Force QPlainTextEdit uppercase characters

Question

I want to convert all lowercase characters as I type to uppercase in a QPlainTextEdit. In a QLineEdit I do the same via a validator, but there seems to be no validator for QPlainTextEdit.

I have tried ui->pte_Route->setInputMethodHints(Qt::ImhUppercaseOnly); but it does nothing, most likely using it wrong.

Any better option as using my "own" class?

Answer 1

A quick test using an event filter seems to work reasonably well...

class plain_text_edit: public QPlainTextEdit {
  using super = QPlainTextEdit;
public:
  explicit plain_text_edit (QWidget *parent = nullptr)
    : super(parent)
    {
      installEventFilter(this);
    }
protected:
  virtual bool eventFilter (QObject *obj, QEvent *event) override
    {
      if (event->type() == QEvent::KeyPress) {
        if (auto *e = dynamic_cast<QKeyEvent *>(event)) {

          /*
           * If QKeyEvent::text() returns an empty QString then let normal
           * processing proceed as it may be a control (e.g. cursor movement)
           * key.  Otherwise convert the text to upper case and insert it at
           * the current cursor position.
           */
          if (auto text = e->text(); !text.isEmpty()) {
            insertPlainText(text.toUpper());

            /*
             * return true to prevent further processing.
             */
            return true;
          }
        }
      }
      return super::eventFilter(obj, event);
    }

If it does work sufficiently well then the event filter code can always be pulled out separately for re-use.