Compute monster toHit on the fly

Source/loadsave.cpp

@@ -237,6 +237,7 @@ public:
 struct MonsterConversionData {
 	int8_t monsterLevel;
 	uint16_t experience;
+	uint8_t toHit;
 	uint8_t toHitSpecial;
 };
 
@@ -678,16 +679,18 @@ void LoadMonster(LoadHelper *file, Monster &monster, MonsterConversionData *mons
 	else
 		file->Skip(2); // Skip exp - now calculated from monstdat when the monster dies
 
-	if (monster.isPlayerMinion()) // Don't skip for golems
+	if (monsterConversionData != nullptr)
-		monster.toHit = file->NextLE<uint8_t>();
+		monsterConversionData->toHit = file->NextLE<uint8_t>();
+	else if (monster.isPlayerMinion()) // Don't skip for golems
+		monster.golemToHit = file->NextLE<uint8_t>();
 	else
-		file->Skip(1); // Skip hit as it's already initialized
+		file->Skip(1); // Skip toHit - now calculated on the fly
 	monster.minDamage = file->NextLE<uint8_t>();
 	monster.maxDamage = file->NextLE<uint8_t>();
 	if (monsterConversionData != nullptr)
 		monsterConversionData->toHitSpecial = file->NextLE<uint8_t>();
 	else
-		file->Skip(1); // Skip toHitSpecial as it's already initialized
+		file->Skip(1); // Skip toHitSpecial - now calculated on the fly
 	monster.minDamageSpecial = file->NextLE<uint8_t>();
 	monster.maxDamageSpecial = file->NextLE<uint8_t>();
 	monster.armorClass = file->NextLE<uint8_t>();
@@ -1472,7 +1475,10 @@ void SaveMonster(SaveHelper *file, Monster &monster, MonsterConversionData *mons
 	else
 		file->WriteLE<uint16_t>(static_cast<uint16_t>(std::min<unsigned>(std::numeric_limits<uint16_t>::max(), monster.exp(sgGameInitInfo.nDifficulty))));
 
-	file->WriteLE<uint8_t>(static_cast<uint8_t>(std::min<uint16_t>(monster.toHit, std::numeric_limits<uint8_t>::max()))); // For backwards compatibility
+	if (monsterConversionData != nullptr)
+		file->WriteLE<uint8_t>(monsterConversionData->toHit);
+	else
+		file->WriteLE<uint8_t>(static_cast<uint8_t>(std::min<uint16_t>(monster.toHit(sgGameInitInfo.nDifficulty), std::numeric_limits<uint8_t>::max()))); // For backwards compatibility
 	file->WriteLE<uint8_t>(monster.minDamage);
 	file->WriteLE<uint8_t>(monster.maxDamage);
 	if (monsterConversionData != nullptr)

Source/missiles.cpp

@@ -1003,7 +1003,7 @@ bool PlayerMHit(Player &player, Monster *monster, int dist, int mind, int maxd,
 	if (missileData.isArrow()) {
 		int tac = player.GetArmor();
 		if (monster != nullptr) {
-			hper = monster->toHit
+			hper = monster->toHit(sgGameInitInfo.nDifficulty)
 			    + ((monster->level(sgGameInitInfo.nDifficulty) - player.getCharacterLevel()) * 2)
 			    + 30
 			    - (dist * 2) - tac;

Source/monster.cpp

@@ -178,7 +178,6 @@ void InitMonster(Monster &monster, Direction rd, size_t typeIndex, Point positio
 	monster.rndItemSeed = AdvanceRndSeed();
 	monster.aiSeed = AdvanceRndSeed();
 	monster.whoHit = 0;
-	monster.toHit = monster.data().toHit;
 	monster.minDamage = monster.data().minDamage;
 	monster.maxDamage = monster.data().maxDamage;
 	monster.minDamageSpecial = monster.data().minDamageSpecial;
@@ -204,7 +203,6 @@ void InitMonster(Monster &monster, Direction rd, size_t typeIndex, Point positio
 		else
 			monster.maxHitPoints += 100 << 6;
 		monster.hitPoints = monster.maxHitPoints;
-		monster.toHit += NightmareToHitBonus;
 		monster.minDamage = 2 * (monster.minDamage + 2);
 		monster.maxDamage = 2 * (monster.maxDamage + 2);
 		monster.minDamageSpecial = 2 * (monster.minDamageSpecial + 2);
@@ -217,7 +215,6 @@ void InitMonster(Monster &monster, Direction rd, size_t typeIndex, Point positio
 		else
 			monster.maxHitPoints += 200 << 6;
 		monster.hitPoints = monster.maxHitPoints;
-		monster.toHit += HellToHitBonus;
 		monster.minDamage = 4 * monster.minDamage + 6;
 		monster.maxDamage = 4 * monster.maxDamage + 6;
 		monster.minDamageSpecial = 4 * monster.minDamageSpecial + 6;
@@ -1221,17 +1218,17 @@ void MonsterAttackEnemy(Monster &monster, int hit, int minDam, int maxDam)
 bool MonsterAttack(Monster &monster)
 {
 	if (monster.animInfo.currentFrame == monster.data().animFrameNum - 1) {
-		MonsterAttackEnemy(monster, monster.toHit, monster.minDamage, monster.maxDamage);
+		MonsterAttackEnemy(monster, monster.toHit(sgGameInitInfo.nDifficulty), monster.minDamage, monster.maxDamage);
 		if (monster.ai != MonsterAIID::Snake)
 			PlayEffect(monster, MonsterSound::Attack);
 	}
 	if (IsAnyOf(monster.type().type, MT_NMAGMA, MT_YMAGMA, MT_BMAGMA, MT_WMAGMA) && monster.animInfo.currentFrame == 8) {
-		MonsterAttackEnemy(monster, monster.toHit + 10, monster.minDamage - 2, monster.maxDamage - 2);
+		MonsterAttackEnemy(monster, monster.toHit(sgGameInitInfo.nDifficulty) + 10, monster.minDamage - 2, monster.maxDamage - 2);
 
 		PlayEffect(monster, MonsterSound::Attack);
 	}
 	if (IsAnyOf(monster.type().type, MT_STORM, MT_RSTORM, MT_STORML, MT_MAEL) && monster.animInfo.currentFrame == 12) {
-		MonsterAttackEnemy(monster, monster.toHit - 20, monster.minDamage + 4, monster.maxDamage + 4);
+		MonsterAttackEnemy(monster, monster.toHit(sgGameInitInfo.nDifficulty) - 20, monster.minDamage + 4, monster.maxDamage + 4);
 
 		PlayEffect(monster, MonsterSound::Attack);
 	}
@@ -3229,15 +3226,6 @@ tl::expected<void, std::string> PrepareUniqueMonst(Monster &monster, UniqueMonst
 	RETURN_IF_ERROR(InitTRNForUniqueMonster(monster));
 	monster.uniqTrans = uniquetrans++;
 
-	if (uniqueMonsterData.customToHit != 0) {
-		monster.toHit = uniqueMonsterData.customToHit;
-
-		if (sgGameInitInfo.nDifficulty == DIFF_NIGHTMARE) {
-			monster.toHit += NightmareToHitBonus;
-		} else if (sgGameInitInfo.nDifficulty == DIFF_HELL) {
-			monster.toHit += HellToHitBonus;
-		}
-	}
 	if (uniqueMonsterData.customArmorClass != 0) {
 		monster.armorClass = uniqueMonsterData.customArmorClass;
 
@@ -4656,7 +4644,7 @@ void SpawnGolem(Player &player, Monster &golem, Point position, Missile &missile
 	golem.maxHitPoints = 2 * (320 * missile._mispllvl + player._pMaxMana / 3);
 	golem.hitPoints = golem.maxHitPoints;
 	golem.armorClass = 25;
-	golem.toHit = 5 * (missile._mispllvl + 8) + 2 * player.getCharacterLevel();
+	golem.golemToHit = 5 * (missile._mispllvl + 8) + 2 * player.getCharacterLevel();
 	golem.minDamage = 2 * (missile._mispllvl + 4);
 	golem.maxDamage = 2 * (missile._mispllvl + 8);
 	golem.flags |= MFLAG_GOLEM;
@@ -4827,6 +4815,25 @@ MonsterMode Monster::getVisualMonsterMode() const
 	return MonsterMode::Petrified;
 }
 
+unsigned int Monster::toHit(_difficulty difficulty) const
+{
+	if (isPlayerMinion())
+		return golemToHit;
+
+	unsigned int baseToHit = data().toHit;
+	if (isUnique() && UniqueMonstersData[static_cast<size_t>(uniqueType)].customToHit != 0) {
+		baseToHit = UniqueMonstersData[static_cast<size_t>(uniqueType)].customToHit;
+	}
+
+	if (difficulty == DIFF_NIGHTMARE) {
+		baseToHit += NightmareToHitBonus;
+	} else if (difficulty == DIFF_HELL) {
+		baseToHit += HellToHitBonus;
+	}
+
+	return baseToHit;
+}
+
 unsigned int Monster::toHitSpecial(_difficulty difficulty) const
 {
 	unsigned int baseToHitSpecial = data().toHitSpecial;

Source/monster.h

@@ -222,7 +222,7 @@ struct Monster { // note: missing field _mAFNum
 	uint32_t rndItemSeed;
 	/** Seed used to determine AI behaviour/sync sounds in multiplayer games? */
 	uint32_t aiSeed;
-	uint16_t toHit;
+	uint16_t golemToHit;
 	uint16_t resistance;
 	_speech_id talkMsg;
 
@@ -364,6 +364,14 @@ struct Monster { // note: missing field _mAFNum
 		return monsterExp;
 	}
 
+	/**
+	 * @brief Calculates monster's chance to hit with normal attack.
+	 * Fetches base value from @p MonstersData array or @p UniqueMonstersData.
+	 * @param difficulty - difficulty on which calculation is performed
+	 * @return Monster's chance to hit with normal attack, including bonuses from difficulty and monster being unique
+	 */
+	unsigned int toHit(_difficulty difficulty) const;
+
 	/**
 	 * @brief Calculates monster's chance to hit with special attack.
 	 * Fetches base value from @p MonstersData array or @p UniqueMonstersData.