Is there a autocmd for scrolling a window without moving a cursor, the one that occurs for CTRL+E/Y? Is there some autocmd that is triggered for that? I googled but found nothing.
If you have a look at
:h autocommand-events you will see all events triggered.
There is no autocommand that I see for scrolling without cursor moving.
If you want to add extra functionalities to
<C-y> you can always remap them:
nnoremap <C-E> :echo 'a'<CR> | norm <C-E>