copy string from text box

[jpn]

What did you try so far? And what is a "text box"? QLineEdit? QTextEdit? QTextBrowser? ...

// line edit
lineEdit2->setText(lineEdit1->text());
 
// text edit
textEdit2->setPlainText(textEdit1->toPlainText());

// line edit
lineEdit2->setText(lineEdit1->text());

// text edit
textEdit2->setPlainText(textEdit1->toPlainText());

To copy to clipboard, switch view to plain text mode 

PS. QLineEdit offers a signal returnPressed().