Between the braces of SINGAL() and SLOT() should be no spaces unless absolutely required (i.e. in `const foo` you cannot avoid the space, but most of the time the `const` is superfluous).

These are actually strings that have to be stripped off their spaces before they can be compared; which is a memory and time overhead that is simply not necessary. Also, this is the cause why namespaces must always be fully qualified in definition and usage of slots and signals...