          if role == Qt.DisplayRole and orientation == Qt.Horizontal:
              if section == 0:
                  value = "Name"
              elif section == 1:
                  value = "Value"
              else:
                  value = ""
              return value
          elif role == Qt.DisplayRole and orientation == Qt.Vertical:
              return section + 1
  
      def flags(self, index):
          fl = QAbstractTableModel.flags(self, index)
          if index.column() == 0:
              fl |= Qt.ItemIsEditable | Qt.ItemIsUserCheckable
          return fl
  
  
  class MainWindow(QMainWindow):
      def __init__(self, parent=None):
          super().__init__()
          table = QTableView(self)
          model = Model()
          table.setModel(model)
          self.setCentralWidget(table)
  
          items = [
              Item("Item 1", 10.0, False),
              Item("Item 2", 20.0, False),
              Item("Item 3", 30.0, True),
              Item("Item 4", 40.0, True),
              Item("Item 5", 50.0, True),
          ]
  
          model.setItems(items)
  
  
  if __name__ == "__main__":
      app = QApplication([])
      wnd = MainWindow()
      wnd.show()
      app.exec()
  

  This one is pya based (the difference is in Qt.CheckStateRole -> Qt.CheckStateRole.to_i() and similar roles :

  from pya import QAbstractTableModel, QModelIndex, Qt, QVariant
  from pya import QMainWindow, QTableView
  from dataclasses import dataclass, fields
  from typing import List
  
  
  @dataclass
  class Item:
      name: str
      value: float
      is_checked: bool
  
  
  class Model(QAbstractTableModel):
      def __init__(self):
          super().__init__()
          self.items = []
  
      def setItems(self, items: List[Item]):
          self.items = items
          self.emit_layoutChanged()
  
      def setAllItemsSelected(self, selected: bool = True):
          for r in self.items:
              r.is_checked = selected
          self.emit_layoutChanged()
  
      def rowCount(self, parent=QModelIndex()):
          return len(self.items)
  
      def columnCount(self, parent=QModelIndex()):
          return len(fields(Item)) - 1
  
      def data(self, index, role=Qt.DisplayRole):
          if role == Qt.DisplayRole.to_i():
              if index.column() == 0:
                  value = self.items[index.row()].name
              elif index.column() == 1:
                  value = self.items[index.row()].value
              else:
                  value = ""
              return value
          elif role == Qt.CheckStateRole.to_i() and index.column() == 0:
              return Qt.Checked if self.items[index.row()].is_checked else Qt.Unchecked
          else:
              return QVariant()
  
      def headerData(self, section, orientation, role=Qt.DisplayRole):
          if role == Qt.DisplayRole.to_i() and orientation == Qt.Horizontal:
              if section == 0:
                  value = "Name"
              elif section == 1:
                  value = "Value"
              else:
                  value = ""
              return value
          elif role == Qt.DisplayRole.to_i() and orientation == Qt.Vertical:
              return section + 1
  
      def flags(self, index):
          fl = QAbstractTableModel.flags(self, index)
          if index.column() == 0:
              fl |= Qt.ItemIsEditable | Qt.ItemIsUserCheckable
          return fl
  
  
  class MainWindow(QMainWindow):
      def __init__(self, parent=None):
          super().__init__()
          self.table = QTableView(self)
          self.model = Model()
          self.table.setModel(self.model)
          self.setCentralWidget(self.table)
  
          items = [
              Item("Item 1", 10.0, False),
              Item("Item 2", 20.0, False),
              Item("Item 3", 30.0, True),
              Item("Item 4", 40.0, True),
              Item("Item 5", 50.0, True),
          ]
  
          self.model.setItems(items)
  
  
  if __name__ == "__main__":
      wnd = MainWindow()
      wnd.show()
  

  Here are the plots of what gives PyQt and pya in comparison:

  

  

  Those checkboxes I am talking about. Usually when I am flagging item as Qt.ItemIsUserCheckable this delegate will be plotted automatically.
  I hope this highlights the issue.
• Matthias

  April 2022 edited April 2022

  Thanks, a lot for that nice test case.

  I could debug the problem and fix it by using

          elif role == Qt.CheckStateRole.to_i() and index.column() == 0:
              return Qt.Checked.to_i() if self.items[index.row()].is_checked else Qt.Unchecked.to_i()
  

  (note the to_i() in the return statement).

  Here is my explanation: KLayout treats enums as typed objects. So if you have Qt.CheckStateRole it is actually a constant of type Qt::ItemDataRole.

  That usually works nicely, but for the QAbstractItemModel, for some reason the role is declared as "int" in C++. Hence for the comparison you need to convert to int with to_i. Maybe that can be simplified if I implement some "enum == int" compare. Until then you'll need to_i.

  The same thing happens on the return side. The QVariant binding does not support "enum type to int" automatic conversion, but the C++ API requires an integer value. So again, you'll need to convert to int again. Maybe it's also possible to rectify that so eventually code is more compatible with PyQt5. Right now, I suggest the "to_i" workaround.

  Kind regards,

  Matthias
• Matthias

  April 2022

  I have issue a PR which should enable enum-to-int conversion in both directions (https://github.com/KLayout/klayout/pull/1055). This should remove the need for adding to_i. It's a too deep change to go into a minor release, but I'll include it in the next major one.
• alexlpn

  April 2022

  Matthias, this is great, thanks a lot!