Use window-full-width-p instead of comparing frame-width and

window-width.

lisp/calendar/calendar.el

@@ -2078,7 +2078,7 @@ Or, for optional MON, YR."
     ;; Don't do any window-related stuff if we weren't called from a
     ;; window displaying the calendar
     (when in-calendar-window
-      (if (or (one-window-p t) (/= (frame-width) (window-width)))
+      (if (or (one-window-p t) (not (window-full-width-p)))
           ;; Don't mess with the window size, but ensure that the first
           ;; line is fully visible
           (set-window-vscroll nil 0)

lisp/dired.el

@@ -2547,12 +2547,12 @@ deletion of non-empty directories is allowed."
       (cond ;; if split-height-threshold is enabled, use the largest window
             ((and (> (window-height (setq w2 (get-largest-window)))
 		     split-height-threshold)
-		  (= (frame-width) (window-width w2)))
+		  (window-full-width-p w2))
 	     (setq window w2))
 	    ;; if the least-recently-used window is big enough, use it
 	    ((and (> (window-height (setq w2 (get-lru-window)))
 		     (* 2 window-min-height))
-		  (= (frame-width) (window-width w2)))
+		  (window-full-width-p w2))
 	     (setq window w2)))
       (save-excursion
 	(set-buffer buf)

lisp/mouse-drag.el

@@ -158,7 +158,7 @@ Keep the cursor on the screen as needed."
 Basically, we check for existing horizontal scrolling."
   (or truncate-lines
       (> (window-hscroll (selected-window)) 0)
-      (< (window-width) (frame-width))
+      (not (window-full-width-p))
       (and
        mouse-drag-electric-col-scrolling
        (save-excursion  ;; on a long line?