fix: add CSI positioning and ioctl sizing to simple-backend

- backend-size now uses TIOCGWINSZ ioctl (like modern-backend)
- draw-text adds \033[row;colH CSI cursor positioning
- draw-rect fills background with space characters at position
- draw-border uses CSI positioning instead of raw newlines+spaces
- Added cursor-hide/cursor-show, cursor-move, initialize/shutdown
- Detection: broader DA1 check (any ANSI response, not just kitty)
- Detection: added TERM-based fallback for modern terminal detection

src/backend/detection.lisp

@@ -31,13 +31,26 @@ TIMEOUT seconds. Returns the response string, or nil if no response."
       response)))
 
 (defun detect-backend-by-da1 ()
-  "Send DA1 (ESC[c) query and check for kitty terminal response code.
-Returns T if terminal reports kitty compatibility codes."
+  "Send DA1 (ESC[c) query and check for any terminal response.
+Returns T if the terminal responds to DA1 (indicating an ANSI-compatible terminal)."
   (let ((response (query-terminal (format nil "~C[c" (code-char 27)))))
     (when response
-      ;; DA1 response format: ESC [ ? digits ; digits c
-      ;; Kitty reports code 62 in the response
-      (search "?62" response))))
+      ;; Any DA1 response (ESC [ ? digits ... c) means the terminal
+      ;; understands ANSI escape sequences — good enough for modern-backend
+      (> (length response) 0))))
+
+(defun detect-backend-by-term ()
+  "Check TERM environment variable for modern terminal types.
+Returns :modern if TERM contains xterm, tmux, screen, kitty,
+alacritty, foot, wezterm, or ghostty."
+  (let ((term (sb-ext:posix-getenv "TERM")))
+    (when term
+      ;; Known non-modern terms
+      (unless (or (string-equal term "dumb")
+                  (string-equal term "dump")
+                  (string-equal term "emacs")
+                  (search "52" term))  ; VT52 — no ANSI
+        :modern))))
 
 (defun detect-backend ()
   "Auto-detect the appropriate backend for the current terminal.
@@ -47,6 +60,7 @@ Result is cached in *detected-backend* for subsequent calls."
       (setf *detected-backend*
             (if (and (detect-backend-by-tty)
                      (or (eql (detect-backend-by-env) :modern)
-                         (detect-backend-by-da1)))
+                         (detect-backend-by-da1)
+                         (eql (detect-backend-by-term) :modern)))
                 (make-modern-backend)
                 (make-simple-backend)))))

src/backend/simple.lisp

@@ -10,20 +10,36 @@
     :output-stream (or output-stream *standard-output*)))
 
 (defmethod initialize-backend ((b simple-backend))
+  (backend-write b (format nil "~C[2J~C[H" #\Esc #\Esc))  ; clear + home
+  (backend-write b (format nil "~C[?25l" #\Esc))  ; hide cursor
   b)
 
 (defmethod shutdown-backend ((b simple-backend))
+  (backend-write b (format nil "~C[?25h" #\Esc))  ; show cursor
   (values))
 
 (defmethod suspend-backend ((b simple-backend))
+  (backend-write b (format nil "~C[?25h" #\Esc))
   (values))
 
 (defmethod resume-backend ((b simple-backend))
+  (backend-write b (format nil "~C[?25l" #\Esc))
   (values))
 
 (defmethod backend-size ((b simple-backend))
-  ;; Try ioctl, fall back to 80x24
-  (values 80 24))
+  (or (ignore-errors
+        (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
+                                      (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))))
+      (values 80 24)))
 
 (defmethod backend-write ((b simple-backend) string)
   (let ((stream (backend-output-stream b)))
@@ -31,16 +47,29 @@
     (finish-output stream)
     (length string)))
 
+(defmethod capable-p ((b simple-backend) feature)
+  (declare (ignore feature))
+  nil)
+
+(defun %cursor-move (x y)
+  (format nil "~C[~d;~dH" #\Esc (1+ y) (1+ x)))
+
+(defmethod cursor-hide ((b simple-backend))
+  (backend-write b (format nil "~C[?25l" #\Esc)))
+
+(defmethod cursor-show ((b simple-backend))
+  (backend-write b (format nil "~C[?25h" #\Esc)))
+
+(defmethod cursor-move ((b simple-backend) x y)
+  (backend-write b (%cursor-move x y)))
+
 (defmethod draw-text ((b simple-backend) x y string fg bg
                       &key bold italic underline reverse dim blink
                       &allow-other-keys)
- (declare (ignore x y fg bg bold italic underline reverse dim blink))
- (backend-write b string))
+  (declare (ignore fg bg bold italic underline reverse dim blink))
+  (backend-write b (concatenate 'string (%cursor-move x y) string)))
 
 (defun %simple-border-char (pos)
-  "Return ASCII border character at POS.
-POS is :top-left, :top-right, :bottom-left, :bottom-right,
-:horizontal, or :vertical."
   (case pos
     ((:top-left :top-right :bottom-left :bottom-right) #\+)
     (:horizontal #\-)
@@ -55,10 +84,8 @@ POS is :top-left, :top-right, :bottom-left, :bottom-right,
         (tr (%simple-border-char :top-right))
         (bl (%simple-border-char :bottom-left))
         (br (%simple-border-char :bottom-right)))
-    ;; Position cursor with newlines and spaces (no escape sequences)
-    (dotimes (row y) (backend-write b (string #\Newline)))
-    ;; Top edge with optional title
-    (backend-write b (make-string x :initial-element #\space))
+    ;; Top edge
+    (backend-write b (%cursor-move x y))
     (backend-write b (string tl))
     (if (and title (plusp (length title)))
         (let* ((align (or title-align :left))
@@ -83,23 +110,23 @@ POS is :top-left, :top-right, :bottom-left, :bottom-right,
     (backend-write b (string tr))
     ;; Sides
     (loop for i from 1 below (1- height)
-          do (backend-write b (string #\Newline))
-             (backend-write b (make-string x :initial-element #\space))
+          do (backend-write b (%cursor-move x (+ y i)))
              (backend-write b (string v))
              (backend-write b (make-string (- width 2) :initial-element #\space))
              (backend-write b (string v)))
     ;; Bottom edge
-    (backend-write b (string #\Newline))
-    (backend-write b (make-string x :initial-element #\space))
+    (backend-write b (%cursor-move x (+ y height -1)))
     (backend-write b (string bl))
     (backend-write b (make-string (- width 2) :initial-element h))
     (backend-write b (string br))))
 
 (defmethod draw-rect ((b simple-backend) x y width height
                       &key bg)
-  (declare (ignore x y width height bg))
-  ;; On simple backend, background fill is a no-op
-  (values))
+  (declare (ignore bg))
+  (let ((line (make-string width :initial-element #\space)))
+    (loop for row from 0 below height
+          do (backend-write b (%cursor-move x (+ y row)))
+             (backend-write b line))))
 
 (defmethod draw-link ((b simple-backend) x y string url
                       &key fg bg)
@@ -109,7 +136,4 @@ POS is :top-left, :top-right, :bottom-left, :bottom-right,
 (defmethod draw-ellipsis ((b simple-backend) x y width
                           &key fg bg)
   (declare (ignore width fg bg))
-  ;; Position using newlines+spaces (simple-backend pattern)
-  (dotimes (row y) (backend-write b (string #\Newline)))
-  (backend-write b (make-string x :initial-element #\Space))
-  (backend-write b "..."))
+  (draw-text b x y "..." nil nil))