how to remove the red area that i think related to trailing spaces
CAVEAT: Deleting the trailing whitespace may have unintended consequences; e.g., there might be a function somewhere containing a regexp to locate a date and that regexp might include trailing spaces
"[0-9]+\s+". If a problem arises, it will be necessary to either remove this
advice or deal with the functions that are at issue. Your mileage with this
advice may vary.
(defun my-function (month year indent) (delete-trailing-whitespace)) (advice-add 'calendar-generate-month :after 'my-function)