Shrink terminal when tall glyphs push content off-screen

Emoji and other Unicode characters can fall back to taller fonts in
Emacs, expanding line height beyond what window-body-height assumes.
After enough such lines the bottom rows are pushed below the visible
window area.

After each redraw, check whether the last buffer position is still
visible.  When it is not, reduce the terminal by one row and
re-render so all content fits.  The adjustment is reset on window
resize so the terminal reclaims full height when possible.

Benchmarks show no regression (pos-visible-in-window-p is essentially
free for content that fits).

Author: dakra

ghostel.el

@@ -548,6 +548,9 @@ DIR is the module directory."
 (defvar-local ghostel--resize-timer nil
   "Timer for debounced SIGWINCH on alt screen.")
 
+(defvar-local ghostel--height-adjustment 0
+  "Rows subtracted from window-body-height to fit tall lines (emoji).")
+
 
 (defvar-local ghostel--last-directory nil
   "Last known working directory from OSC 7, used for dedup.")
@@ -1716,10 +1719,26 @@ frame after idle to improve interactive responsiveness."
             (ghostel--pin-window-start)))))))
 
 (defun ghostel--pin-window-start ()
-  "Pin the window so terminal row 1 stays at the top."
+  "Pin the window so terminal row 1 stays at the top.
+When tall glyphs (emoji) cause content to overflow the window,
+shrink the terminal by one row and re-render."
   (let ((win (get-buffer-window)))
     (when win
-      (set-window-start win (point-min)))))
+      (set-window-start win (point-min))
+      (when (and ghostel--term
+                 (> (point-max) (point-min))
+                 (not (pos-visible-in-window-p (1- (point-max)) win)))
+        ;; Content overflows — reduce terminal by one row.
+        (cl-incf ghostel--height-adjustment)
+        (let* ((height (- (window-body-height win)
+                          ghostel--height-adjustment))
+               (width (window-max-chars-per-line win)))
+          (when (> height 0)
+            (ghostel--set-size ghostel--term height width)
+            (when (and ghostel--process (process-live-p ghostel--process))
+              (set-process-window-size ghostel--process height width))
+            (ghostel--redraw ghostel--term ghostel-full-redraw)
+            (set-window-start win (point-min))))))))
 
 (defun ghostel-force-redraw ()
   "Force a full terminal redraw (for debugging)."
@@ -1738,6 +1757,7 @@ PROCESS is the shell process, WINDOWS is the list of windows."
   (let* ((window (car windows))
          (width (window-max-chars-per-line window))
          (height (window-body-height window)))
+    (setq ghostel--height-adjustment 0)
     (when ghostel--term
       (if (ghostel--mode-enabled ghostel--term 1049)
           ;; Alt screen: debounce the entire resize (terminal + SIGWINCH)