QLineEdit does not handle composed characters correctly on Mac.
Click on a QLineEdit so that is has the focus and press '^{' on the keyboard. The '}' symbol is drawn in the QLineEdit and the cursor stops blinking to inform the user a second key is expected to be pressed to draw the final character. At this stage, click somewhere else so that the QLineEdit loose its focus. The '^{' symbol is still visible. Click again on the QLineEdit: the '}' symbol is still here and cannot be erased.

The '^' should be cleared when the QLineEdit looses its focus because the user has aborted the writing of the composed character.