Hi, thanks for the update.
I'm pretty new to Qt (and to C++) and I'm having trouble using your project. Running Qt-Creator 3.3.0 and Qt5.4.
I can open your project, but compiling it yields errors.
numpad.cpp:166:18: error: taking the address of a temporary object of type 'QVariant' [-Waddress-of-temporary]
emit dataSet(&QVariant(ui->edValue->text()));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
numpad.cpp:189:33: error: non-const lvalue reference to type 'QString' cannot bind to a temporary of type 'QString'
if (validator->validate(ui->edValue->text(),pos) == QValidator::Acceptable)
^~~~~~~~~~~~~~~~~~~
/Users/srm/Development/Qt/5.4/clang_64/lib/QtGui.framework/Headers/qvalidator.h:67:37: note: passing argument to parameter here
virtual State validate(QString &, int &) const = 0;
^
This was running qmake && make in the project dir.
What am I doing wrong? Do you need any more information?

EDIT: running on OSX 10.10.2