From 23e2549bd2ce3c3180f0f9a5ead326bc0183c1fb Mon Sep 17 00:00:00 2001
From: Martin Sukany <martin@sukany.cz>
Date: Sat, 28 Feb 2026 14:16:29 +0100
Subject: [PATCH] ns: include overlay display strings in accessibility text

Completion frameworks like Vertico, Ivy, and Icomplete render
candidates via overlay before-string / after-string properties
rather than as buffer text.  The accessibility text extraction
in ns_ax_buffer_text only reads buffer content, making these
overlay-based UIs invisible to VoiceOver.

This patch adds two enhancements:

1. Walk overlays in the visible range after buffer text extraction
   and append their before-string / after-string content.  Each
   overlay string gets a virtual visible-run entry mapped to the
   overlay's buffer position for cursor tracking.

2. Detect overlay-only changes (BUF_OVERLAY_MODIFF) in the
   notification dispatch and fire AXValueChanged, so VoiceOver
   re-reads content when completion candidates change.

* src/nsterm.m (ns_ax_buffer_text): Append overlay before-string
and after-string content with virtual visible-run entries.
(EmacsAccessibilityBuffer postAccessibilityNotificationsForFrame:):
Check BUF_OVERLAY_MODIFF and fire postTextChangedNotification when
overlays change.

Tested on macOS 14 with VoiceOver and Vertico completion framework.
Verified: M-x candidate navigation announced, file finder candidates
read by VoiceOver when moving up/down.
---
 src/nsterm.m | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/src/nsterm.m b/src/nsterm.m
index 1780194..88458aa 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -7021,6 +7021,68 @@ ns_ax_buffer_text (struct window *w, ptrdiff_t *out_start,
       pos = run_end;
     }
 
+  /* Append overlay display strings (before-string, after-string).
+     Many completion frameworks (Vertico, Ivy, Icomplete) render
+     candidates via overlay properties rather than buffer text.
+     Without this, VoiceOver cannot read overlay-based content.
+
+     We append overlay strings after the buffer text and give each
+     a virtual run mapped to the overlay's buffer position, so cursor
+     tracking and index mapping remain functional.  */
+  {
+    Lisp_Object ov_list = Foverlays_in (make_fixnum (begv),
+					make_fixnum (zv));
+    for (Lisp_Object tail = ov_list; CONSP (tail); tail = XCDR (tail))
+      {
+	Lisp_Object ov = XCAR (tail);
+	Lisp_Object props[2];
+	ptrdiff_t anchors[2];
+
+	props[0] = Foverlay_get (ov, intern_c_string ("before-string"));
+	anchors[0] = XFIXNUM (Foverlay_start (ov));
+	props[1] = Foverlay_get (ov, intern_c_string ("after-string"));
+	anchors[1] = XFIXNUM (Foverlay_end (ov));
+
+	for (int k = 0; k < 2; k++)
+	  {
+	    if (!STRINGP (props[k]))
+	      continue;
+
+	    /* Cap total text.  */
+	    if (ax_offset >= NS_AX_TEXT_CAP)
+	      break;
+
+	    NSString *nsstr
+	      = [NSString stringWithLispString:props[k]];
+	    NSUInteger ns_len = [nsstr length];
+	    if (ns_len == 0)
+	      continue;
+
+	    if (ax_offset + ns_len > NS_AX_TEXT_CAP)
+	      ns_len = NS_AX_TEXT_CAP - ax_offset;
+
+	    if (ns_len < [nsstr length])
+	      nsstr = [nsstr substringToIndex:ns_len];
+
+	    [result appendString:nsstr];
+
+	    if (nruns >= run_capacity)
+	      {
+		run_capacity *= 2;
+		runs = xrealloc (runs, run_capacity
+				 * sizeof (ns_ax_visible_run));
+	      }
+	    runs[nruns].charpos = anchors[k];
+	    runs[nruns].length = 0;  /* virtual — no buffer chars */
+	    runs[nruns].ax_start = ax_offset;
+	    runs[nruns].ax_length = ns_len;
+	    nruns++;
+
+	    ax_offset += ns_len;
+	  }
+      }
+  }
+
   unbind_to (count, Qnil);
 
   *out_runs = runs;
@@ -8795,6 +8857,16 @@ ns_ax_completion_text_for_span (EmacsAccessibilityBuffer *elem,
       [self postTextChangedNotification:point];
     }
 
+  /* --- Overlay content changed (e.g. Vertico/Ivy candidate switch) ---
+     Overlay-only changes (before-string, after-string, display) bump
+     BUF_OVERLAY_MODIFF but not BUF_MODIFF.  Fire ValueChanged so
+     VoiceOver re-reads the buffer content including overlay strings.  */
+  else if (BUF_OVERLAY_MODIFF (b) != self.cachedOverlayModiff)
+    {
+      self.cachedOverlayModiff = BUF_OVERLAY_MODIFF (b);
+      [self postTextChangedNotification:point];
+    }
+
   /* --- Cursor moved or selection changed ---
      Use 'else if' — edits and selection moves are mutually exclusive
      per the WebKit/Chromium pattern.  */
-- 
2.43.0