From b03e5c1ad74fae38b6b491b970ee5c7877fec0be Mon Sep 17 00:00:00 2001
From: PatR <rankin@nethack.org>
Date: Fri, 10 Nov 2023 15:43:02 -0800
Subject: [PATCH] ^G of unseen monster

I used ^G to create a monster and specified "invisible owlbear".  I
then got "An owlbear appears next to you."  Except it didn't; it was
invisible and I lacked see-invisible.  I imagine that newsym() was
called for the new-yet-invisible monster, but that remained buffered
and was gone overridden by the time pending map update got flushed
at some point after the monster was made invisible.

Add a new makemon() flag to turn a newly created monster invisible
during its creation, before "monster appears" message is delivered.
Since that message will now be suppressed in this situation, use the
cursor-flash hack that indicates where the new, unseen monster got
placed.  Creating "1000 invisible <mon>" is something you probably
won't do twice.
---
 include/hack.h |  1 +
 src/makemon.c  |  2 ++
 src/read.c     | 16 ++++++----------
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/include/hack.h b/include/hack.h
index 8cd0b0e17..7fb80fd24 100644
--- a/include/hack.h
+++ b/include/hack.h
@@ -1043,6 +1043,7 @@ typedef uint32_t mmflags_nht;     /* makemon MM_ flags */
 #define GP_CHECKSCARY 0x200000L /* check monster for onscary() */
 #define MM_NOEXCLAM   0x400000L /* more sedate "<mon> appears." mesg for ^G */
 #define MM_IGNORELAVA 0x800000L /* ignore lava when positioning */
+#define MM_MINVIS   0x01000000L /* for ^G/create_particular */
 
 /* flags for make_corpse() and mkcorpstat(); 0..7 are recorded in obj->spe */
 #define CORPSTAT_NONE     0x00
diff --git a/src/makemon.c b/src/makemon.c
index e21986cf2..046290810 100644
--- a/src/makemon.c
+++ b/src/makemon.c
@@ -1270,6 +1270,8 @@ makemon(
     mtmp->mcansee = mtmp->mcanmove = TRUE;
     mtmp->seen_resistance = M_SEEN_NOTHING;
     mtmp->mpeaceful = (mmflags & MM_ANGRY) ? FALSE : peace_minded(ptr);
+    if ((mmflags & MM_MINVIS) != 0) /* for ^G */
+        mon_set_minvis(mtmp); /* call after place_monster() */
 
     switch (ptr->mlet) {
     case S_MIMIC:
diff --git a/src/read.c b/src/read.c
index cfa04c0d6..22eaef058 100644
--- a/src/read.c
+++ b/src/read.c
@@ -3160,6 +3160,9 @@ create_particular_creation(
             /* whichpm = rndmonst(); */
             /* mmflags |= (d->fem == FEMALE) ? MM_FEMALE : MM_MALE; */
         }
+        if (d->invisible)
+            mmflags |= MM_MINVIS;
+
         mtmp = makemon(whichpm, u.ux, u.uy, mmflags);
         if (!mtmp) {
             /* quit trying if creation failed and is going to repeat */
@@ -3181,24 +3184,17 @@ create_particular_creation(
 
             put_saddle_on_mon(otmp, mtmp);
         }
-        if (d->invisible) {
-            mon_set_minvis(mtmp);
-            if (does_block(mx, my, &levl[mx][my]))
-                block_point(mx, my);
-            else
-                unblock_point(mx, my);
-        }
-       if (d->hidden
+        if (d->hidden
            && ((is_hider(mtmp->data) && mtmp->data->mlet != S_MIMIC)
                || (hides_under(mtmp->data) && OBJ_AT(mx, my))
                || (mtmp->data->mlet == S_EEL && is_pool(mx, my))))
             mtmp->mundetected = 1;
         if (d->sleeping)
             mtmp->msleeping = 1;
-        /* iff asking for 'hidden', show location of every created monster
+        /* if asking for 'hidden', show location of every created monster
            that can't be seen--whether that's due to successfully hiding
            or vision issues (line-of-sight, invisibility, blindness) */
-        if (d->hidden && !canspotmon(mtmp)) {
+        if ((d->hidden || d->invisible) && !canspotmon(mtmp)) {
             int count = couldsee(mx, my) ? 8 : 4;
             char saveviz = gv.viz_array[my][mx];