From 0ec2cec5fad1f5cb1aa048b49bb67bfe493785e6 Mon Sep 17 00:00:00 2001
From: Bardur Arantsson <bardur@scientician.net>
Date: Tue, 29 Mar 2016 20:32:55 +0200
Subject: Have RANDOM_{RESIST,POWER} avoid existing flags

---
 src/defines.h  |  3 ---
 src/object1.cc | 51 ++++++-------------------------------
 src/object2.cc | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++------
 3 files changed, 78 insertions(+), 55 deletions(-)

diff --git a/src/defines.h b/src/defines.h
index 519dc535..91d3065d 100644
--- a/src/defines.h
+++ b/src/defines.h
@@ -2247,9 +2247,6 @@
 /* High resist */
 #define EGO_XTRA_POWER          2
 
-/* Special ability */
-#define EGO_XTRA_ABILITY        3
-
 /*** Object flag values ***/
 
 
diff --git a/src/object1.cc b/src/object1.cc
index 78206f68..ae0317c7 100644
--- a/src/object1.cc
+++ b/src/object1.cc
@@ -850,40 +850,6 @@ static void object_flags_xtra(object_type const *o_ptr, u32b *f2, u32b *f3, u32b
 		break;
 	}
 	
-	case EGO_XTRA_ABILITY:
-	{
-		/* Choose an ability */
-		switch (o_ptr->xtra2 % 8)
-		{
-		case 0:
-			(*f3) |= (TR3_FEATHER);
-			break;
-		case 1:
-			(*f3) |= (TR3_LITE1);
-			break;
-		case 2:
-			(*f3) |= (TR3_SEE_INVIS);
-			break;
-		case 3:
-			(*esp) |= (ESP_ALL);
-			break;
-		case 4:
-			(*f3) |= (TR3_SLOW_DIGEST);
-			break;
-		case 5:
-			(*f3) |= (TR3_REGEN);
-			break;
-		case 6:
-			(*f2) |= (TR2_FREE_ACT);
-			break;
-		case 7:
-			(*f2) |= (TR2_HOLD_LIFE);
-			break;
-		}
-		
-		break;
-	}
-
 	}
 }
 
@@ -920,16 +886,13 @@ void object_flags(object_type const *o_ptr, u32b *f1, u32b *f2, u32b *f3, u32b *
 			apply_flags_set(o_ptr->name1, a_ptr->set, f1, f2, f3, f4, f5, esp);
 	}
 
-	/* Random artifact ! */
-	if (o_ptr->art_flags1 || o_ptr->art_flags2 || o_ptr->art_flags3 || o_ptr->art_flags4 || o_ptr->art_flags5 || o_ptr->art_esp)
-	{
-		(*f1) |= o_ptr->art_flags1;
-		(*f2) |= o_ptr->art_flags2;
-		(*f3) |= o_ptr->art_flags3;
-		(*f4) |= o_ptr->art_flags4;
-		(*f5) |= o_ptr->art_flags5;
-		(*esp) |= o_ptr->art_esp;
-	}
+	/* Mix in art_{flagsX,esp} */
+	(*f1) |= o_ptr->art_flags1;
+	(*f2) |= o_ptr->art_flags2;
+	(*f3) |= o_ptr->art_flags3;
+	(*f4) |= o_ptr->art_flags4;
+	(*f5) |= o_ptr->art_flags5;
+	(*esp) |= o_ptr->art_esp;
 
 	/* Extra powers */
 	if (!(o_ptr->art_name))
diff --git a/src/object2.cc b/src/object2.cc
index 145aab4c..18d0e980 100644
--- a/src/object2.cc
+++ b/src/object2.cc
@@ -2040,6 +2040,63 @@ static void object_mention(object_type *o_ptr)
 	}
 }
 
+static void random_artifact_power(object_type *o_ptr)
+{
+	// Shorthand
+	auto f2 = &o_ptr->art_flags2;
+	auto f3 = &o_ptr->art_flags3;
+	auto esp = &o_ptr->art_esp;
+
+	// Choose ability
+	auto try_choose = [&o_ptr, &f2, &f3, &esp](int choice) {
+		switch (choice)
+		{
+		case 0:
+			(*f3) |= (TR3_FEATHER);
+			break;
+		case 1:
+			(*f3) |= (TR3_LITE1);
+			break;
+		case 2:
+			(*f3) |= (TR3_SEE_INVIS);
+			break;
+		case 3:
+			(*esp) |= (ESP_ALL);
+			break;
+		case 4:
+			(*f3) |= (TR3_SLOW_DIGEST);
+			break;
+		case 5:
+			(*f3) |= (TR3_REGEN);
+			break;
+		case 6:
+			(*f2) |= (TR2_FREE_ACT);
+			break;
+		case 7:
+			(*f2) |= (TR2_HOLD_LIFE);
+			break;
+		}
+	};
+
+	// Save old values for comparison
+	u32b const old_f2 = *f2;
+	u32b const old_f3 = *f3;
+	u32b const old_esp = *esp;
+
+	// Choose an ability; make sure we choose one that isn't already chosen
+	for (int tries = 0; tries < 1000; tries++)
+	{
+		// Tentative choice
+		int choice = rand_int(8);
+		try_choose(choice);
+
+		// If there's any difference, then we chose a non-overlapping power.
+		if ((*f2 != old_f2) || (*f3 != old_f3) || (*esp != old_esp))
+		{
+			break;
+		}
+	}
+}
 
 void random_artifact_resistance(object_type * o_ptr)
 {
@@ -2063,20 +2120,26 @@ void random_artifact_resistance(object_type * o_ptr)
 	// Grant the resistance/power
 	if (give_power)
 	{
-		o_ptr->xtra1 = EGO_XTRA_ABILITY;
-
-		/* Randomize the "xtra" power */
-		if (o_ptr->xtra1)
-		{
-			o_ptr->xtra2 = randint(256);
-		}
+		random_artifact_power(o_ptr);
 	}
 
 	artifact_bias = 0;
 
 	if (give_resistance)
 	{
-		random_resistance(o_ptr, FALSE, ((randint(22)) + 16));
+		// Save resistance flags
+		u32b const f2 = o_ptr->art_flags2;
+		// We'll be a little generous here and make sure that the object
+		// gets a resistance that it doesn't actually already have.
+		for (int tries = 0; tries < 1000; tries++)
+		{
+			random_resistance(o_ptr, FALSE, ((randint(22)) + 16));
+			// Picked up a new resistance?
+			if (f2 != o_ptr->art_flags2)
+			{
+				break;
+			}
+		}
 	}
 }
 
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