From f02944f5a1ad18ceed4ae40a0fbbdddc981b4893 Mon Sep 17 00:00:00 2001
From: Gerd Moellmann <gerd.moellmann@gmail.com>
Date: Tue, 21 Jun 2022 15:49:44 +0200
Subject: [PATCH] Prevent GC of window referenced from EmacsScroller

* src/nsterm.m (EmacsScroller.mark, mark_nsterm): New functions.
* src/nsterm.h (EmacsScroller.mark, mark_nsterm): Declare.
* src/alloc.c (garbage_collect) [MAVE_NS]: Call mark_nsterm.
(Bug#56095)

(cherry picked from commit 5f1bd872478927ad4bc635502e74628d39885286)
---
 src/alloc.c  |  5 +++++
 src/nsterm.h |  4 ++++
 src/nsterm.m | 30 ++++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+)

diff --git a/src/alloc.c b/src/alloc.c
index 5ad80973949..1fe5b8f3fbd 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -6145,6 +6145,11 @@ garbage_collect (void)
   mark_fringe_data ();
 #endif
 
+
+#ifdef HAVE_NS
+  mark_nsterm ();
+#endif
+
   /* Everything is now marked, except for the data in font caches,
      undo lists, and finalizers.  The first two are compacted by
      removing an items which aren't reachable otherwise.  */
diff --git a/src/nsterm.h b/src/nsterm.h
index 911539844a0..4cfed109827 100644
--- a/src/nsterm.h
+++ b/src/nsterm.h
@@ -683,6 +683,7 @@ typedef id instancetype;
    int em_whole;
    }
 
+- (void) mark;
 - (instancetype) initFrame: (NSRect )r window: (Lisp_Object)win;
 - (void)setFrame: (NSRect)r;
 
@@ -1347,4 +1348,7 @@ enum NSWindowTabbingMode
 #define NSControlStateValueOff NSOffState
 #define NSBezelStyleRounded NSRoundedBezelStyle
 #endif
+
+extern void mark_nsterm (void);
+
 #endif	/* HAVE_NS */
diff --git a/src/nsterm.m b/src/nsterm.m
index 40540c47be1..1643ba5427c 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -9039,6 +9039,16 @@ -(bool)judge
   return ret;
 }
 
+- (void) mark
+{
+  if (window)
+    {
+      Lisp_Object win;
+      XSETWINDOW (win, window);
+      mark_object (win);
+    }
+}
+
 
 - (void)resetCursorRects
 {
@@ -9780,6 +9790,26 @@ Convert an X font name (XLFD) to an NS font name.
   return ret;
 }
 
+void
+mark_nsterm (void)
+{
+  NSTRACE ("mark_nsterm");
+  Lisp_Object tail, frame;
+  FOR_EACH_FRAME (tail, frame)
+    {
+      struct frame *f = XFRAME (frame);
+      if (FRAME_NS_P (f))
+	{
+	  NSArray *subviews = [[FRAME_NS_VIEW (f) superview] subviews];
+	  for (int i = [subviews count] - 1; i >= 0; --i)
+	    {
+	      id scroller = [subviews objectAtIndex: i];
+	      if ([scroller isKindOfClass: [EmacsScroller class]])
+                  [scroller mark];
+	    }
+	}
+    }
+}
 
 void
 syms_of_nsterm (void)