Enhance feedback from detect unseen

I was never too happy with how this was a silent effect that required
you to watch the map to see if anything changed. It might count as
an accessibility issue as well, not sure.

This change adds specific feedback for all the possible things that
might get revealed by detecting unseen. If you reveal a secret door or a
trap, you now get a message indicating that.

One slight behavior change here: if the only thing detected is invisible
monsters, the game previously did not return a result of "detected
a non-zero number of things" to the caller of findit(); now it does.
(This allows the wand to be automatically identified when it prints a
message about detecting invisible monsters.)

src/detect.c

@@ -35,6 +35,16 @@ static int reveal_terrain_getglyph(coordxy, coordxy, int, unsigned, int, int);
    that aren't used are compile-/link-/load-time initialized to 0 */
 static struct trap dummytrap;
 
+/* data for enhanced feedback from findone() */
+struct found_things {
+    uchar num_sdoors;
+    uchar num_scorrs;
+    uchar num_traps;
+    uchar num_mons;
+    uchar num_invis;
+    uchar num_cleared_invis;
+};
+
 /* wildcard class for clear_stale_map - this used to be used as a getobj()
    input but it's no longer used for that function */
 #define ALL_CLASSES (MAXOCLASSES + 1)
@@ -1542,7 +1552,7 @@ cvt_sdoor_to_door(struct rm *lev)
 /* find something at one location; it should find all somethings there
    since it is used for magical detection rather than physical searching */
 static void
-findone(coordxy zx, coordxy zy, genericptr_t num)
+findone(coordxy zx, coordxy zy, genericptr_t whatfound)
 {
     register struct trap *ttmp;
     register struct monst *mtmp;
@@ -1558,13 +1568,13 @@ findone(coordxy zx, coordxy zy, genericptr_t num)
         cvt_sdoor_to_door(&levl[zx][zy]); /* .typ = DOOR */
         magic_map_background(zx, zy, 0);
         newsym(zx, zy);
-        (*(int *) num)++;
+        ((struct found_things *) whatfound)->num_sdoors++;
     } else if (levl[zx][zy].typ == SCORR) {
         levl[zx][zy].typ = CORR;
         unblock_point(zx, zy);
         magic_map_background(zx, zy, 0);
         newsym(zx, zy);
-        (*(int *) num)++;
+        ((struct found_things *) whatfound)->num_scorrs++;
     }
 
     if ((ttmp = t_at(zx, zy)) != 0 && !ttmp->tseen
@@ -1572,7 +1582,7 @@ findone(coordxy zx, coordxy zy, genericptr_t num)
         && ttmp->ttyp != STATUE_TRAP) {
         ttmp->tseen = 1;
         newsym(zx, zy);
-        (*(int *) num)++;
+        ((struct found_things *) whatfound)->num_traps++;
     }
 
     if ((mtmp = m_at(zx, zy)) != 0
@@ -1580,18 +1590,20 @@ findone(coordxy zx, coordxy zy, genericptr_t num)
         && (!canspotmon(mtmp) || mtmp->mundetected || M_AP_TYPE(mtmp))) {
         if (M_AP_TYPE(mtmp)) {
             seemimic(mtmp);
-            (*(int *) num)++;
+            ((struct found_things *) whatfound)->num_mons++;
         } else if (mtmp->mundetected && (is_hider(mtmp->data)
                                          || hides_under(mtmp->data)
                                          || mtmp->data->mlet == S_EEL)) {
             mtmp->mundetected = 0;
             newsym(zx, zy);
-            (*(int *) num)++;
+            ((struct found_things *) whatfound)->num_mons++;
         }
-        if (!canspotmon(mtmp) && !glyph_is_invisible(levl[zx][zy].glyph))
+        if (!canspotmon(mtmp) && !glyph_is_invisible(levl[zx][zy].glyph)) {
             map_invisible(zx, zy);
+            ((struct found_things *) whatfound)->num_invis++;
+        }
     } else if (unmap_invisible(zx, zy)) {
-        (*(int *) num)++;
+        ((struct found_things *) whatfound)->num_cleared_invis++;
     }
 }
 
@@ -1662,10 +1674,41 @@ int
 findit(void)
 {
     int num = 0;
+    struct found_things found = {0};
 
     if (u.uswallow)
         return 0;
-    do_clear_area(u.ux, u.uy, BOLT_LIM, findone, (genericptr_t) &num);
+    do_clear_area(u.ux, u.uy, BOLT_LIM, findone, (genericptr_t) &found);
+
+    if (found.num_sdoors)
+        You("reveal %ssecret door%s!", found.num_sdoors == 1 ? "a " : "",
+            found.num_sdoors == 1 ? "" : "s");
+    num += found.num_sdoors;
+
+    if (found.num_scorrs)
+        You("reveal %ssecret corridor%s!", found.num_scorrs == 1 ? "a " : "",
+            found.num_scorrs == 1 ? "" : "s");
+    num += found.num_scorrs;
+
+    if (found.num_traps)
+        You("reveal %strap%s!", found.num_traps == 1 ? "a " : "",
+            found.num_traps == 1 ? "" : "s");
+    num += found.num_traps;
+
+    if (found.num_mons)
+        You("reveal %shidden monster%s!", found.num_mons == 1 ? "a " : "",
+            found.num_mons == 1 ? "" : "s");
+    num += found.num_mons;
+
+    if (found.num_invis)
+        You("detect %sinvisible monster%s!", found.num_invis == 1 ? "an " : "",
+            found.num_invis == 1 ? "" : "s");
+    num += found.num_invis;
+
+    if (!num && found.num_cleared_invis)
+        You_feel("less paranoid.");
+    num += found.num_cleared_invis;
+
     return num;
 }