WIP for #2936

template_mod.diff

diff --git a/binaries/data/mods/public/simulation/templates/units/rome_infantry_swordsman_a.xml b/binaries/data/mods/public/simulation/templates/units/rome_infantry_swordsman_a.xml
index 743ada5..77c0c44 100644
--- a/binaries/data/mods/public/simulation/templates/units/rome_infantry_swordsman_a.xml
+++ b/binaries/data/mods/public/simulation/templates/units/rome_infantry_swordsman_a.xml
@@ -7,7 +7,7 @@
   </Armour>
   <Attack>
     <Melee>
-      <Hack>14</Hack>
+      <Hack method="add">14.0</Hack>
     </Melee>
     <Charge>
       <Hack>28.0</Hack>
diff --git a/source/simulation2/system/ComponentManager.cpp b/source/simulation2/system/ComponentManager.cpp
index 4c7d35b..2b91b7f 100644
--- a/source/simulation2/system/ComponentManager.cpp
+++ b/source/simulation2/system/ComponentManager.cpp
@@ -1085,6 +1085,9 @@ std::string CComponentManager::GenerateSchema()
 	std::string schema =
 		"<grammar xmlns='http://relaxng.org/ns/structure/1.0' xmlns:a='http://ns.wildfiregames.com/entity' datatypeLibrary='http://www.w3.org/2001/XMLSchema-datatypes'>"
 			"<define name='nonNegativeDecimal'>"
+				"<optional>"
+					"<attribute name='method'><data type='string'/></attribute>"
+				"</optional>"
 				"<data type='decimal'><param name='minInclusive'>0</param></data>"
 			"</define>"
 			"<define name='positiveDecimal'>"
diff --git a/source/simulation2/system/ParamNode.cpp b/source/simulation2/system/ParamNode.cpp
index f966004..203a39c 100644
--- a/source/simulation2/system/ParamNode.cpp
+++ b/source/simulation2/system/ParamNode.cpp
@@ -78,11 +78,18 @@ void CParamNode::ApplyLayer(const XMBFile& xmb, const XMBElement& element, const
 
 	bool hasSetValue = false;
 
-	// Look for special attributes
 	int at_disable = xmb.GetAttributeID("disable");
 	int at_replace = xmb.GetAttributeID("replace");
+	int at_method = xmb.GetAttributeID("method");
 	int at_datatype = xmb.GetAttributeID("datatype");
 	bool replacing = false;
+	enum method {
+		ADD,
+		SUB,
+		MUL,
+		DIV,
+		INVALID
+	} method = INVALID;
 	{
 		XERO_ITER_ATTR(element, attr)
 		{
@@ -96,6 +103,19 @@ void CParamNode::ApplyLayer(const XMBFile& xmb, const XMBElement& element, const
 				m_Childs.erase(name);
 				replacing = true;
 			}
+			else if (attr.Name == at_method)
+			{
+				if (std::wstring(attr.Value.begin(), attr.Value.end()) == L"add")
+					method = ADD;
+				else if (std::wstring(attr.Value.begin(), attr.Value.end()) == L"sub")
+					method = SUB;
+				else if (std::wstring(attr.Value.begin(), attr.Value.end()) == L"mul")
+					method = MUL;
+				else if (std::wstring(attr.Value.begin(), attr.Value.end()) == L"div")
+					method = DIV;
+				else
+					LOGERROR(L"Invalid method '%ls'", attr.Value.c_str());
+			}
 		}
 	}
 	{
@@ -142,6 +162,26 @@ void CParamNode::ApplyLayer(const XMBFile& xmb, const XMBElement& element, const
 
 	// Add this element as a child node
 	CParamNode& node = m_Childs[name];
+	if (method != INVALID)
+	{
+		// TODO switch over supported types (int and fixed basically); log errors in other cases
+		fixed oldval = node.ToFixed();
+		fixed mod = fixed::FromString(CStrW(value));
+		switch (method)
+		{
+		case SUB: mod = -mod;
+		case ADD:
+			node.m_Value = (oldval + mod).ToString().FromUTF8();
+			hasSetValue = true;
+			break;
+		case MUL:
+			// TODO
+			break;
+		case DIV:
+			// TODO
+			break;
+		}
+	}
 	if (!hasSetValue)
 		node.m_Value = value;
 
@@ -155,7 +195,8 @@ void CParamNode::ApplyLayer(const XMBFile& xmb, const XMBElement& element, const
 	XERO_ITER_ATTR(element, attr)
 	{
 		// Skip special attributes
-		if (attr.Name == at_replace) continue;
+		if (attr.Name == at_replace || attr.Name == at_method)
+			continue;
 		// Add any others
 		std::string attrName = xmb.GetAttributeString(attr.Name);
 		node.m_Childs["@" + attrName].m_Value = attr.Value.FromUTF8();