Locking an org-timer into the mode-line

Question

Context. I frequently use

1. org-mode timers
2. The org-mode clock (which just displays the clock in the org-mode mode-line)
3. A custom "target time" clock, which shows a point in time (either a few minutes or a few hours from now) that I'm trying to get something done by

Here's the way it looks now as an example:

12:40PM 0.57 is the current time, <0:00:42> is the active timer, and 12:48PM is the "target time" I'm trying to get my current task done by.

Problem. This mode-line disappears or gets mangled all of the time (particularly, I think, when I switch buffers around?). I would like it to be displayed universally no matter which emacs buffer I'm in. I've tried setting

(setq global-mode-string '("" display-time-string org-mode-line-string org-timer-mode-line-string " " est-target))  

where est-target is my "target time" (as described in (3)), but it doesn't always work (even when I bind it to key and press it on the current buffer).

Does anyone know how to lock this mode-line in place?

Answer 1

You can set the mode line to be fixed with

(setq-default mode-line-format "FOO")

It will always show "FOO" and nothing else.

I assume that if you do

(setq-default mode-line-format  '("" display-time-string org-mode-line-string org-timer-mode-line-string " " est-target))

and enable things appropriately (e.g. you have to call (display-time) to have display-time-string show anything) you will get what you want.

BUT: the mode line contains all sorts of useful information that you would lose this way.

There is another possibility and that is the header line: it is used occasionally, but not nearly as much as the mode line, so it should be safer to muck around with it. Basically do the same thing but with header-line-format:

(setq-default header-line-format '("" display-time-string org-mode-line-string org-timer-mode-line-string " " est-target))

Maybe that will not be interfered with as much.

Note BTW, that both mode-line-format and header-line-format become buffer-local when set, so using setq only sets the buffer-local-variable. setq-default sets the global value, which is used to initialize the buffer-local variable. Modifying the buffer-local variable by adding things to it but not clobbering it completely should then behave more or less as you expect.

But I have not tested any of this to any extent, so no guarantees: if it breaks, you get to keep the pieces. I would experiment on a session of emacs created for the purpose, not on my main session.