Add focus event support gated by DEC mode 1004

Focus in/out events are now sent to the terminal when the application
has enabled focus reporting via DECSET 1004. The Zig module checks
the terminal mode before encoding, so focus events are silently
ignored for shells that haven't requested them. Emacs focus-in-hook
and focus-out-hook are connected in ghostel-mode and cleaned up
in the process sentinel.

Author: dakra

ghostel.el

@@ -35,6 +35,7 @@
 (declare-function ghostel--scroll "ghostel-module")
 (declare-function ghostel--encode-key "ghostel-module")
 (declare-function ghostel--mouse-event "ghostel-module")
+(declare-function ghostel--focus-event "ghostel-module")
 
 ;;; Customization
 
@@ -523,6 +524,26 @@ DIR may be a file:// URL or a plain path."
       (when (and path (file-directory-p path))
         (setq default-directory (file-name-as-directory path))))))
 
+;;; Focus events
+
+(defun ghostel--focus-in ()
+  "Notify the terminal that Emacs gained focus.
+Only sends the event if the terminal has enabled focus reporting (mode 1004)."
+  (when (and (eq major-mode 'ghostel-mode)
+             ghostel--term
+             ghostel--process
+             (process-live-p ghostel--process))
+    (ghostel--focus-event ghostel--term t)))
+
+(defun ghostel--focus-out ()
+  "Notify the terminal that Emacs lost focus.
+Only sends the event if the terminal has enabled focus reporting (mode 1004)."
+  (when (and (eq major-mode 'ghostel-mode)
+             ghostel--term
+             ghostel--process
+             (process-live-p ghostel--process))
+    (ghostel--focus-event ghostel--term nil)))
+
 ;;; Process management
 
 (defun ghostel--filter (process output)
@@ -545,6 +566,8 @@ PROCESS is the shell process."
       (when ghostel--redraw-timer
         (cancel-timer ghostel--redraw-timer)
         (setq ghostel--redraw-timer nil))
+      (remove-hook 'focus-in-hook #'ghostel--focus-in)
+      (remove-hook 'focus-out-hook #'ghostel--focus-out)
       (let ((inhibit-read-only t))
         (goto-char (point-max))
         (insert "\n[Process exited]\n")))))
@@ -636,7 +659,8 @@ PROCESS is the shell process, WINDOWS is the list of windows."
   (setq-local scroll-conservatively 101)
   (setq-local window-adjust-process-window-size-function
               #'ghostel--window-adjust-process-window-size)
-  )
+  (add-hook 'focus-in-hook #'ghostel--focus-in)
+  (add-hook 'focus-out-hook #'ghostel--focus-out))
 
 ;;; Entry point
 

src/module.zig

@@ -242,9 +242,17 @@ fn fnMouseEvent(raw_env: ?*c.emacs_env, _: isize, args: [*c]c.emacs_value, _: ?*
 
 /// (ghostel--focus-event TERM GAINED)
 /// Encode a focus gained/lost event and send to the PTY.
+/// Only sends if the terminal has enabled focus reporting (DEC mode 1004).
 fn fnFocusEvent(raw_env: ?*c.emacs_env, _: isize, args: [*c]c.emacs_value, _: ?*anyopaque) callconv(.c) c.emacs_value {
     const env = emacs.Env.init(raw_env.?);
-    _ = env.getUserPtr(Terminal, args[0]) orelse return env.nil();
+    const term = env.getUserPtr(Terminal, args[0]) orelse return env.nil();
+
+    // Only send focus events if the terminal has enabled mode 1004
+    // Construct mode value manually: DEC private mode 1004 = value & 0x7FFF, ansi=false (bit 15=0)
+    const focus_mode: gt.c.GhosttyMode = 1004;
+    if (!term.isModeEnabled(focus_mode)) {
+        return env.nil();
+    }
 
     const gained = env.isNotNil(args[1]);
     const event: gt.c.GhosttyFocusEvent = if (gained) gt.c.GHOSTTY_FOCUS_GAINED else gt.c.GHOSTTY_FOCUS_LOST;
@@ -255,6 +263,10 @@ fn fnFocusEvent(raw_env: ?*c.emacs_env, _: isize, args: [*c]c.emacs_value, _: ?*
         return env.nil();
     }
 
+    // Stash env for the flush callback
+    term.env = env;
+    defer term.env = null;
+
     _ = env.call1(env.intern("ghostel--flush-output"), env.makeString(buf[0..written]));
     return env.t();
 }

src/terminal.zig

@@ -194,6 +194,15 @@ pub fn getPwd(self: *Self) ?[]const u8 {
     return pwd.ptr[0..pwd.len];
 }
 
+/// Check if a terminal mode is enabled.
+pub fn isModeEnabled(self: *Self, mode: gt.c.GhosttyMode) bool {
+    var enabled: bool = false;
+    if (gt.c.ghostty_terminal_mode_get(self.terminal, mode, &enabled) != gt.SUCCESS) {
+        return false;
+    }
+    return enabled;
+}
+
 /// Emacs finalizer — called when the user-ptr is garbage collected.
 pub fn emacsFinalize(ptr: ?*anyopaque) callconv(.c) void {
     if (ptr) |p| {

test/ghostel-test.el

@@ -360,6 +360,34 @@
       (ghostel--update-directory "file:///usr")
       (ghostel-test--assert-equal "dedup" old ghostel--last-directory))))
 
+;; -----------------------------------------------------------------------
+;; Test: focus events gated by mode 1004
+;; -----------------------------------------------------------------------
+
+(defun ghostel-test-focus-events ()
+  "Test that focus events are only sent when mode 1004 is enabled."
+  (message "--- focus events ---")
+  (let ((term (ghostel--new 25 80 1000))
+        (ghostel--flush-output-data nil))
+    ;; Without mode 1004 enabled, focus-event should return nil (not sent)
+    (ghostel-test--assert-equal "focus ignored without mode 1004"
+                                nil
+                                (ghostel--focus-event term t))
+    ;; Enable mode 1004 via DECSET
+    (ghostel--write-input term "\e[?1004h")
+    ;; Now focus-event should return t (sent)
+    (ghostel-test--assert-equal "focus sent with mode 1004"
+                                t
+                                (ghostel--focus-event term t))
+    (ghostel-test--assert-equal "focus-out sent with mode 1004"
+                                t
+                                (ghostel--focus-event term nil))
+    ;; Disable mode 1004 via DECRST
+    (ghostel--write-input term "\e[?1004l")
+    (ghostel-test--assert-equal "focus ignored after mode 1004 reset"
+                                nil
+                                (ghostel--focus-event term t))))
+
 ;; -----------------------------------------------------------------------
 ;; Test: incremental (partial) redraw
 ;; -----------------------------------------------------------------------
@@ -426,6 +454,7 @@
   (ghostel-test-title)
   (ghostel-test-crlf)
   (ghostel-test-incremental-redraw)
+  (ghostel-test-focus-events)
 
   ;; Integration test (spawns a real shell)
   (ghostel-test-shell-integration)