Add possibility to easier override HP and breath engine logic by Lua (#14179)

Co-authored-by: Lars Mueller <appgurulars@gmx.de>

doc/lua_api.md

@@ -8495,6 +8495,14 @@ child will follow movement and rotation of that bone.
     * Result is a table with the same fields as `light_definition` in `set_lighting`.
 * `respawn()`: Respawns the player using the same mechanism as the death screen,
   including calling `on_respawnplayer` callbacks.
+* `get_flags()`: returns a table of player flags (the following boolean fields):
+  * `breathing`: Whether breathing (regaining air) is enabled, default `true`.
+  * `drowning`: Whether drowning (losing air) is enabled, default `true`.
+  * `node_damage`: Whether the player takes damage from nodes, default `true`.
+* `set_flags(flags)`: sets flags
+  * takes a table in the same format as returned by `get_flags`
+  * absent fields are left unchanged
+
 
 `PcgRandom`
 -----------

src/script/common/c_content.cpp

@@ -291,7 +291,7 @@ const std::array<const char *, 33> object_property_keys = {
 	"use_texture_alpha",
 	"shaded",
 	"damage_texture_modifier",
-	"show_on_minimap"
+	"show_on_minimap",
 };
 
 /******************************************************************************/

src/script/lua_api/l_object.cpp

@@ -2688,6 +2688,41 @@ int ObjectRef::l_respawn(lua_State *L)
 	return 1;
 }
 
+// set_flags(self, flags)
+int ObjectRef::l_set_flags(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+	ObjectRef *ref = checkObject<ObjectRef>(L, 1);
+	auto *psao = getplayersao(ref);
+	if (psao == nullptr)
+		return 0;
+	if (!lua_istable(L, -1))
+		throw LuaError("expected a table of flags");
+	auto &flags = psao->m_flags;
+	flags.drowning = getboolfield_default(L, -1, "drowning", flags.drowning);
+	flags.breathing = getboolfield_default(L, -1, "breathing", flags.breathing);
+	flags.node_damage = getboolfield_default(L, -1, "node_damage", flags.node_damage);
+	return 0;
+}
+
+// get_flags(self)
+int ObjectRef::l_get_flags(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+	ObjectRef *ref = checkObject<ObjectRef>(L, 1);
+	const auto *psao = getplayersao(ref);
+	if (psao == nullptr)
+		return 0;
+	lua_createtable(L, 0, 3);
+	lua_pushboolean(L, psao->m_flags.drowning);
+	lua_setfield(L, -2, "drowning");
+	lua_pushboolean(L, psao->m_flags.breathing);
+	lua_setfield(L, -2, "breathing");
+	lua_pushboolean(L, psao->m_flags.node_damage);
+	lua_setfield(L, -2, "node_damage");
+	return 1;
+}
+
 
 ObjectRef::ObjectRef(ServerActiveObject *object):
 	m_object(object)
@@ -2838,6 +2873,8 @@ luaL_Reg ObjectRef::methods[] = {
 	luamethod(ObjectRef, set_lighting),
 	luamethod(ObjectRef, get_lighting),
 	luamethod(ObjectRef, respawn),
+	luamethod(ObjectRef, set_flags),
+	luamethod(ObjectRef, get_flags),
 
 	{0,0}
 };

src/script/lua_api/l_object.h

@@ -411,4 +411,10 @@ private:
 
 	// respawn(self)
 	static int l_respawn(lua_State *L);
+
+	// set_flags(self, flags)
+	static int l_set_flags(lua_State *L);
+	
+	// get_flags(self)
+	static int l_get_flags(lua_State *L);
 };

src/server/player_sao.cpp

@@ -156,7 +156,10 @@ void PlayerSAO::getStaticData(std::string * result) const
 
 void PlayerSAO::step(float dtime, bool send_recommended)
 {
-	if (!isImmortal() && m_drowning_interval.step(dtime, 2.0f)) {
+	bool not_immortal = !isImmortal();
+
+	if (not_immortal && m_flags.drowning
+			&& m_drowning_interval.step(dtime, 2.0f)) {
 		// Get nose/mouth position, approximate with eye position
 		v3s16 p = floatToInt(getEyePosition(), BS);
 		MapNode n = m_env->getMap().getNode(p);
@@ -174,7 +177,8 @@ void PlayerSAO::step(float dtime, bool send_recommended)
 		}
 	}
 
-	if (m_breathing_interval.step(dtime, 0.5f) && !isImmortal()) {
+	if (not_immortal && m_flags.breathing
+			&& m_breathing_interval.step(dtime, 0.5f)) {
 		// Get nose/mouth position, approximate with eye position
 		v3s16 p = floatToInt(getEyePosition(), BS);
 		MapNode n = m_env->getMap().getNode(p);
@@ -185,7 +189,8 @@ void PlayerSAO::step(float dtime, bool send_recommended)
 			setBreath(m_breath + 1);
 	}
 
-	if (!isImmortal() && m_node_hurt_interval.step(dtime, 1.0f)) {
+	if (not_immortal && m_flags.node_damage
+			&& m_node_hurt_interval.step(dtime, 1.0f)) {
 		u32 damage_per_second = 0;
 		std::string nodename;
 		v3s16 node_pos;

src/server/player_sao.h

@@ -228,6 +228,12 @@ private:
 	SimpleMetadata m_meta;
 
 public:
+	struct {
+		bool breathing : 1;
+		bool drowning : 1;
+		bool node_damage : 1;
+	} m_flags = {true, true, true};
+
 	bool m_physics_override_sent = false;
 };