It is a detail, but it would be a nice improvment if one could have tooltip text with TGNumberEntry. What is your opinion?
It is already possible to have tooltip text for the number entry, i.e. :
fNumber->GetNumberEntry()->SetToolTipText("Whatever text you want to see here...");
fNumber->GetButtonUp()->SetToolTipText("Press up to increase the value...");
fNumber->GetButtonDown()->SetToolTipText("Press down to decrease the value...");
Nice! You should perhaps document this nice but hidden feature.