From 085a2c40d1335819b7a0d43b67581cc7b547088f Mon Sep 17 00:00:00 2001
From: Martin Sukany <martin@sukany.cz>
Date: Sat, 28 Feb 2026 22:39:35 +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 lastCursorRect, zoomCursorUpdated.
* src/nsterm.m (ns_draw_window_cursor): Store cursor rect in
lastCursorRect; call UAZoomChangeFocus with CG-space coordinates
when UAZoomEnabled returns true.  Set zoomCursorUpdated flag.
(ns_update_end): Call UAZoomChangeFocus as fallback when cursor
was not physically redrawn in this cycle (e.g., after C-x o window
switch).  Gated by zoomCursorUpdated to avoid double calls.

Coordinate conversion: EmacsView pixels (AppKit, flipped) ->
NSWindow -> NSScreen -> CGRect with y-flip for CoreGraphics
top-left origin.  UAZoomEnabled returns false when Zoom is inactive,
so overhead is a single function call per redisplay cycle.

Tested on macOS 14 with Zoom enabled: cursor tracking works across
window splits, switches (C-x o), and normal navigation.
---
 etc/NEWS     |  8 +++++++
 src/nsterm.h |  6 +++++
 src/nsterm.m | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+)

diff --git a/etc/NEWS b/etc/NEWS
index ef36df5..f10d17e 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..ea6e7ba 100644
--- a/src/nsterm.h
+++ b/src/nsterm.h
@@ -484,6 +484,12 @@ enum ns_return_frame_mode
 @public
   struct frame *emacsframe;
   int scrollbarsNeedingUpdate;
+#ifdef NS_IMPL_COCOA
+  /* Cached cursor rect for macOS Zoom integration.  Set by
+     ns_draw_window_cursor, used by ns_update_end fallback.  */
+  NSRect lastCursorRect;
+  BOOL zoomCursorUpdated;
+#endif
   NSRect ns_userRect;
 }
 
diff --git a/src/nsterm.m b/src/nsterm.m
index 74e4ad5..cd721c8 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -1104,6 +1104,35 @@ 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) where the physical cursor may not be redrawn.
+     Only fires when ns_draw_window_cursor did NOT run in this cycle
+     (zoomCursorUpdated is NO).  */
+#if defined (MAC_OS_X_VERSION_MIN_REQUIRED) \
+    && MAC_OS_X_VERSION_MIN_REQUIRED >= 101000
+  if (view && !view->zoomCursorUpdated && UAZoomEnabled ()
+      && !NSIsEmptyRect (view->lastCursorRect))
+    {
+      NSRect r = view->lastCursorRect;
+      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);
+    }
+  if (view)
+    view->zoomCursorUpdated = NO;
+#endif
+#endif /* NS_IMPL_COCOA */
 }
 
 static void
@@ -3232,6 +3261,45 @@ 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
+  /* Zoom integration: inform macOS Zoom of the cursor position.
+     Zoom (System Settings -> Accessibility -> Zoom) tracks a focus
+     element to keep the zoomed viewport centered on the cursor.
+
+     Coordinate conversion:
+       EmacsView pixels (AppKit, flipped, top-left origin)
+         -> NSWindow (convertRect:toView:nil)
+         -> NSScreen (convertRectToScreen:)
+         -> CGRect with y-flip for CoreGraphics top-left origin.  */
+  {
+    EmacsView *view = FRAME_NS_VIEW (f);
+    if (view && on_p && active_p)
+      {
+	view->lastCursorRect = r;
+	view->zoomCursorUpdated = YES;
+
+#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
+      }
+  }
+#endif /* NS_IMPL_COCOA */
+
   ns_focus (f, NULL, 0);
 
   NSGraphicsContext *ctx = [NSGraphicsContext currentContext];
-- 
2.43.0