From 59bad96d5fb6f12ce17039d94e42a26938297a40 Mon Sep 17 00:00:00 2001
From: Kp <kp@valhallalegends.com>
Date: Sun, 29 Jan 2017 21:02:48 +0000
Subject: [PATCH] Add back homing weapons cheat for D2

Kreator proposed restoring the Descent 2 cheat that grants homing
capability to all weapons.  This commit implements that proposition,
with some changes to the implementation details.

Based-on-patch-by: Chris Taylor <chris@icculus.org>
Requested-by: Chris Taylor <https://github.com/dxx-rebirth/dxx-rebirth/pull/318>
---
 common/main/fwd-weapon.h  |  3 +++
 common/main/game.h        |  1 +
 similar/main/game.cpp     |  5 +++++
 similar/main/gamecntl.cpp |  6 ++++++
 similar/main/gameseq.cpp  |  8 ++++++++
 similar/main/weapon.cpp   | 17 +++++++++++++++++
 6 files changed, 40 insertions(+)

diff --git a/common/main/fwd-weapon.h b/common/main/fwd-weapon.h
index 3d123b1ba..13c53579d 100644
--- a/common/main/fwd-weapon.h
+++ b/common/main/fwd-weapon.h
@@ -211,6 +211,9 @@ int attempt_to_steal_item(vobjptridx_t objp, vobjptr_t playerobjp);
 
 #define SMEGA_ID    40
 
+void weapons_homing_all();
+void weapons_homing_all_reset();
+
 extern void rock_the_mine_frame(void);
 extern void smega_rock_stuff(void);
 extern void init_smega_detonates(void);
diff --git a/common/main/game.h b/common/main/game.h
index a272c5169..4ab51c96f 100644
--- a/common/main/game.h
+++ b/common/main/game.h
@@ -333,6 +333,7 @@ struct game_cheats : prohibit_void_ptr<game_cheats>
 	int lamer;
 	int accessory;
 	int bouncyfire;
+	int homingfire;
 	int killallrobots;
 	int robotskillrobots;
 	int monsterdamage;
diff --git a/similar/main/game.cpp b/similar/main/game.cpp
index 4a948f993..f30dff921 100644
--- a/similar/main/game.cpp
+++ b/similar/main/game.cpp
@@ -1149,6 +1149,11 @@ int cheats_enabled()
 //turns off all cheats & resets cheater flag
 void game_disable_cheats()
 {
+#if defined(DXX_BUILD_DESCENT_II)
+	if (cheats.homingfire)
+		weapons_homing_all_reset();
+#endif
+
 	cheats = {};
 }
 
diff --git a/similar/main/gamecntl.cpp b/similar/main/gamecntl.cpp
index df6cf8276..d0e8f81b4 100644
--- a/similar/main/gamecntl.cpp
+++ b/similar/main/gamecntl.cpp
@@ -1405,6 +1405,7 @@ constexpr cheat_code cheat_codes[] = {
 	{ "rockrgrl", &game_cheats::fullautomap },
 	{ "wildfire", &game_cheats::rapidfire },
 	{ "duddaboo", &game_cheats::bouncyfire },
+	{ "lpnlizard", &game_cheats::homingfire },
 	{ "imagespace", &game_cheats::robotfiringsuspended },
 	{ "spaniard", &game_cheats::killallrobots },
 	{ "silkwing", &game_cheats::robotskillrobots },
@@ -1639,6 +1640,11 @@ static window_event_result FinalCheats()
 		
 		HUD_init_message(HM_DEFAULT, "Bouncing weapons %s!", cheats.bouncyfire?TXT_ON:TXT_OFF);
 	}
+
+	if (gotcha == &game_cheats::homingfire)
+	{
+		HUD_init_message(HM_DEFAULT, "Homing weapons %s!", cheats.homingfire ? (weapons_homing_all(), TXT_ON) : (weapons_homing_all_reset(), TXT_OFF));
+	}
 #endif
 
 	if (gotcha == &game_cheats::turbo)
diff --git a/similar/main/gameseq.cpp b/similar/main/gameseq.cpp
index 698cd43f5..a091075e6 100644
--- a/similar/main/gameseq.cpp
+++ b/similar/main/gameseq.cpp
@@ -1383,6 +1383,14 @@ static window_event_result AdvanceLevel(int secret_flag)
 
 #if defined(DXX_BUILD_DESCENT_II)
 	Assert(!secret_flag);
+
+	// Loading a level can write over homing_flag.
+	// So for simplicity, reset the homing weapon cheat here.
+	if (cheats.homingfire)
+	{
+		cheats.homingfire = 0;
+		weapons_homing_all_reset();
+	}
 #endif
 	if (Current_level_num != Last_level)
 	{
diff --git a/similar/main/weapon.cpp b/similar/main/weapon.cpp
index 5632aa724..2ec9dbef7 100644
--- a/similar/main/weapon.cpp
+++ b/similar/main/weapon.cpp
@@ -1013,6 +1013,23 @@ int pick_up_vulcan_ammo(player_info &player_info, uint_fast32_t ammo_count, cons
 }
 
 #if defined(DXX_BUILD_DESCENT_II)
+// Homing weapons cheat
+
+void weapons_homing_all()
+{
+	range_for(auto &&objp, vobjptr)
+		if (objp->type == OBJ_WEAPON)
+			objp->ctype.laser_info.track_goal = object_none;
+	range_for (auto &w, Weapon_info)
+		w.homing_flag |= 2;
+}
+
+void weapons_homing_all_reset()
+{
+	range_for (auto &w, Weapon_info)
+		w.homing_flag &= ~2;
+}
+
 #define	SMEGA_SHAKE_TIME		(F1_0*2)
 #define	MAX_SMEGA_DETONATES	4
 static array<fix64, MAX_SMEGA_DETONATES> Smega_detonate_times;