Popup QCompleter in QStyledItemDelegate immediately without text input

Question

I have a QCompleter on a QTableWidget column. As soon as the user starts editing I would like the completer to pop up, not waiting for them to enter text first. I subclassed the setEditorData function of the QStyledItemDelegate to do this which seems to make the most sense to me, however when I call completer.complete() nothing happens until I finish editing (at which point the popup fires).

Here is my code for the delegate:

class CompleterItemDelegate(QtGui.QStyledItemDelegate):
    def createEditor(self, parent, option, index):
        completer = QtGui.QCompleter(['test', 'test2'])
        completer.setCompletionMode(completer.UnfilteredPopupCompletion)

        edit = QtGui.QLineEdit(parent)
        edit.setCompleter(completer)
        return edit

    def setEditorData(self, editor, index):
        completer = editor.completer()
        completer.complete() # does not fire until after editing is done
        completer.popup().show() # no luck here either
        print("setting editor data") # this however does work as expected...
        super().setEditorData(editor, index)

Answer 1

You have to call complete() when the widget is displayed and for this you can use the showEvent() method:

from PyQt4 import QtCore, QtGui


class LineEdit(QtGui.QLineEdit):
    def showEvent(self, event):
        if self.completer() is not None:
            QtCore.QTimer.singleShot(0, self.completer().complete)
        super().showEvent(event)


class CompleterItemDelegate(QtGui.QStyledItemDelegate):
    def createEditor(self, parent, option, index):
        completer = QtGui.QCompleter(["test", "test2"])
        completer.setCompletionMode(QtGui.QCompleter.UnfilteredPopupCompletion)
        edit = LineEdit(parent)
        edit.setCompleter(completer)
        return edit


def main(args):
    app = QtGui.QApplication(args)

    w = QtGui.QTableWidget(4, 4)
    delegate = CompleterItemDelegate(w)
    w.setItemDelegate(delegate)
    w.show()

    ret = app.exec_()
    return ret


if __name__ == "__main__":
    import sys

    sys.exit(main(sys.argv))