Add minetest.register_on_player_hpchange

builtin/game/register.lua

@@ -407,6 +407,34 @@ local function make_registration_wrap(reg_fn_name, clear_fn_name)
 	return list
 end
 
+core.registered_on_player_hpchanges = { modifiers = { }, loggers = { } }
+function core.registered_on_player_hpchange(player, hp_change)
+	local last = false
+	for i = #core.registered_on_player_hpchanges.modifiers, 1, -1 do
+		local func = core.registered_on_player_hpchanges.modifiers[i]
+		hp_change, last = func(player, hp_change)
+		if type(hp_change) ~= "number" then
+			local debuginfo = debug.getinfo(func)
+			error("The register_on_hp_changes function has to return a number at " ..
+				debuginfo.short_src .. " line " .. debuginfo.linedefined)
+		end
+		if last then
+			break
+		end
+	end
+	for i, func in ipairs(core.registered_on_player_hpchanges.loggers) do
+		func(player, hp_change)
+	end
+	return hp_change
+end
+function core.register_on_player_hpchange(func, modifier)
+	if modifier then
+		table.insert(core.registered_on_player_hpchanges.modifiers, func)
+	else
+		table.insert(core.registered_on_player_hpchanges.loggers, func)
+	end
+end
+
 core.registered_biomes      = make_registration_wrap("register_biome",      "clear_registered_biomes")
 core.registered_ores        = make_registration_wrap("register_ore",        "clear_registered_ores")
 core.registered_decorations = make_registration_wrap("register_decoration", "clear_registered_decorations")

doc/lua_api.txt

@@ -1785,6 +1785,13 @@ Call these functions only at load time!
        the puncher to the punched.
      * `damage` - number that represents the damage calculated by the engine
      * should return `true` to prevent the default damage mechanism
+* `minetest.register_on_player_hpchange(func(player, hp_change), modifier)`
+    * Called when the player gets damaged or healed
+    * `player`: ObjectRef of the player
+    * `hp_change`: the amount of change. Negative when it is damage.
+    * `modifier`: when true, the function should return the actual hp_change.
+      Note: modifiers only get a temporary hp_change that can be modified by later modifiers.
+      modifiers can return true as a second argument to stop the execution of further functions.
 * `minetest.register_on_respawnplayer(func(ObjectRef))`
      * Called when player is to be respawned
      * Called _before_ repositioning of player occurs

src/content_sao.cpp

@@ -1125,6 +1125,12 @@ void PlayerSAO::setHP(s16 hp)
 {
 	s16 oldhp = m_player->hp;
 
+	s16 hp_change = m_env->getScriptIface()->on_player_hpchange(this,
+		hp - oldhp);
+	if (hp_change == 0)
+		return;
+	hp = oldhp + hp_change;
+
 	if (hp < 0)
 		hp = 0;
 	else if (hp > PLAYER_MAX_HP)

src/script/cpp_api/s_player.cpp

@@ -69,6 +69,25 @@ bool ScriptApiPlayer::on_punchplayer(ServerActiveObject *player,
 	return lua_toboolean(L, -1);
 }
 
+s16 ScriptApiPlayer::on_player_hpchange(ServerActiveObject *player,
+	s16 hp_change)
+{
+	SCRIPTAPI_PRECHECKHEADER
+
+	// Get core.registered_on_player_hpchange
+	lua_getglobal(L, "core");
+	lua_getfield(L, -1, "registered_on_player_hpchange");
+	lua_remove(L, -2);
+
+	objectrefGetOrCreate(L, player);
+	lua_pushnumber(L, hp_change);
+	if (lua_pcall(L, 2, 1, m_errorhandler))
+		scriptError();
+	hp_change = lua_tointeger(L, -1);
+	lua_pop(L, -1);
+	return hp_change;
+}
+
 bool ScriptApiPlayer::on_respawnplayer(ServerActiveObject *player)
 {
 	SCRIPTAPI_PRECHECKHEADER

src/script/cpp_api/s_player.h

@@ -43,6 +43,7 @@ public:
 	bool on_punchplayer(ServerActiveObject *player,
 		ServerActiveObject *hitter, float time_from_last_punch,
 		const ToolCapabilities *toolcap, v3f dir, s16 damage);
+	s16 on_player_hpchange(ServerActiveObject *player, s16 hp_change);
 	void on_playerReceiveFields(ServerActiveObject *player,
 		const std::string &formname, const StringMap &fields);
 };