patches: fix O(position) performance via UAZoomEnabled caching

Root cause (per Opus analysis): UAZoomEnabled() is a synchronous
Mach IPC roundtrip to macOS Accessibility server, called 3x per
redisplay cycle. At 60fps = 180 IPC roundtrips/second blocking the
main thread. Combined with Emacs's inherent O(position) redisplay
cost, this compounded into progressive choppy behavior.

Fix 1: ns_zoom_enabled_p() caches UAZoomEnabled() for 1 second.
Fix 2: ns_zoom_track_completion() rate-limited to 2 Hz.

Also includes BUF_CHARS_MODIFF fix (patch 0009) for VoiceOver cache.

patches/0000-ns-integrate-with-macOS-Zoom-for-cursor-tracking.patch

@@ -1,7 +1,7 @@
-From b38d702cb19f2b7c36d88d7e397323ea1aca1c9b Mon Sep 17 00:00:00 2001
+From 8cecc655267f3adc31230a76d0d470159adc9d87 Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 22:39:35 +0100
-Subject: [PATCH 01/10] ns: integrate with macOS Zoom for cursor tracking
+Subject: [PATCH 01/11] ns: integrate with macOS Zoom for cursor tracking
 
 Inform macOS Zoom of the text cursor position so the zoomed viewport
 follows keyboard focus in Emacs.

patches/0001-ns-add-accessibility-base-classes-and-text-extractio.patch

@@ -1,7 +1,7 @@
-From e6800d12d350def06dd6475fcb807ceaf7f82e02 Mon Sep 17 00:00:00 2001
+From a750bf8ae17dd0dd6c14a23376d012c61367227f Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 02/10] ns: add accessibility base classes and text extraction
+Subject: [PATCH 02/11] ns: add accessibility base classes and text extraction
 
 Add the foundation for macOS VoiceOver accessibility in the NS
 (Cocoa) port.  No existing code paths are modified.

patches/0002-ns-implement-buffer-accessibility-element-core-proto.patch

@@ -1,7 +1,7 @@
-From d3dd16835ff6b7456f987893ef610e3847a92fde Mon Sep 17 00:00:00 2001
+From cd8512d541e63f044086d1dfd2fe44069d4c09ca Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 03/10] ns: implement buffer accessibility element (core
+Subject: [PATCH 03/11] ns: implement buffer accessibility element (core
  protocol)
 
 Implement the NSAccessibility text protocol for Emacs buffer windows.

patches/0003-ns-add-buffer-notification-dispatch-and-mode-line-el.patch

@@ -1,7 +1,7 @@
-From 601df3982e20e60f041fa2658aa7ef1efb69939b Mon Sep 17 00:00:00 2001
+From 2cb651607c84eb100729db5d4c113d7fcf4e1048 Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 04/10] ns: add buffer notification dispatch and mode-line
+Subject: [PATCH 04/11] ns: add buffer notification dispatch and mode-line
  element
 
 Add VoiceOver notification methods and mode-line readout.

patches/0004-ns-add-interactive-span-elements-for-Tab-navigation.patch

@@ -1,7 +1,7 @@
-From 8c67a2b5a89ac302cbac91790fdfb6827b74285a Mon Sep 17 00:00:00 2001
+From e04d6ef8808c1e00b37fca85e6ac0a7f6104bdb7 Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 05/10] ns: add interactive span elements for Tab navigation
+Subject: [PATCH 05/11] ns: add interactive span elements for Tab navigation
 
 * src/nsterm.m (ns_ax_scan_interactive_spans): New function.
 (EmacsAccessibilityInteractiveSpan): Implement AXButton/AXLink

patches/0005-ns-integrate-accessibility-with-EmacsView-and-redisp.patch

@@ -1,7 +1,7 @@
-From 3237374282389cd61bcd99beed187ec75d1b06fc Mon Sep 17 00:00:00 2001
+From 88bcf29875755897a3d3d4cef04e2c0044ac8b9d Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 06/10] ns: integrate accessibility with EmacsView and
+Subject: [PATCH 06/11] ns: integrate accessibility with EmacsView and
  redisplay
 
 Wire the accessibility infrastructure into EmacsView and the

patches/0006-doc-add-VoiceOver-accessibility-section-to-macOS-app.patch

@@ -1,7 +1,7 @@
-From e2b76f1850489e8188236bed10e4d7f28e5cde2b Mon Sep 17 00:00:00 2001
+From 8b7858f8e43e6bd7abb58ca2da0883341b9c446a Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 07/10] doc: add VoiceOver accessibility section to macOS
+Subject: [PATCH 07/11] doc: add VoiceOver accessibility section to macOS
  appendix
 
 * doc/emacs/macos.texi (VoiceOver Accessibility): New node.  Document

patches/0007-ns-announce-overlay-completion-candidates-for-VoiceO.patch

@@ -1,7 +1,7 @@
-From 3e868d0234c858fa20588e664354685ef8b08576 Mon Sep 17 00:00:00 2001
+From 314e2a5f406a8eb0e6909be6e07fe7e8ddd1c440 Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 14:46:25 +0100
-Subject: [PATCH 08/10] ns: announce overlay completion candidates for
+Subject: [PATCH 08/11] ns: announce overlay completion candidates for
  VoiceOver
 
 Completion frameworks such as Vertico, Ivy, and Icomplete render

patches/0008-ns-announce-child-frame-completion-candidates-for-Vo.patch

@@ -1,7 +1,7 @@
-From 5aba3491f8f5268f2e6093003b79fe69e7932a4b Mon Sep 17 00:00:00 2001
+From a75ee6aff3734bd053865b3df734b75642f7305e Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 16:01:29 +0100
-Subject: [PATCH 09/10] ns: announce child frame completion candidates for
+Subject: [PATCH 09/11] ns: announce child frame completion candidates for
  VoiceOver
 
 Completion frameworks such as Corfu, Company-box, and similar

patches/0009-perf-use-BUF_CHARS_MODIFF-for-AX-text-cache-validity.patch

@@ -1,7 +1,7 @@
-From 4b739781a019fd1ad5b6ac1c9c12dc62e2c82ec3 Mon Sep 17 00:00:00 2001
+From 1d67b993dc9072f36a7742fc3d284b7bd935a84d Mon Sep 17 00:00:00 2001
 From: Daneel <daneel@sukany.cz>
 Date: Sun, 1 Mar 2026 04:56:16 +0100
-Subject: [PATCH 10/10] perf: use BUF_CHARS_MODIFF for AX text cache validity
+Subject: [PATCH 10/11] perf: use BUF_CHARS_MODIFF for AX text cache validity
  in ensureTextCache
 
 The cache validity check in -[EmacsAccessibilityBuffer ensureTextCache]

patches/0010-perf-cache-UAZoomEnabled-and-rate-limit-completion-t.patch

@@ -0,0 +1,117 @@
+From 9e2b56b7aec560540ef9f49c9444c2c0fc903090 Mon Sep 17 00:00:00 2001
+From: Daneel <daneel@sukany.cz>
+Date: Sun, 1 Mar 2026 05:23:37 +0100
+Subject: [PATCH 11/11] perf: cache UAZoomEnabled() and rate-limit completion
+ tracking
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+UAZoomEnabled() performs a synchronous Mach IPC roundtrip to the macOS
+Accessibility server (~50-200 µs per call).  With three call sites in
+the redisplay hot path (ns_draw_window_cursor, ns_update_end fallback,
+ns_zoom_track_completion) this adds up to 150-600 µs of IPC overhead
+per redisplay cycle.  At 60 fps, that is 9-36 ms/s of pure IPC cost.
+The overhead blocks the main thread, extending the inter-frame interval
+and making cursor movement feel choppy, especially at the end of large
+files where Emacs's own redisplay work is already at its maximum.
+
+* src/nsterm.m (ns_zoom_cached_enabled, ns_zoom_cache_time): New
+static variables.
+(ns_zoom_enabled_p): New inline wrapper around UAZoomEnabled().
+Caches the result for 1 second using CFAbsoluteTimeGetCurrent(), a
+near-free VDSO call.  Zoom state changes only on explicit user action
+in System Settings, so a 1-second TTL is indistinguishable from
+querying on every frame.  Replaces all three UAZoomEnabled() call
+sites.
+(ns_zoom_track_completion): Add 500 ms rate limit.  Completion
+candidate detection requires FOR_EACH_FRAME iteration and
+Fget_char_property calls.  Completion state changes at human
+interaction speed (well below 2 Hz), so 500 ms polling is
+imperceptible while eliminating per-redisplay Lisp overhead.
+---
+ src/nsterm.m | 43 ++++++++++++++++++++++++++++++++++++++++---
+ 1 file changed, 40 insertions(+), 3 deletions(-)
+
+diff --git a/src/nsterm.m b/src/nsterm.m
+index e3f9466..590287a 100644
+--- a/src/nsterm.m
++++ b/src/nsterm.m
+@@ -1092,6 +1092,31 @@ static NSRect constrain_frame_rect(NSRect frameRect, bool isFullscreen)
+    ivy-current-match, corfu-current that mark the selected candidate.  */
+ static bool ns_ax_face_is_selected (Lisp_Object face);
+ 
++/* Cached wrapper around UAZoomEnabled().
++   UAZoomEnabled() performs a synchronous Mach IPC roundtrip to the
++   macOS Accessibility server (~50-200 µs per call).  With three call
++   sites in the redisplay hot path the overhead accumulates to
++   150-600 µs per frame.  Zoom state only changes on explicit user
++   action in System Settings, so a 1-second TTL is both safe and
++   indistinguishable from querying on every frame.
++
++   Uses CFAbsoluteTimeGetCurrent() (a VDSO read on modern macOS, ~5 ns)
++   to avoid a second IPC roundtrip for time.  */
++static BOOL  ns_zoom_cached_enabled;
++static CFAbsoluteTime ns_zoom_cache_time;
++
++static BOOL
++ns_zoom_enabled_p (void)
++{
++  CFAbsoluteTime now = CFAbsoluteTimeGetCurrent ();
++  if (now - ns_zoom_cache_time > 1.0)
++    {
++      ns_zoom_cached_enabled = UAZoomEnabled ();
++      ns_zoom_cache_time = now;
++    }
++  return ns_zoom_cached_enabled;
++}
++
+ /* Scan overlay before-string / after-string properties in the
+    selected window for a completion candidate with a "selected"
+    face.  Return the 0-based visual line index of the selected
+@@ -1215,11 +1240,23 @@ If a completion candidate is selected (overlay or child frame),
+ static void
+ ns_zoom_track_completion (struct frame *f, EmacsView *view)
+ {
+-  if (!UAZoomEnabled ())
++  if (!ns_zoom_enabled_p ())
+     return;
+   if (!WINDOWP (f->selected_window))
+     return;
+ 
++  /* Rate-limit completion scan to 2 Hz.  Completion overlays and
++     child frames change at human interaction speed (<<10 Hz), so
++     checking every 500 ms is indistinguishable from every frame
++     while eliminating per-redisplay FOR_EACH_FRAME iteration.  */
++  {
++    static CFAbsoluteTime last_completion_track;
++    CFAbsoluteTime now = CFAbsoluteTimeGetCurrent ();
++    if (now - last_completion_track < 0.5)
++      return;
++    last_completion_track = now;
++  }
++
+   specpdl_ref count = SPECPDL_INDEX ();
+   record_unwind_current_buffer ();
+ 
+@@ -1323,7 +1360,7 @@ so the visual offset is (ov_line + 1) * line_h from
+      (zoomCursorUpdated is NO).  */
+ #if defined (MAC_OS_X_VERSION_MIN_REQUIRED) \
+     && MAC_OS_X_VERSION_MIN_REQUIRED >= 101000
+-  if (view && !view->zoomCursorUpdated && UAZoomEnabled ()
++  if (view && !view->zoomCursorUpdated && ns_zoom_enabled_p ()
+       && !NSIsEmptyRect (view->lastCursorRect))
+     {
+       NSRect r = view->lastCursorRect;
+@@ -3500,7 +3537,7 @@ EmacsView pixels (AppKit, flipped, top-left origin)
+ 
+ #if defined (MAC_OS_X_VERSION_MIN_REQUIRED) \
+     && MAC_OS_X_VERSION_MIN_REQUIRED >= 101000
+-	if (UAZoomEnabled ())
++	if (ns_zoom_enabled_p ())
+ 	  {
+ 	    NSRect windowRect = [view convertRect:r toView:nil];
+ 	    NSRect screenRect
+-- 
+2.43.0
+