Force redisplay to trigger height calculations

ertain functions, including e.g. `fit-window-to-buffer', base
their size calculations on values that are incorrect if the
mode-line has a height different from that of the `default' face
and certain other calculations have not yet taken place for the
window in question.

Force a redisplay before `fit-window-to-buffer' using an advice,
like we already did for `resize-temp-buffer-window'.

Close #183.

Reference:
https://github.com/tarsius/moody/issues/19
https://github.com/magit/transient/issues/63

doom-modeline-core.el

@@ -125,7 +125,6 @@ It returns a file name which can be used directly as argument of
     ("battery-three-quarters" . "\xf241")))
 (doom-moddeline--set-font-widths doom-modeline-rhs-icons-alist)
 
-
 ;;
 ;; Customizations
 ;;
@@ -612,6 +611,24 @@ It respects `doom-modeline-icon' and `all-the-icons-color-icons'."
 ;; Plugins
 ;;
 
+(defun doom-modeline-redisplay (&rest _)
+  "Call `redisplay' to trigger mode-line height calculations.
+Certain functions, including e.g. `fit-window-to-buffer', base
+their size calculations on values which are incorrect if the
+mode-line has a height different from that of the `default' face
+and certain other calculations have not yet taken place for the
+window in question.
+These calculations can be triggered by calling `redisplay'
+explicitly at the appropriate time and this functions purpose
+is to make it easier to do so.
+This function is like `redisplay' with non-nil FORCE argument.
+It accepts an arbitrary number of arguments making it suitable
+as a `:before' advice for any function."
+  (redisplay t))
+
+(advice-add #'fit-window-to-buffer :before #'doom-modeline-redisplay)
+(advice-add #'resize-temp-buffer-window :before #'doom-modeline-redisplay)
+
 ;; Keep `doom-modeline-current-window' up-to-date
 (defun doom-modeline--get-current-window ()
   "Get the current window but should exclude the child windows."