fix: fill missing env dimension from stty size

When only COLUMNS or only LINES is set, run 'stty size' to get the
other dimension. This handles tmux/screen where only one env var
is exported.

src/backend/modern.lisp

@@ -180,6 +180,18 @@ as a fallback when a keyword is not in *named-colors*.")
                (rstr (sb-ext:posix-getenv "LINES"))
                (cols (when cstr (parse-integer cstr :junk-allowed t)))
                (rows (when rstr (parse-integer rstr :junk-allowed t))))
+          ;; If only one env var is set, get the other from stty
+          (unless (and cols rows)
+            (let* ((out (uiop:run-program '("stty" "size")
+                                          :output :string
+                                          :ignore-error-status t))
+                   (parts (and out (uiop:split-string
+                                     (string-trim '(#\newline #\space) out)))))
+              (when (and parts (= (length parts) 2))
+                (let ((a (parse-integer (first parts) :junk-allowed t))
+                      (b (parse-integer (second parts) :junk-allowed t)))
+                  (when (and a b (> a 0) (> b 0))
+                    (if cols (setf rows b) (setf cols a)))))))
           (when (and cols rows (> cols 0) (> rows 0))
             (values cols rows))))
       (values 80 24)))

src/backend/simple.lisp

@@ -39,6 +39,17 @@
                (rstr (sb-ext:posix-getenv "LINES"))
                (cols (when cstr (parse-integer cstr :junk-allowed t)))
                (rows (when rstr (parse-integer rstr :junk-allowed t))))
+          (unless (and cols rows)
+            (let* ((out (uiop:run-program '("stty" "size")
+                                          :output :string
+                                          :ignore-error-status t))
+                   (parts (and out (uiop:split-string
+                                     (string-trim '(#\newline #\space) out)))))
+              (when (and parts (= (length parts) 2))
+                (let ((a (parse-integer (first parts) :junk-allowed t))
+                      (b (parse-integer (second parts) :junk-allowed t)))
+                  (when (and a b (> a 0) (> b 0))
+                    (if cols (setf rows b) (setf cols a)))))))
           (when (and cols rows (> cols 0) (> rows 0))
             (values cols rows))))
       (values 80 24)))