[Interest] QStandardItemModel - Delegate with custom widget

[Dirk Neumann]

Hello,

I know that this is nearly an everlasting topic - place a custom Widget
into a QTreeView.
The widget I want to be displayed is up to now I arranged a QLabel and a
QTextEdit, but in Future the widget will be of higher complexity.
Nevertheless, the widget itself works for me and is called
ReqTextItemWidget.
I derived QStyledItemDelegate and overrode createEditor(),
setEditorData(), setModelData(). All these methods do what I expect,
the data from model will be passed into editor and vice versa, I can
edit data, fine.
I also overrode sizeHint() and paint() of the delegate. My sizeHint
method looks:

QSize ReqTextDelegate::sizeHint(const QStyleOptionViewItem &option,
      const QModelIndex &index) const{
  ReqTextItemWidget *item_widget=new ReqTextItemWidget();
  QString value=index.data().toString();
  item_widget->set_caption("Unicornpolish");
  item_widget->set_maintext(value);
  item_widget->setGeometry(option.rect);
  return item_widget->sizeHint();
}

where set_maintext() sets the text in the QTextEdit and set_caption()
sets the text in the QLabel, just to get a calculated size.
This is my paint()-method:

void ReqTextDelegate::paint(QPainter *painter,const
QStyleOptionViewItem &option, QModelIndex const& index)
const{ QPaintDevice* original_pdev_ptr = painter->device();

  if (option.state & QStyle::State_Selected)
  painter->fillRect(option.rect, option.palette.highlight());
  ReqTextItemWidget *item_widget=new ReqTextItemWidget(); QString
  value=index.data().toString();
  item_widget->set_caption("Unicornpolish");
  item_widget->set_maintext(value);

  // geometry
  item_widget->setGeometry(option.rect);

  painter->end();
  // rendering of QWidget itself
  //region relative to option.rect
  int region_x=-100;  //  ----> value
  int region_y=-25;   //  ----> value
  int region_w=option.rect.width()-region_x;
  int region_h=option.rect.height()-region_y;
  item_widget->render(painter->device(), QPoint(option.rect.x(),
    option.rect.y()), QRegion(region_x, region_y, region_w, region_h),
    QWidget::RenderFlag::DrawChildren);

  painter->begin(original_pdev_ptr);
}

My problem now is the adjustment of the values region_x and region_y
for placing the widget just to the same place as the editor.
But hard coding values are eval. Not portable. No-Go. What can I do
here?

I also played around with setIndexWidget(), but then it seems
that I loose control over the widgets: Selecting and editing in one
widget has nothing to do with the selected item in my QTreeView. I
could catch some signals from the widgets to adjust the selection of
the QTreeView (and maybe can even handle it by using QSignalMapper) but
I fear the moment when I do some changes in the model which change the
tree structure...

Greetings

Dirk.
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