GUI doesn't redraw cursor immediately.

Probably, the correct solution to that is to draw the cursor only when the windowing system asks Vim to redraw the screen (like the GTK+3 GUI), not every time Vim thinks it necessary to update simply because the contents of a buffer or the position of the cursor has been changed. After all, you cannot update any part of the screen anyway until after the windowing system asks the client to do so.

There should already be several events which are sufficient for Vim to update the screen smoothly even when the built-in terminal is working there (Rather, more events to come). Nonetheless, that "delay" happens (Actually, that's not delay, although I'm not going to talk about that in further detail here). We first need to look into the reason why that happens before immediately resorting to any brute force means.

At least, IMHO, we should wait for the cursor drawing itself being fixed for the non-GUI version, as too early optimization is bad in general.

Yes, you are right. There are many workaround for updating cursor immediately were over 60 places in code. We should make some common function for each use-case.

• update cursor
• draw cursor immediately
• draw cursor in later
  etc...

Hmm, it's heavy redrawing cursor.