Applying a spellbook hints about read charges left

Applying a spellbook allows the player to flip through the pages, providing an
indication of how many reads it has left before turning blank.

Originally from UnNetHack but code almost completely refactored and updated
for post 3.4 changes like deafness and novels.

doc/fixes37.0

@@ -68,6 +68,7 @@ add 'quick_farsight' option to provide some control over random clairvoyance
 	revealed map can seem intrusive; doesn't affect clairvoyance spell
 replace "money" in in-game texts with "gold"
 when hallucinating, see hallucinated currencies instead of bits for an ale
+applying a spellbook hints about read charges left
 
 
 Platform- and/or Interface-Specific New Features

src/apply.c

@@ -31,6 +31,7 @@ static int FDECL(use_pole, (struct obj *));
 static int FDECL(use_cream_pie, (struct obj *));
 static int FDECL(use_grapple, (struct obj *));
 static int FDECL(do_break_wand, (struct obj *));
+static int FDECL(flip_through_book, (struct obj *));
 static boolean FDECL(figurine_location_checks, (struct obj *,
                                                     coord *, BOOLEAN_P));
 static void FDECL(add_class, (char *, CHAR_P));
@@ -3520,7 +3521,8 @@ char class_list[];
 {
     register struct obj *otmp;
     int otyp;
-    boolean knowoil, knowtouchstone, addpotions, addstones, addfood;
+    boolean knowoil, knowtouchstone;
+    boolean addpotions, addstones, addfood, addspellbooks;
 
     knowoil = objects[POT_OIL].oc_name_known;
     knowtouchstone = objects[TOUCHSTONE].oc_name_known;
@@ -3539,6 +3541,8 @@ char class_list[];
             addstones = TRUE;
         if (otyp == CREAM_PIE || otyp == EUCALYPTUS_LEAF)
             addfood = TRUE;
+        if (otmp->oclass == SPBOOK_CLASS)
+            addspellbooks = TRUE;
     }
 
     class_list[0] = '\0';
@@ -3551,6 +3555,8 @@ char class_list[];
         add_class(class_list, GEM_CLASS);
     if (addfood)
         add_class(class_list, FOOD_CLASS);
+    if (addspellbooks)
+        add_class(class_list, SPBOOK_CLASS);
 }
 
 /* the 'a' command */
@@ -3576,6 +3582,9 @@ doapply()
     if (obj->oclass == WAND_CLASS)
         return do_break_wand(obj);
 
+    if (obj->oclass == SPBOOK_CLASS)
+        return flip_through_book(obj);
+
     switch (obj->otyp) {
     case BLINDFOLD:
     case LENSES:
@@ -3791,4 +3800,57 @@ boolean is_horn;
     return unfixable_trbl;
 }
 
+static int
+flip_through_book(obj)
+struct obj *obj;
+{
+    if (Underwater) {
+        pline("You don't want to get the pages even more soggy, do you?");
+        return 0;
+    }
+
+    You("flip through the pages of the spellbook.");
+
+    if (obj->otyp == SPE_BOOK_OF_THE_DEAD) {
+        if (Deaf) {
+            You_see("the pages glow faintly %s.", hcolor(NH_RED));
+        } else {
+            You_hear("the pages make an unpleasant %s sound.",
+                    Hallucination ? "chuckling"
+                                  : "rustling");
+        }
+        return 1;
+    } else if (Blind) {
+        pline("The pages feel %s.",
+              Hallucination ? "freshly picked"
+                            : "rough and dry");
+        return 1;
+    } else if (obj->otyp == SPE_BLANK_PAPER) {
+        pline("This spellbook %s.",
+              Hallucination ? "doesn't have much of a plot"
+                            : "has nothing written in it");
+        makeknown(obj->otyp);
+        return 1;
+    }
+
+    if (Hallucination) {
+        You("enjoy the animated initials.");
+    } else {
+        static const char* fadeness[] = {
+            "fresh",
+            "slightly faded",
+            "very faded",
+            "extremely faded",
+            "barely visible"
+        };
+
+        int index = min(obj->spestudied, MAX_SPELL_STUDY);
+        pline("The%s ink in this spellbook is %s.",
+              objects[obj->otyp].oc_magic ? " magical" : "",
+              fadeness[index]);
+    }
+
+    return 1;
+}
+
 /*apply.c*/