Re: ps-print-buffer-with-faces doesn't use selected frame's background

[Richard Stallman]

    4. start new Emacs session

    5. type: C-h v ps-default-bg RET
       ==>> "#ffffff" (white)

That is quite strange, because when I do emacs -Q and 
C-h v ps-default-bg RET it says that variable isn't defined.

I wonder, have you done something to cause ps-print to be preloaded?

    2. set in emacs/lisp/ps-print.el file:
       (defcustom ps-default-bg (frame-parameter nil 'background-color))

Please try this:

       (defcustom ps-default-bg (progn (debug) (frame-parameter nil 
'background-color)))

Then you will go into the debugger when that initialization gets run,
and you can see when it gets done, and what code runs it.

    >     If the variables have a value (let's say, 'frame-parameter), the 
value 
    >     of them is calculated when any ps-print command is activated. And 
it's 
    >     used frame-parameter function to get the color value.
    >

With your explanation, I now understand that idea, and I think it is a
good one.