From 402d2959cc569ebe740f07687c37283323fce314 Mon Sep 17 00:00:00 2001
From: Martin Sukany <martin@sukany.cz>
Date: Sat, 28 Feb 2026 22:08:55 +0100
Subject: [PATCH] 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.

* src/nsterm.h (EmacsView): Add lastZoomCursorRect ivar.
* src/nsterm.m (ns_draw_window_cursor): Store cursor rect in
lastZoomCursorRect; call UAZoomChangeFocus with CG-space
coordinates when UAZoomEnabled returns true.
(ns_update_end): Call UAZoomChangeFocus as fallback after each
redisplay cycle to ensure Zoom tracks cursor across window
switches (C-x o) where the physical cursor may not be redrawn.

Coordinate conversion: EmacsView pixels (AppKit, flipped) ->
NSWindow -> NSScreen -> CGRect with y-flip for CoreGraphics
top-left origin.  UAZoomChangeFocus is available since macOS 10.4
(ApplicationServices umbrella framework).

Tested on macOS 14 with Zoom enabled: cursor tracking works across
window splits, switches, and normal navigation.
---
 etc/NEWS     |  8 ++++++
 src/nsterm.h |  4 +++
 src/nsterm.m | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+)

diff --git a/etc/NEWS b/etc/NEWS
index ef36df5..e80e124 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -82,6 +82,14 @@ other directory on your system.  You can also invoke the
 
 * Changes in Emacs 31.1
 
++++
+** The macOS NS port now integrates with macOS Zoom.
+When macOS Zoom is enabled (System Settings -> Accessibility -> Zoom ->
+Follow keyboard focus), Emacs informs Zoom of the text cursor position
+after every cursor redraw via 'UAZoomChangeFocus'.  The zoomed viewport
+automatically tracks the insertion point across window splits and
+switches.
+
 +++
 ** 'line-spacing' now supports specifying spacing above the line.
 Previously, only spacing below the line could be specified.  The user
diff --git a/src/nsterm.h b/src/nsterm.h
index 7c1ee4c..f2755e4 100644
--- a/src/nsterm.h
+++ b/src/nsterm.h
@@ -484,6 +484,10 @@ enum ns_return_frame_mode
 @public
   struct frame *emacsframe;
   int scrollbarsNeedingUpdate;
+#ifdef NS_IMPL_COCOA
+  /* Cached cursor rect for macOS Zoom integration.  */
+  NSRect lastZoomCursorRect;
+#endif
   NSRect ns_userRect;
 }
 
diff --git a/src/nsterm.m b/src/nsterm.m
index 74e4ad5..eb1649b 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -1104,6 +1104,34 @@ static NSRect constrain_frame_rect(NSRect frameRect, bool isFullscreen)
 
   unblock_input ();
   ns_updating_frame = NULL;
+
+#ifdef NS_IMPL_COCOA
+  /* Zoom fallback: ensure Zoom tracks the cursor after window
+     switches (C-x o) and other operations where the physical cursor
+     may not be redrawn but the focused window changed.  This uses
+     lastZoomCursorRect which was set by ns_draw_window_cursor
+     during the current or a previous redisplay cycle.  */
+#if defined (MAC_OS_X_VERSION_MIN_REQUIRED) \
+    && MAC_OS_X_VERSION_MIN_REQUIRED >= 101000
+  if (view && UAZoomEnabled ()
+      && !NSIsEmptyRect (view->lastZoomCursorRect))
+    {
+      NSRect r = view->lastZoomCursorRect;
+      NSRect windowRect = [view convertRect:r toView:nil];
+      NSRect screenRect
+	= [[view window] convertRectToScreen:windowRect];
+      CGRect cgRect = NSRectToCGRect (screenRect);
+
+      CGFloat primaryH
+	= [[[NSScreen screens] firstObject] frame].size.height;
+      cgRect.origin.y
+	= primaryH - cgRect.origin.y - cgRect.size.height;
+
+      UAZoomChangeFocus (&cgRect, &cgRect,
+			 kUAZoomFocusTypeInsertionPoint);
+    }
+#endif /* MAC_OS_X_VERSION_MIN_REQUIRED >= 101000 */
+#endif /* NS_IMPL_COCOA */
 }
 
 static void
@@ -3232,6 +3260,48 @@ Note that CURSOR_WIDTH is meaningful only for (h)bar cursors.
   /* Prevent the cursor from being drawn outside the text area.  */
   r = NSIntersectionRect (r, ns_row_rect (w, glyph_row, TEXT_AREA));
 
+#ifdef NS_IMPL_COCOA
+  /* Accessibility: store cursor rect for macOS Zoom integration.
+     Zoom (System Settings -> Accessibility -> Zoom) tracks a focus
+     element to keep the zoomed viewport centered on the cursor.
+     UAZoomChangeFocus() informs Zoom of the cursor position after
+     every physical cursor redraw.
+
+     The coordinate conversion chain:
+       EmacsView pixels (AppKit, flipped, origin at top-left)
+         -> NSWindow coordinates (convertRect:toView:nil)
+         -> NSScreen coordinates (convertRectToScreen:)
+         -> CGRect (NSRectToCGRect, same values)
+         -> CG y-flip (CoreGraphics uses top-left origin on
+            the primary screen; AppKit uses bottom-left).  */
+  {
+    EmacsView *view = FRAME_NS_VIEW (f);
+    if (view && on_p && active_p)
+      {
+	view->lastZoomCursorRect = r;
+
+#if defined (MAC_OS_X_VERSION_MIN_REQUIRED) \
+    && MAC_OS_X_VERSION_MIN_REQUIRED >= 101000
+	if (UAZoomEnabled ())
+	  {
+	    NSRect windowRect = [view convertRect:r toView:nil];
+	    NSRect screenRect
+	      = [[view window] convertRectToScreen:windowRect];
+	    CGRect cgRect = NSRectToCGRect (screenRect);
+
+	    CGFloat primaryH
+	      = [[[NSScreen screens] firstObject] frame].size.height;
+	    cgRect.origin.y
+	      = primaryH - cgRect.origin.y - cgRect.size.height;
+
+	    UAZoomChangeFocus (&cgRect, &cgRect,
+			       kUAZoomFocusTypeInsertionPoint);
+	  }
+#endif /* MAC_OS_X_VERSION_MIN_REQUIRED >= 101000 */
+      }
+  }
+#endif /* NS_IMPL_COCOA */
+
   ns_focus (f, NULL, 0);
 
   NSGraphicsContext *ctx = [NSGraphicsContext currentContext];
-- 
2.43.0