patches: fix O(buffer) cache invalidation caused by font-lock

BUF_CHARS_MODIFF fix — the core performance regression:
ensureTextCache checked BUF_MODIFF which font-lock bumps on every
redisplay. Each cursor movement in a large file triggered full buffer
rebuild. Now uses BUF_CHARS_MODIFF (changes only on char insert/delete).

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

@@ -1,7 +1,7 @@
-From 8ef9b7f50f9ebb1c23e8e8bf2b5158e073b35e37 Mon Sep 17 00:00:00 2001
+From b38d702cb19f2b7c36d88d7e397323ea1aca1c9b Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 22:39:35 +0100
-Subject: [PATCH 1/9] ns: integrate with macOS Zoom for cursor tracking
+Subject: [PATCH 01/10] 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 6e8cc407d6f407c2201a35438bab60b112a11c9e Mon Sep 17 00:00:00 2001
+From e6800d12d350def06dd6475fcb807ceaf7f82e02 Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 2/9] ns: add accessibility base classes and text extraction
+Subject: [PATCH 02/10] 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 aa788f7df93a3307f52cf10d16fe4af10eaae03d Mon Sep 17 00:00:00 2001
+From d3dd16835ff6b7456f987893ef610e3847a92fde Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 3/9] ns: implement buffer accessibility element (core
+Subject: [PATCH 03/10] 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 3da80e1c56c7270d458dfacd45e78e111359f526 Mon Sep 17 00:00:00 2001
+From 601df3982e20e60f041fa2658aa7ef1efb69939b Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 4/9] ns: add buffer notification dispatch and mode-line
+Subject: [PATCH 04/10] 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 9e13d137b009d4c2ecd2b6f55afa672637e8d62c Mon Sep 17 00:00:00 2001
+From 8c67a2b5a89ac302cbac91790fdfb6827b74285a Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 5/9] ns: add interactive span elements for Tab navigation
+Subject: [PATCH 05/10] 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 +1,8 @@
-From 8d882bfbad959b55915da0a43897acf2aca3b2ed Mon Sep 17 00:00:00 2001
+From 3237374282389cd61bcd99beed187ec75d1b06fc Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 6/9] ns: integrate accessibility with EmacsView and redisplay
+Subject: [PATCH 06/10] 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 6eddc6fb5933f561e7459198e403519d1c7eecd0 Mon Sep 17 00:00:00 2001
+From e2b76f1850489e8188236bed10e4d7f28e5cde2b Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
-Subject: [PATCH 7/9] doc: add VoiceOver accessibility section to macOS
+Subject: [PATCH 07/10] 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 +1,8 @@
-From 5cd1b5f46e670f031ce5fcca2d9312059d6efa87 Mon Sep 17 00:00:00 2001
+From 3e868d0234c858fa20588e664354685ef8b08576 Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 14:46:25 +0100
-Subject: [PATCH 8/9] ns: announce overlay completion candidates for VoiceOver
+Subject: [PATCH 08/10] ns: announce overlay completion candidates for
+ VoiceOver
 
 Completion frameworks such as Vertico, Ivy, and Icomplete render
 candidates via overlay before-string/after-string properties rather

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

@@ -1,7 +1,7 @@
-From 5db9f29f8a8fee97f01ae716f36f37c605dbd70d Mon Sep 17 00:00:00 2001
+From 5aba3491f8f5268f2e6093003b79fe69e7932a4b Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 16:01:29 +0100
-Subject: [PATCH 9/9] ns: announce child frame completion candidates for
+Subject: [PATCH 09/10] 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

@@ -0,0 +1,77 @@
+From 4b739781a019fd1ad5b6ac1c9c12dc62e2c82ec3 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
+ in ensureTextCache
+
+The cache validity check in -[EmacsAccessibilityBuffer ensureTextCache]
+used BUF_MODIFF, which is bumped by every text-property change ---
+including face applications by font-lock on each redisplay cycle.
+Since the AX text value contains only characters (no face or property
+data), property-only changes do not affect it.  Rebuilding the full
+buffer text on each font-lock pass is O(buffer-size) per redisplay,
+causing progressive slowdown proportional to how far the cursor is
+from the beginning of the file.
+
+Switch to BUF_CHARS_MODIFF, which is bumped only when characters are
+actually inserted or deleted.  This matches the semantic of 'did the
+text change' and is the approach used by WebKit and NSTextView.
+
+BUF_OVERLAY_MODIFF is intentionally not tracked here (unchanged):
+overlay content is handled by separate announcements in
+postAccessibilityNotificationsForFrame, and including it in this
+check would prevent those announcements from firing.
+---
+ src/nsterm.m | 27 ++++++++++++++++++---------
+ 1 file changed, 18 insertions(+), 9 deletions(-)
+
+diff --git a/src/nsterm.m b/src/nsterm.m
+index 12c451b..e3f9466 100644
+--- a/src/nsterm.m
++++ b/src/nsterm.m
+@@ -8148,16 +8148,25 @@ - (void)ensureTextCache
+   if (!b)
+     return;
+ 
+-  ptrdiff_t modiff = BUF_MODIFF (b);
+-  ptrdiff_t pt = BUF_PT (b);
+-  NSUInteger textLen = cachedText ? [cachedText length] : 0;
+-  /* Cache validity: track BUF_MODIFF and buffer narrowing.
++  /* Use BUF_CHARS_MODIFF, not BUF_MODIFF, for cache validity.
++     BUF_MODIFF is bumped by every text-property change, including
++     font-lock face applications on every redisplay.  AX text contains
++     only characters, not face data, so property-only changes do not
++     affect the cached value.  Rebuilding the full buffer text on
++     each font-lock pass is O(buffer-size) per redisplay --- this
++     causes progressive slowdown when scrolling through large files.
++     BUF_CHARS_MODIFF is bumped only on actual character insertions
++     and deletions, matching the semantic of "did the text change".
++     This is the pattern used by WebKit and NSTextView.
+      Do NOT track BUF_OVERLAY_MODIFF here --- overlay text is not
+      included in the cached AX text (it is handled separately via
+-     explicit announcements).  Including overlay_modiff would
+-     silently update cachedOverlayModiff and prevent the
+-     notification dispatch from detecting overlay changes.  */
+-  if (cachedText && cachedTextModiff == modiff
++     explicit announcements in postAccessibilityNotificationsForFrame).
++     Including overlay_modiff would silently update cachedOverlayModiff
++     and prevent the notification dispatch from detecting changes.  */
++  ptrdiff_t chars_modiff = BUF_CHARS_MODIFF (b);
++  ptrdiff_t pt = BUF_PT (b);
++  NSUInteger textLen = cachedText ? [cachedText length] : 0;
++  if (cachedText && cachedTextModiff == chars_modiff
+       && cachedTextStart == BUF_BEGV (b)
+       && pt >= cachedTextStart
+       && (textLen == 0
+@@ -8173,7 +8182,7 @@ included in the cached AX text (it is handled separately via
+     {
+       [cachedText release];
+       cachedText = [text retain];
+-      cachedTextModiff = modiff;
++      cachedTextModiff = chars_modiff;
+       cachedTextStart = start;
+ 
+       if (visibleRuns)
+-- 
+2.43.0
+