It seems that Emacs 26 just won't create frames at the size I ask for.
The initial frame comes out one column two wide; subsequent
frames (after a short initial delay which I still don't understand) come
out three columns too narrow. The initial divvy still doesn't work
properly. But things are mostly right.
;; Default frame size.
(setq frame-background-mode (if mdw-black-background 'dark 'light)
+ frame-inhibit-implied-resize t
default-frame-alist
`((width . ,(+ mdw-column-width
- (if (>= emacs-major-version 21) 0 1)))
+ (cond ((<= emacs-major-version 20) 1)
+ ((= emacs-major-version 26) 3)
+ (t 0))))
(height . 33)
(vertical-scroll-bars . right)
(cursor-type . bar)
emacs24) e_hextra=5 e_cextra=-6 e_vextra=42 ;;
emacs23-lucid) e_hextra=7 e_cextra=-6 e_vextra=48 ;;
emacs24-lucid) e_hextra=7 e_cextra=-5 e_vextra=48 ;;
+ emacs26-lucid) e_hextra=5 e_cextra=-6 e_vextra=51 ;;
esac
e_colwd=$(( e_colsz*e_charwd + e_colextra ))
e_colchars=$(( e_colsz + e_colextrachars ))