Mixed language projects (D and C++)

[Preetpal]

I want to reuse existing C++ code in a new project that I am 
writing in D and I want to use D in an existing C++ code base (it 
is not large). I do not anticipate interop being an issue.

I am wondering if mixing D and C++ is a common practice? If it is 
a common practice, is anyone is currently doing this in an open 
source project that I can use as a reference to learn from.

I am also looking to choose a build system that has IDE support 
(I use Emacs but I want to be able to use tooling with support 
for auto-completion). I have used CMake in the past for a couple 
of C++ projects but I do not want to use it for D projects if it 
is not commonly used or supported. The C++ project I have written 
is currently built using Rake (it is basically a Ruby library 
that allows you to write Makefiles in Ruby). All of my D projects 
have basically been single file projects so far.

This is my first post on this forum so I want to introduce 
myself. I am new to the D programming language (I have been using 
it for about a month for minor projects). I replaced an 
AutoHotKey script using the Windows API that I was using for 
maximizing Windows across multiple monitors on Windows 10. I also 
used D lang for processing data (converted data for use in 
another script, checked data invariants) for commercial purposes.