How do I emulate a keypress inside a Vim function?

Question

I'll start with code

function BigScrollUp()
  let count = 20
  while count > 0
    "Press" CTRL-Y <-- how do I emulate this?
    sleep 5m
    count -= 1
  endwhile
endfunction

I want to create a function to quickly scroll up and down, with animation so that I can keep track of where I am going.

Solution 1

Try this:

" Press CTRL-Y:
normal <Ctrl+v><Ctrl+y>

Literally type ctrl+v, followed by ctrl+y which will result in a single character shown as ^Y in your script.

Solution 2

You can use feedkeys(). Type :help feedkeys to read more:

feedkeys({string} [, {mode}])               *feedkeys()*
        Characters in {string} are queued for processing as if they
        come from a mapping or were typed by the user.  They are added
        to the end of the typeahead buffer, thus if a mapping is still
        being executed these characters come after them.
        The function does not wait for processing of keys contained in
        {string}.
        To include special keys into {string}, use double-quotes
        and "\..." notation |expr-quote|. For example,
        feedkeys("\<CR>") simulates pressing of the <Enter> key. But
        feedkeys('\<CR>') pushes 5 characters.
        If {mode} is absent, keys are remapped.
        {mode} is a String, which can contain these character flags:
        'm' Remap keys. This is default.
        'n' Do not remap keys.
        't' Handle keys as if typed; otherwise they are handled as
            if coming from a mapping.  This matters for undo,
            opening folds, etc.
        Return value is always 0.

---

call feedkeys("\<C-Y>")