Allow querying of the propagated light level.

This adds one Lua function, get_node_propagated_light, which works exactly
as get_node_light except that it excludes the entity at the specified location.

Class MapNode is extended to support this.

This allows extensions such as magic_lantern to work without removing the
object – each lamp would be removed prior to querying the light level then,
once the new setting had been determined, it would be re-created.
Unfortunately, this caused noticeable flicker...

The problem? The scene may be rendered while the lamp is removed.

src/mapnode.cpp

@@ -63,6 +63,39 @@ void MapNode::setLight(enum LightBank bank, u8 a_light, INodeDefManager *nodemgr
 		assert(0);
 }
 
+u8 MapNode::getPropagatedLight(enum LightBank bank, INodeDefManager *nodemgr) const
+{
+	const ContentFeatures &f = nodemgr->get(*this);
+	u8 light = 0;
+	if(f.param_type == CPT_LIGHT)
+	{
+		if(bank == LIGHTBANK_DAY)
+			light = param1 & 0x0f;
+		else if(bank == LIGHTBANK_NIGHT)
+			light = (param1>>4)&0x0f;
+		else
+			assert(0);
+	}
+	return light;
+}
+
+bool MapNode::getPropagatedLightBanks(u8 &lightday, u8 &lightnight, INodeDefManager *nodemgr) const
+{
+	const ContentFeatures &f = nodemgr->get(*this);
+	if(f.param_type == CPT_LIGHT)
+	{
+		lightday = param1 & 0x0f;
+		lightnight = (param1>>4)&0x0f;
+		return true;
+	}
+	else
+	{
+		lightday = 0;
+		lightnight = 0;
+		return false;
+	}
+}
+
 u8 MapNode::getLight(enum LightBank bank, INodeDefManager *nodemgr) const
 {
 	// Select the brightest of [light source, propagated light]

src/mapnode.h

@@ -150,9 +150,31 @@ struct MapNode
 	}
 	
 	void setLight(enum LightBank bank, u8 a_light, INodeDefManager *nodemgr);
+	u8 getPropagatedLight(enum LightBank bank, INodeDefManager *nodemgr) const;
+	bool getPropagatedLightBanks(u8 &lightday, u8 &lightnight, INodeDefManager *nodemgr) const;
 	u8 getLight(enum LightBank bank, INodeDefManager *nodemgr) const;
 	bool getLightBanks(u8 &lightday, u8 &lightnight, INodeDefManager *nodemgr) const;
 	
+	// 0 <= daylight_factor <= 1000
+	// 0 <= return value <= LIGHT_SUN
+	u8 getPropagatedLightBlend(u32 daylight_factor, INodeDefManager *nodemgr) const
+	{
+		u8 lightday = 0;
+		u8 lightnight = 0;
+		getPropagatedLightBanks(lightday, lightnight, nodemgr);
+		return blend_light(daylight_factor, lightday, lightnight);
+	}
+
+	// 0.0 <= daylight_factor <= 1.0
+	// 0 <= return value <= LIGHT_SUN
+	u8 getPropagatedLightBlendF1(float daylight_factor, INodeDefManager *nodemgr) const
+	{
+		u8 lightday = 0;
+		u8 lightnight = 0;
+		getPropagatedLightBanks(lightday, lightnight, nodemgr);
+		return blend_light_f1(daylight_factor, lightday, lightnight);
+	}
+
 	// 0 <= daylight_factor <= 1000
 	// 0 <= return value <= LIGHT_SUN
 	u8 getLightBlend(u32 daylight_factor, INodeDefManager *nodemgr) const

src/scriptapi.cpp

@@ -3773,10 +3773,8 @@ private:
 		}
 	}
 
-	// EnvRef:get_node_light(pos, timeofday)
-	// pos = {x=num, y=num, z=num}
-	// timeofday: nil = current time, 0 = night, 0.5 = day
-	static int l_get_node_light(lua_State *L)
+	// Internal light level code
+	static int l_get_node_light_internal(lua_State *L, bool propagated_only)
 	{
 		EnvRef *o = checkobject(L, 1);
 		ServerEnvironment *env = o->m_env;
@@ -3792,7 +3790,8 @@ private:
 		try{
 			MapNode n = env->getMap().getNode(pos);
 			INodeDefManager *ndef = env->getGameDef()->ndef();
-			lua_pushinteger(L, n.getLightBlend(dnr, ndef));
+			int level = propagated_only ? n.getPropagatedLightBlend(dnr, ndef) : n.getLightBlend(dnr, ndef);
+			lua_pushinteger(L, level);
 			return 1;
 		} catch(InvalidPositionException &e)
 		{
@@ -3801,6 +3800,22 @@ private:
 		}
 	}
 
+	// EnvRef:get_node_propagated_light(pos, timeofday)
+	// pos = {x=num, y=num, z=num}
+	// timeofday: nil = current time, 0 = night, 0.5 = day
+	static int l_get_node_propagated_light(lua_State *L)
+	{
+		return l_get_node_light_internal(L, true);
+	}
+
+	// EnvRef:get_node_light(pos, timeofday)
+	// pos = {x=num, y=num, z=num}
+	// timeofday: nil = current time, 0 = night, 0.5 = day
+	static int l_get_node_light(lua_State *L)
+	{
+		return l_get_node_light_internal(L, false);
+	}
+
 	// EnvRef:place_node(pos, node)
 	// pos = {x=num, y=num, z=num}
 	static int l_place_node(lua_State *L)
@@ -4321,6 +4336,7 @@ const luaL_reg EnvRef::methods[] = {
 	method(EnvRef, remove_node),
 	method(EnvRef, get_node),
 	method(EnvRef, get_node_or_nil),
+	method(EnvRef, get_node_propagated_light),
 	method(EnvRef, get_node_light),
 	method(EnvRef, place_node),
 	method(EnvRef, dig_node),