Change Details

[] Use `_p.h` name prefix for internal headers [] Unexport internal classes [] Use d-ptr for all exported classes

[x] Use `_p.h` name prefix for internal headers [x] Unexport internal classes [x] Use d-ptr for all exported classes

[x] Use `_p.h` name prefix for internal headers [x] Unexport internal classes [x] Use d-ptr for all exported classes