Suppress spurious SIGWINCH on minibuffer-induced window shrink

When the minibuffer opens (M-x, vertico, consult, etc.), Emacs shrinks
the window displaying the terminal, triggering
window-configuration-change-hook → set-process-window-size and thus
SIGWINCH to the shell.  Closing the minibuffer sends a second one.
Fish repaints its whole prompt on SIGWINCH; complex TUIs redraw the
full screen.  Both are jarring no-ops from the user's perspective.

Solution: treat minibuffer-induced height shrinks as crops, matching
how a normal buffer behaves when the minibuffer steals space — the
bottom rows are simply hidden, no signal is sent.  When the minibuffer
closes and the window grows back, the size matches the committed PTY
size, so no signal is sent either.

Refinements to keep the cropping correct:

- Only crop while the terminal is on the *primary* screen.  Apps on
  the alternate screen buffer (vim, htop, less, Claude Code) own the
  full viewport and need SIGWINCH to re-layout for the smaller window.
  New Zig binding `ghostel--alt-screen-p' checks DEC modes
  1049/1047/47 in one native call.

- If the user switches focus into the ghostel window while the
  minibuffer is still open, commit the current (smaller) size so the
  shell/app knows its real viewport — they are now actively using it.
  Handled by `ghostel--commit-cropped-size' hooked into
  window-selection-change-functions.

- Track `ghostel--term-cols' alongside `ghostel--term-rows' so no-op
  resizes (window merely moves) are skipped.

Module version bumped to 0.17.0 for the new export.

Author: emil-e

build.zig.zon

@@ -1,6 +1,6 @@
 .{
     .name = .ghostel,
-    .version = "0.16.1",
+    .version = "0.16.2",
     .paths = .{""},
     .fingerprint = 0x5a44bdd1198a0f4b,
     .dependencies = .{

evil-ghostel.el

@@ -4,7 +4,7 @@
 
 ;; Author: Daniel Kraus <daniel@kraus.my>
 ;; URL: https://github.com/dakra/ghostel
-;; Version: 0.16.1
+;; Version: 0.16.2
 ;; Package-Requires: ((emacs "28.1") (evil "1.0") (ghostel "0.8.0"))
 ;; SPDX-License-Identifier: GPL-3.0-or-later
 

ghostel.el

@@ -4,7 +4,7 @@
 
 ;; Author: Daniel Kraus <daniel@kraus.my>
 ;; URL: https://github.com/dakra/ghostel
-;; Version: 0.16.1
+;; Version: 0.16.2
 ;; Keywords: terminals
 ;; Package-Requires: ((emacs "28.1"))
 ;; SPDX-License-Identifier: GPL-3.0-or-later
@@ -524,7 +524,7 @@ before sending the input."
 Customize this when downloading pre-built modules from a fork or mirror."
   :type 'string)
 
-(defconst ghostel--minimum-module-version "0.16.1"
+(defconst ghostel--minimum-module-version "0.16.2"
   "Minimum native module version required by this Elisp version.
 Bump this only when the Elisp code requires a newer native module
 \(e.g. new Zig-exported function or changed calling convention).")
@@ -537,6 +537,7 @@ Bump this only when the Elisp code requires a newer native module
 (declare-function ghostel--encode-key "ghostel-module")
 (declare-function ghostel--focus-event "ghostel-module")
 (declare-function ghostel--mode-enabled "ghostel-module")
+(declare-function ghostel--alt-screen-p "ghostel-module")
 (declare-function ghostel--copy-all-text "ghostel-module")
 (declare-function ghostel--module-version "ghostel-module")
 (declare-function ghostel--mouse-event "ghostel-module")
@@ -795,6 +796,10 @@ entry points so tests run without the module present."
   "Row count of the native terminal, for viewport/scrollback arithmetic.
 Updated whenever the terminal is created or resized.")
 
+(defvar-local ghostel--term-cols nil
+  "Column count of the native terminal.
+Updated whenever the terminal is created or resized.")
+
 (defvar-local ghostel--copy-mode-active nil
   "Non-nil when copy mode is active.")
 
@@ -3159,24 +3164,81 @@ PROCESS is the shell process, WINDOWS is the list of windows."
     (when (and size (buffer-live-p buffer))
       (with-current-buffer buffer
         (when ghostel--term
-          (ghostel--set-size ghostel--term (max 1 height) (max 1 width))
-          (setq ghostel--term-rows height)
-          (setq ghostel--force-next-redraw t)
-          ;; Redraw synchronously so the buffer is updated before
-          ;; Emacs displays the stale content at the new window size.
-          (when ghostel--redraw-timer
-            (cancel-timer ghostel--redraw-timer)
-            (setq ghostel--redraw-timer nil))
-          ;; `ghostel--redraw-resize-active' lets `ghostel--window-anchored-p'
-          ;; treat Emacs-induced `window-start' drift (from `keep-point-visible'
-          ;; when a minibuffer-triggered resize shrinks the body) as drift,
-          ;; not as a user scroll.
-          (let ((ghostel--redraw-resize-active t))
-            (ghostel--delayed-redraw buffer)))))
+          (cond
+           ;; No change — skip entirely.
+           ((and (eql height ghostel--term-rows)
+                 (eql width ghostel--term-cols))
+            (setq size nil))
+           ;; Crop: minibuffer is active, only height shrank, width unchanged, and the
+           ;; terminal is on the primary screen.  Defer the resize so no SIGWINCH is sent
+           ;; — the Emacs window naturally hides the bottom rows, just like a normal
+           ;; buffer.  Alt-screen apps (vim, htop) own the full viewport and must be told
+           ;; the real size to re-layout, so they take the normal-resize path.  If the
+           ;; user switches focus into the ghostel window while the minibuffer is still
+           ;; open, `ghostel--commit-cropped-size' commits the smaller size then.
+           ((and (> (minibuffer-depth) 0)
+                 (eql width ghostel--term-cols)
+                 (< height ghostel--term-rows)
+                 (not (ghostel--alt-screen-p ghostel--term)))
+            (setq size nil))
+           ;; Real resize — update the terminal model and redraw.
+           (t
+            (ghostel--set-size ghostel--term (max 1 height) (max 1 width))
+            (setq ghostel--term-rows height)
+            (setq ghostel--term-cols width)
+            (setq ghostel--force-next-redraw t)
+            ;; Redraw synchronously so the buffer is updated before
+            ;; Emacs displays the stale content at the new window size.
+            (when ghostel--redraw-timer
+              (cancel-timer ghostel--redraw-timer)
+              (setq ghostel--redraw-timer nil))
+            ;; `ghostel--redraw-resize-active' lets `ghostel--window-anchored-p'
+            ;; treat Emacs-induced `window-start' drift (from `keep-point-visible'
+            ;; when a minibuffer-triggered resize shrinks the body) as drift,
+            ;; not as a user scroll.
+            (let ((ghostel--redraw-resize-active t))
+              (ghostel--delayed-redraw buffer)))))))
     ;; Return size — Emacs calls set-process-window-size (SIGWINCH)
-    ;; after this function returns, matching eat/vterm timing.
+    ;; after this function returns.  nil suppresses the call.
     size))
 
+(defun ghostel--commit-cropped-size (window)
+  "Commit WINDOW's size if the user focused into a cropped ghostel window.
+When the minibuffer opens, `ghostel--window-adjust-process-window-size'
+skips the resize so the PTY keeps its original row count and the bottom
+rows are just hidden.  But if the user switches focus into the ghostel
+window while the minibuffer is still up, they are now actively using
+the smaller viewport — commit the size so the shell/app knows its real
+dimensions.
+
+Intended for buffer-local `window-selection-change-functions'.  When
+registered buffer-locally, Emacs calls this with WINDOW and makes its
+buffer current; we only commit when WINDOW has become the selected
+window (not when it has just been deselected)."
+  (when (and (> (minibuffer-depth) 0)
+             (window-live-p window)
+             (eq window (frame-selected-window (window-frame window)))
+             ghostel--term
+             ghostel--process
+             (process-live-p ghostel--process))
+    (let ((height (window-body-height window))
+          (width (window-max-chars-per-line window))
+          (buf (current-buffer)))
+      (unless (and (eql height ghostel--term-rows)
+                   (eql width ghostel--term-cols))
+        (ghostel--set-size ghostel--term
+                           (max 1 height) (max 1 width))
+        (setq ghostel--term-rows height
+              ghostel--term-cols width
+              ghostel--force-next-redraw t)
+        (set-process-window-size ghostel--process
+                                 (max 1 height) (max 1 width))
+        (when ghostel--redraw-timer
+          (cancel-timer ghostel--redraw-timer)
+          (setq ghostel--redraw-timer nil))
+        (let ((ghostel--redraw-resize-active t))
+          (ghostel--delayed-redraw buf))))))
+
 
 
 ;;; Major mode
@@ -3203,6 +3265,10 @@ PROCESS is the shell process, WINDOWS is the list of windows."
   (add-function :after after-focus-change-function #'ghostel--focus-change)
   (add-hook 'window-selection-change-functions #'ghostel--focus-change)
   (add-hook 'window-buffer-change-functions #'ghostel--focus-change)
+  ;; Buffer-local so it only fires for windows showing this buffer, and
+  ;; receives WINDOW directly (rather than FRAME as the default binding).
+  (add-hook 'window-selection-change-functions
+            #'ghostel--commit-cropped-size nil t)
   (ghostel--suppress-interfering-modes)
   (setq ghostel--scroll-intercept-active t)
   ;; Let C-g reach the keymap instead of triggering keyboard-quit.
@@ -3245,6 +3311,7 @@ displayed, so a mismatch at creation time self-corrects."
         (setq ghostel--term
               (ghostel--new height width ghostel-max-scrollback))
         (setq ghostel--term-rows height)
+        (setq ghostel--term-cols width)
         (ghostel--apply-palette ghostel--term))
       (ghostel--start-process))))
 
@@ -3297,6 +3364,7 @@ Signals `user-error' if BUFFER already has a live ghostel process."
         (setq ghostel--term
               (ghostel--new height width ghostel-max-scrollback))
         (setq ghostel--term-rows height)
+        (setq ghostel--term-cols width)
         (ghostel--apply-palette ghostel--term)
         (ghostel--spawn-pty program args height width
                             "erase '^?' iutf8 -ixon echo" nil remote-p)))))

src/module.zig

@@ -13,7 +13,7 @@ const input = @import("input.zig");
 const c = emacs.c;
 
 /// Module version — keep in sync with ghostel.el and build.zig.zon.
-const version = "0.16.1";
+const version = "0.16.2";
 
 // ---------------------------------------------------------------------------
 // Module entry point
@@ -42,6 +42,7 @@ export fn emacs_module_init(runtime: *c.struct_emacs_runtime) callconv(.c) c_int
     env.bindFunction("ghostel--set-palette", 2, 2, &fnSetPalette, "Set the ANSI color palette.\n\n(ghostel--set-palette TERM COLORS-STRING)");
     env.bindFunction("ghostel--set-default-colors", 3, 3, &fnSetDefaultColors, "Set default foreground and background colors.\n\n(ghostel--set-default-colors TERM FG-HEX BG-HEX)");
     env.bindFunction("ghostel--mode-enabled", 2, 2, &fnModeEnabled, "Return t if terminal DEC private MODE is enabled.\n\n(ghostel--mode-enabled TERM MODE)");
+    env.bindFunction("ghostel--alt-screen-p", 1, 1, &fnAltScreen, "Return t if terminal is on the alternate screen buffer.\n\n(ghostel--alt-screen-p TERM)");
     env.bindFunction("ghostel--cursor-position", 1, 1, &fnCursorPosition, "Return terminal cursor position as (COL . ROW), 0-indexed.\n\n(ghostel--cursor-position TERM)");
     env.bindFunction("ghostel--cursor-pending-wrap-p", 1, 1, &fnCursorPendingWrap, "Return t if the cursor is in pending-wrap state.\n\n(ghostel--cursor-pending-wrap-p TERM)");
     env.bindFunction("ghostel--debug-state", 1, 1, &fnDebugState, "Return debug info about terminal/render state.\n\n(ghostel--debug-state TERM)");
@@ -767,6 +768,14 @@ fn fnModeEnabled(raw_env: ?*c.emacs_env, _: isize, args: [*c]c.emacs_value, _: ?
     return if (term.isModeEnabled(mode)) env.t() else env.nil();
 }
 
+/// (ghostel--alt-screen-p TERM)
+/// Return t if the terminal is on the alternate screen buffer.
+fn fnAltScreen(raw_env: ?*c.emacs_env, _: isize, args: [*c]c.emacs_value, _: ?*anyopaque) callconv(.c) c.emacs_value {
+    const env = emacs.Env.init(raw_env.?);
+    const term = env.getUserPtr(Terminal, args[0]) orelse return env.nil();
+    return if (term.isAltScreen()) env.t() else env.nil();
+}
+
 /// (ghostel--set-palette TERM COLORS-STRING)
 /// Set the 16 ANSI colors from a concatenated hex string like "#000000#aa0000...".
 /// The remaining 240 palette entries are taken from the terminal's current palette.

src/terminal.zig

@@ -278,6 +278,15 @@ pub fn isModeEnabled(self: *Self, mode: gt.c.GhosttyMode) bool {
     return enabled;
 }
 
+/// Returns true if the terminal is on the alternate screen buffer
+/// (DEC private modes 1049, 1047, or legacy 47 set).  Used to decide
+/// whether full-screen apps (vim, htop, less) own the viewport.
+pub fn isAltScreen(self: *Self) bool {
+    return self.isModeEnabled(@as(gt.c.GhosttyMode, 1049)) or
+        self.isModeEnabled(@as(gt.c.GhosttyMode, 1047)) or
+        self.isModeEnabled(@as(gt.c.GhosttyMode, 47));
+}
+
 /// Get the total number of rows (scrollback + active screen).
 pub fn getTotalRows(self: *Self) usize {
     var total: usize = 0;