Performance : QLineEdit first typed caracters appear with approx 1s delay

Hello,

I created a new project with a QMainWindow.
I just added a QLineEdit (horizontal layout = fullwidth); and compiled into release.

The first letters I type in the application appears with a delay of 1 second, then it reacts normally and keyboard input doesn't lag anymore. There seem to be a slow keyboard lazy initialization phase.

I am quite surprised: usually Qt is really fast, I don't understand.