During idle time with run-with-idle-timer I parse text around a point and update header-line-format.
Unfortunately I can't see update to header line unless I type any key. So I should trigger redisplay.
With (redisplay) header line isn't updated. With (force-window-update) it is updated.
I am not sure what function is appropriated for my usage scenario. There are also redraw-frame and redraw-display and possibly many others.
What function is more efficient in performance?