Keeping context while scrolling

Question

Suppose I have a very long file, for example:

class X {
    // ...
    void foo() {
        // ...
        if (something) {
            a00();
            a01();
            a02();
            // ...
            // ...
            a98();
            a99();
        }
    }
}

When scrolling down to the bottom, all the context (ie., class X, void foo, if (something)) is invisible simply because its outside the current view:

            a93();
            a94();
            a95();
            a96();
            a97();
            a98();
            a99();
        }
    }
}

Is there any way to make vim keep the current context, ie, display something like this:

class X {                    <C>
    void foo() {             <C>
        if (something) {     <C>
            a96();
            a97();
            a98();
            a99();
        }
    }
}

with some markings (<C> in my example) to denote that the lines above a96 are not directly preceding the next one?

Answer 1

I would simply use :rightbelow split.

Answer 2

There is a plugin for that here. I've checked it and it works with Vim8, although plugin was written for Vim6. It opens a window above and updates it on CursorHold event. It's supposed to work only with C files, but adding line:

au CursorHold  *.[cC][pP][pP] call <SID>cursorhold()

right after line 431 makes it work with C++ files as well.

EDIT: I've managed to update the script to include C++ classes (and it should work with Pike programming language f.ex. as well). I'll update it a bit more later on. Updated version can be found here