fix: ioctl on stdin fd (0) first, then stdout fd, then env vars

The user's terminal reports 186x60 via stty (which uses stdin fd)
and via COLUMNS/LINES, but ioctl on stdout's fd returns 80x24.
Priority: fd 0 → backend output fd → env vars → 80x24 fallback.

src/backend/modern.lisp

@@ -164,19 +164,22 @@ as a fallback when a keyword is not in *named-colors*.")
   (values))
 
 (defmethod backend-size ((b modern-backend))
-  (or (ignore-errors
+  (flet ((ioctl-size (fd)
            (let* ((+tiocgwinsz+ 21523)  ; 0x5413 on Linux
                   (winsize (sb-alien:make-alien sb-alien:unsigned-short 4)))
              (unwind-protect
                   (progn
-                 (sb-unix:unix-ioctl (sb-sys:fd-stream-fd (backend-output-stream b))
+                    (sb-unix:unix-ioctl fd +tiocgwinsz+
-                                     +tiocgwinsz+
                                         (sb-alien:alien-sap winsize))
                     (values (sb-alien:deref winsize 1)  ;; cols
                             (sb-alien:deref winsize 0))) ;; rows
-            (sb-alien:free-alien winsize))))
+               (sb-alien:free-alien winsize)))))
-      ;; $COLUMNS/$LINES fallback — some systems don't update the
+    (or ;; Try ioctl on fd 0 first (stdin — stty uses this)
-      ;; TTY size via ioctl on stdout's fd.
+        (ignore-errors (ioctl-size 0))
+        ;; Then try the output stream's fd
+        (ignore-errors
+          (ioctl-size (sb-sys:fd-stream-fd (backend-output-stream b))))
+        ;; $COLUMNS/$LINES fallback — set by every POSIX shell
         (ignore-errors
           (let* ((cstr (sb-ext:posix-getenv "COLUMNS"))
                  (rstr (sb-ext:posix-getenv "LINES"))
@@ -184,7 +187,7 @@ as a fallback when a keyword is not in *named-colors*.")
                  (rows (when rstr (parse-integer rstr :junk-allowed t))))
             (when (and cols rows (> cols 0) (> rows 0))
               (values cols rows))))
-      (values 80 24)))
+        (values 80 24))))
 
 (defmethod backend-write ((b modern-backend) string)
   (let ((stream (backend-output-stream b)))

src/backend/simple.lisp

@@ -27,19 +27,19 @@
   (values))
 
 (defmethod backend-size ((b simple-backend))
-  (or (ignore-errors
+  (flet ((ioctl-size (fd)
            (let* ((+tiocgwinsz+ 21523)
                   (winsize (sb-alien:make-alien sb-alien:unsigned-short 4)))
              (unwind-protect
                   (progn
-                 (sb-unix:unix-ioctl (sb-sys:fd-stream-fd
+                    (sb-unix:unix-ioctl fd +tiocgwinsz+
-                                      (backend-output-stream b))
-                                     +tiocgwinsz+
                                         (sb-alien:alien-sap winsize))
                     (values (sb-alien:deref winsize 1)
                             (sb-alien:deref winsize 0)))
-            (sb-alien:free-alien winsize))))
+               (sb-alien:free-alien winsize)))))
-      ;; $COLUMNS/$LINES fallback
+    (or (ignore-errors (ioctl-size 0))
+        (ignore-errors
+          (ioctl-size (sb-sys:fd-stream-fd (backend-output-stream b))))
         (ignore-errors
           (let* ((cstr (sb-ext:posix-getenv "COLUMNS"))
                  (rstr (sb-ext:posix-getenv "LINES"))
@@ -47,7 +47,7 @@
                  (rows (when rstr (parse-integer rstr :junk-allowed t))))
             (when (and cols rows (> cols 0) (> rows 0))
               (values cols rows))))
-      (values 80 24)))
+        (values 80 24))))
 
 (defmethod backend-write ((b simple-backend) string)
   (let ((stream (backend-output-stream b)))