Allow to disable display of line numbers beyond EOB

* src/buffer.c (disable_line_numbers_overlay_at_eob): New
function.
* src/lisp.h (disable_line_numbers_overlay_at_eob): Add prototype.
* src/xdisp.c (should_produce_line_number): When at ZV, call
disable_line_numbers_overlay_at_eob to determine whether line
numbers should be displayed beyond ZV.

3 files changed, 37 insertions, 4 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 80dbd3318dc..780e4d7a7d6 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -3054,6 +3054,33 @@ mouse_face_overlay_overlaps (Lisp_Object overlay)
   return i < n;
 }
 
+/* Return the value of the 'display-line-numbers-disable' property at
+   EOB, if there's an overlay at ZV with a non-nil value of that property.  */
+Lisp_Object
+disable_line_numbers_overlay_at_eob (void)
+{
+  ptrdiff_t n, i, size;
+  Lisp_Object *v, tem = Qnil;
+  Lisp_Object vbuf[10];
+  USE_SAFE_ALLOCA;
+
+  size = ARRAYELTS (vbuf);
+  v = vbuf;
+  n = overlays_in (ZV, ZV, 0, &v, &size, NULL, NULL);
+  if (n > size)
+    {
+      SAFE_NALLOCA (v, 1, n);
+      overlays_in (ZV, ZV, 0, &v, &n, NULL, NULL);
+    }
+
+  for (i = 0; i < n; ++i)
+    if ((tem = Foverlay_get (v[i], Qdisplay_line_numbers_disable),
+         !NILP (tem)))
+      break;
+
+  SAFE_FREE ();
+  return tem;
+}
 
 
 /* Fast function to just test if we're at an overlay boundary.  */
diff --git a/src/lisp.h b/src/lisp.h
index ff8dde2b825..f5cb6c75706 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -3965,6 +3965,7 @@ extern void syms_of_editfns (void);
 
 /* Defined in buffer.c.  */
 extern bool mouse_face_overlay_overlaps (Lisp_Object);
+extern Lisp_Object disable_line_numbers_overlay_at_eob (void);
 extern _Noreturn void nsberror (Lisp_Object);
 extern void adjust_overlays_for_insert (ptrdiff_t, ptrdiff_t);
 extern void adjust_overlays_for_delete (ptrdiff_t, ptrdiff_t);
diff --git a/src/xdisp.c b/src/xdisp.c
index c318a6954c4..7649b16e974 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -20948,10 +20948,15 @@ should_produce_line_number (struct it *it)
 #endif
 
   /* If the character at current position has a non-nil special
-     property, disable line numbers for this row.  */
-  Lisp_Object val = Fget_char_property (make_number (IT_CHARPOS (*it)),
-                                        Qdisplay_line_numbers_disable,
-                                        it->window);
+     property, disable line numbers for this row.  For ZV, we need to
+     use a special algorithm that only supports empty overlays at that
+     point, because get-char-property always returns nil for ZV.  */
+  Lisp_Object val = Qnil;
+  if (IT_CHARPOS (*it) >= ZV)
+    val = disable_line_numbers_overlay_at_eob ();
+  else
+    val = Fget_char_property (make_number (IT_CHARPOS (*it)),
+                              Qdisplay_line_numbers_disable, it->window);
   return NILP (val) ? true : false;
 }