How to initiate a form based on QUiLoader

[Lykurg]

As I see it, all needed widgets are created on the heap, only the builder is created on the stack. Which is fine.
But are you sure the path to the ui file is correct? I don't think so. Debug what

file.open(QFile::ReadOnly);

file.open(QFile::ReadOnly);

To copy to clipboard, switch view to plain text mode 

says. Remember the relative path is relativ to the executable directory.