#include <QApplication>
#include <QVBoxLayout>
#include <QPlainTextEdit>
#include <QDialog>
#include <QMessageBox>
#include <QTimer>
#include <QShortcut>

class MyEdit : public QPlainTextEdit
{
public:
	void keyPressEvent(QKeyEvent *e)
	{
		viewport()->setCursor(Qt::BlankCursor);
		QPlainTextEdit::keyPressEvent(e);
	}
};

int main(int argc, char *argv[])
{
	QApplication a(argc, argv);

	QDialog dlg;
	dlg.setLayout(new QVBoxLayout);
	auto edit = new MyEdit;
	dlg.layout()->addWidget(edit);
	dlg.resize(400, 300);

	QShortcut sc(Qt::ALT | Qt::Key_G, &dlg);
	QObject::connect(&sc, &QShortcut::activated, [&]() {
		auto newEdit = new MyEdit;
		QApplication::setOverrideCursor(Qt::BusyCursor);
		dlg.layout()->replaceWidget(edit, newEdit);
		edit = newEdit;
		QEventLoop loop;
		QTimer timer;
		QObject::connect(&timer, &QTimer::timeout, &loop, &QEventLoop::quit);
		timer.start(500);
		loop.exec(QEventLoop::ExcludeUserInputEvents);
		QApplication::restoreOverrideCursor();
	});

	dlg.show();
	return a.exec();
}