fix: revert to simple ioctl-first with env var fallback

The previous logic (check ioctl result, prefer env when 80x24)
added complexity and crashes. Simple or with env vars after ioctl
is safe: ioctl returns 80x24 on stdout fd mismatch, env vars
(COLUMNS/LINES from shell) provide the correct initial size.

src/backend/modern.lisp

@@ -164,7 +164,6 @@ as a fallback when a keyword is not in *named-colors*.")
   (values))
 
 (defmethod backend-size ((b modern-backend))
-  (multiple-value-bind (w h)
   (or (ignore-errors
         (let* ((+tiocgwinsz+ 21523)  ; 0x5413 on Linux
                (winsize (sb-alien:make-alien sb-alien:unsigned-short 4)))
@@ -176,31 +175,16 @@ as a fallback when a keyword is not in *named-colors*.")
                  (values (sb-alien:deref winsize 1)  ;; cols
                          (sb-alien:deref winsize 0))) ;; rows
             (sb-alien:free-alien winsize))))
-          (values 0 0))
+      ;; $COLUMNS/$LINES fallback — some systems don't update the
-    ;; If ioctl returned a plausible size (not the 80x24 default),
+      ;; TTY size via ioctl on stdout's fd.
-    ;; trust it — it will be correct at runtime after SIGWINCH.
+      (ignore-errors
-    (if (and (> w 80) (> h 24))
-        (values w h)
-        ;; ioctl returned 80x24 or less — suspicious.  Try $COLUMNS/
-        ;; $LINES from the shell, which reflect the true size at
-        ;; process start even when ioctl on stdout's fd disagrees.
-        (or (ignore-errors
         (let* ((cstr (sb-ext:posix-getenv "COLUMNS"))
                (rstr (sb-ext:posix-getenv "LINES"))
                (cols (when cstr (parse-integer cstr :junk-allowed t)))
                (rows (when rstr (parse-integer rstr :junk-allowed t))))
-                ;; Some environments set only COLUMNS or only LINES.
-                ;; If one is missing, try the other from stty.
-                (when (and cols (null rows))
-                  (let* ((out (uiop:run-program '("stty" "size")
-                                                 :output :string
-                                                 :ignore-error-status t))
-                         (parts (when out (uiop:split-string (string-trim '(#\newline #\space) out)))))
-                    (setf rows (when (and parts (= (length parts) 2))
-                                 (parse-integer (second parts) :junk-allowed t)))))
           (when (and cols rows (> cols 0) (> rows 0))
             (values cols rows))))
-            (values w h)))))
+      (values 80 24)))
 
 (defmethod backend-write ((b modern-backend) string)
   (let ((stream (backend-output-stream b)))

src/backend/simple.lisp

@@ -27,7 +27,6 @@
   (values))
 
 (defmethod backend-size ((b simple-backend))
-  (multiple-value-bind (w h)
   (or (ignore-errors
         (let* ((+tiocgwinsz+ 21523)
                (winsize (sb-alien:make-alien sb-alien:unsigned-short 4)))
@@ -40,24 +39,15 @@
                  (values (sb-alien:deref winsize 1)
                          (sb-alien:deref winsize 0)))
             (sb-alien:free-alien winsize))))
-          (values 0 0))
+      ;; $COLUMNS/$LINES fallback
-    (if (and (> w 80) (> h 24))
+      (ignore-errors
-        (values w h)
-        (or (ignore-errors
         (let* ((cstr (sb-ext:posix-getenv "COLUMNS"))
                (rstr (sb-ext:posix-getenv "LINES"))
                (cols (when cstr (parse-integer cstr :junk-allowed t)))
                (rows (when rstr (parse-integer rstr :junk-allowed t))))
-                (when (and cols (null rows))
-                  (let* ((out (uiop:run-program '("stty" "size")
-                                                 :output :string
-                                                 :ignore-error-status t))
-                         (parts (when out (uiop:split-string (string-trim '(#\newline #\space) out)))))
-                    (setf rows (when (and parts (= (length parts) 2))
-                                 (parse-integer (second parts) :junk-allowed t)))))
           (when (and cols rows (> cols 0) (> rows 0))
             (values cols rows))))
-            (values w h)))))
+      (values 80 24)))
 
 (defmethod backend-write ((b simple-backend) string)
   (let ((stream (backend-output-stream b)))