Two problems:

1. std::map::at is c++11.
2. std::map::at throws an exception if event.key.keysym.scancode is not in the map.  This is not checked for.

Suggest replacing with

```
map<int, int>::const_iterator i = m_keyPadMap.find(event.key.keysym.scancode);
if (i != m_keyPadMap.end())
  number = number*10 + *i;
```