Hello,
This issue is a regression from emacs 25.x.
I discovered this issue while using multiple-cursors package that uses a dynamic minor mode lighter that shows the active number of multiple cursors.
(defcustom mc/mode-line
`(" mc:" (:eval (format ,(propertize "%d" 'face 'font-lock-warning-face)
(mc/num-cursors))))
"What to display in the mode line while multiple-cursors-mode is active."
:group 'multiple-cursors)
But the issue can be easily recreated using this dummy code:
=====
(defvar test-cache 0)
(defconst test-format-mode-lighter
`(" test:" (:eval (format ,(propertize "%d" 'face 'font-lock-warning-face) (test-incr)))))
(defun test-incr ()
(setq test-cache (1+ test-cache))
test-cache)
(define-minor-mode test-format-mode
"Test that the dynamic minor mode lighter does not get truncated."
:lighter test-format-mode-lighter
(unless test-format-mode
(setq test-cache 0)))
=====
1. Start emacs -Q (emacs 26+).
2. Evaluate the above dummy code snippet.
3. M-x test-format-mode
You will see this:
4. Now move the cursor around.. you will see the number after "test:" increment.. once it reaches 9, the next increment would be 10.. but then the numbers disappear altogether. You see this now:
Upon doing C-h v test-format-mode-lighter, I see:
test-format-mode-lighter’s value is
(" test:"
(:eval
(format
#("%d" 0 2
(face font-lock-warning-face))
(test-incr))))
I don't understand the exact meaning of those numbers "0 2", but looks like that limits the number of characters to be displayed after "test:"?
As a quick hack, I replace the "%d" in that variable with "%-3d".
Now the C-h v gives:
test-format-mode-lighter’s value is
(" test:"
(:eval
(format
#("%-3d" 0 4
(face font-lock-warning-face))
(test-incr))))
So the number of character limit got raised because "%-3d" is literally 4 characters.
If I make that "%-10d".. the limit is literally 5 characters!!
test-format-mode-lighter’s value is
(" test:"
(:eval
(format
#("%-10d" 0 5
(face font-lock-warning-face))
(test-incr))))
This strange truncation behavior did not exist on emacs 25+.
My guess is that the
In GNU Emacs 26.0.60 (build 3, x86_64-pc-linux-gnu, GTK+ Version 2.24.23)
of 2017-09-20
Repository revision: f16a8d5dbd3bb8a319c951bdde9a6a75dbdb8c17
Windowing system distributor 'The X.Org Foundation', version 11.0.60900000
System Description: Red Hat Enterprise Linux Workstation release 6.6 (Santiago)
Recent messages:
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