The obvious reason to use QDoubleValidator as a Validator for a QLineEdit is to prevent a later QLineEdit.text().toDouble() to fail.

However .toDouble() seems to accept white space in front and back of a double value in the QString().

The restriction of no spaces in front or back of a double value in the QDoubleValidator limits the usage of a QLineEdit during Copy/Paste procedures.
Sometime you might copy a double value from a source text, but not clicking exactly with the mouse or usage a software that extracts a space around a double-clicked double value you have ' 123.12345 ' in your clipboard.

It is not possible to paste this into the QLineEdit with a QDoubleValidator attached.

Maybe a fixup() that reduces the spaces and reduces the number of digits would be nice.