feat: save the mount item as live did

Every live save had <mnt a="..."/>, which
LWOMountControlComponent::LoadFromSaveData (0x00bf99c0) reads as the
character's mount item (0 on the 450 saves looked at). The server wrote
no such element.

MountControlComponent now writes it: the item of the mount being ridden,
0 on foot. The saved value is read and kept; nothing is mounted from it,
as riding does not go on over a world change. A save from before gains
<mnt a="0"/> and nothing else in it changes.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

dGame/dComponents/CMakeLists.txt

@@ -16,6 +16,7 @@ set(DGAME_DCOMPONENTS_SOURCES
 	"Character/LevelProgressionComponent.cpp"
 	"LUPExhibitComponent.cpp"
 	"Character/MissionComponent.cpp"
+	"Character/MountControlComponent.cpp"
 	"MissionOfferComponent.cpp"
 	"ModelComponent.cpp"
 	"ModuleAssemblyComponent.cpp"

dGame/dComponents/Character/MountControlComponent.cpp

@@ -0,0 +1,23 @@
+#include "MountControlComponent.h"
+
+#include "Entity.h"
+#include "PossessorComponent.h"
+
+#include "tinyxml2.h"
+
+void MountControlComponent::LoadFromSaveData(const tinyxml2::XMLDocument& doc) {
+	const auto* const obj = doc.FirstChildElement("obj");
+	const auto* const mount = obj ? obj->FirstChildElement("mnt") : nullptr;
+	if (mount) mount->QueryInt64Attribute("a", &m_SavedMountItemID);
+}
+
+void MountControlComponent::WriteSaveData(tinyxml2::XMLDocument& doc) {
+	auto* const obj = doc.FirstChildElement("obj");
+	if (!obj) return;
+
+	auto* mount = obj->FirstChildElement("mnt");
+	if (!mount) mount = obj->InsertNewChildElement("mnt");
+
+	const auto* const possessor = m_Parent->GetComponent<PossessorComponent>();
+	mount->SetAttribute("a", possessor ? possessor->GetMountItemID() : LWOOBJID_EMPTY);
+}

dGame/dComponents/Character/MountControlComponent.h

@@ -2,17 +2,31 @@
 #define MOUNTCONTROLCOMPONENT_H
 
 #include "Component.h"
+#include "dCommonVars.h"
 #include "eReplicaComponentType.h"
 
 /**
  * Mount control (111): the character's riding of mounts, as the client's LWOMountControlComponent: the client makes it (componentID -1) with every character
- * (LWOCharacterComponent::Factory). Nothing of it is sent or done on the server yet.
+ * (LWOCharacterComponent::Factory). It keeps the mount item in the character's save, as live did (<mnt a="item id"/>,
+ * 0 when not riding: all 450 live saves looked at were 0).
  */
 class MountControlComponent final : public Component {
 public:
 	static constexpr eReplicaComponentType ComponentType = eReplicaComponentType::MOUNT_CONTROL;
 
 	MountControlComponent(Entity* parent, const int32_t componentID) : Component(parent, componentID) {}
+
+	// LWOMountControlComponent::LoadFromSaveData (0x00bf99c0): <mnt a>, the mount item of the save
+	void LoadFromSaveData(const tinyxml2::XMLDocument& doc) override;
+
+	// Writes <mnt a>: the item of the mount being ridden (PossessorComponent's), 0 when on foot
+	void WriteSaveData(tinyxml2::XMLDocument& doc) override;
+
+	// The mount item the save named. Riding does not go on over a world change, so nothing is mounted from it.
+	LWOOBJID GetSavedMountItemID() const { return m_SavedMountItemID; }
+
+private:
+	LWOOBJID m_SavedMountItemID = LWOOBJID_EMPTY;
 };
 
 #endif // MOUNTCONTROLCOMPONENT_H

tests/dGameTests/dComponentsTests/CMakeLists.txt

@@ -6,6 +6,7 @@ set(DCOMPONENTS_TESTS
 	"DestroyableLevelConfigTests.cpp"
 	"ProximityMonitorComponentTests.cpp"
 	"RailActivatorComponentTests.cpp"
+	"MountControlComponentTests.cpp"
 	"ConstructionOnlyComponentTests.cpp"
 	"PropertyVendorComponentTests.cpp"
 	"VendorBuybackTests.cpp"

tests/dGameTests/dComponentsTests/MountControlComponentTests.cpp

@@ -0,0 +1,62 @@
+// The mount item in a character's save: LWOMountControlComponent::LoadFromSaveData (0x00bf99c0) reads <mnt a>, and
+// every live save had the element (<mnt a="0"/> on the 450 looked at).
+#include "GameDependencies.h"
+
+#include "Entity.h"
+#include "MountControlComponent.h"
+#include "PossessorComponent.h"
+
+#include "tinyxml2.h"
+
+#include <gtest/gtest.h>
+#include <string>
+
+class MountControlComponentTests : public GameDependenciesTest {
+protected:
+	void SetUp() override { SetUpDependencies(); }
+	void TearDown() override { TearDownDependencies(); }
+
+	static std::string Print(const tinyxml2::XMLDocument& doc) {
+		tinyxml2::XMLPrinter printer(nullptr, true);
+		doc.Print(&printer);
+		return printer.CStr();
+	}
+};
+
+// A save from before the element was written gains it, and nothing else changes
+TEST_F(MountControlComponentTests, OldSaveGainsTheElement) {
+	tinyxml2::XMLDocument doc;
+	ASSERT_EQ(doc.Parse(R"(<obj v="1"><mf hc="1"/><char cc="5"/><dest hm="4"/></obj>)"), tinyxml2::XML_SUCCESS);
+	Entity player(70, info);
+	auto* const mountControl = player.AddComponent<MountControlComponent>(-1);
+	mountControl->LoadFromSaveData(doc);
+	EXPECT_EQ(mountControl->GetSavedMountItemID(), LWOOBJID_EMPTY);
+	mountControl->WriteSaveData(doc);
+	EXPECT_EQ(Print(doc), R"(<obj v="1"><mf hc="1"/><char cc="5"/><dest hm="4"/><mnt a="0"/></obj>)");
+	// Saving again changes nothing
+	mountControl->WriteSaveData(doc);
+	EXPECT_EQ(Print(doc), R"(<obj v="1"><mf hc="1"/><char cc="5"/><dest hm="4"/><mnt a="0"/></obj>)");
+}
+
+// The item of the mount being ridden is saved, in the element's own place; on foot it is 0 again
+TEST_F(MountControlComponentTests, TheRiddenMountIsSaved) {
+	tinyxml2::XMLDocument doc;
+	ASSERT_EQ(doc.Parse(R"(<obj v="1"><mis/><mnt a="1152921510436607007"/><dest hm="4"/></obj>)"), tinyxml2::XML_SUCCESS);
+	Entity player(71, info);
+	auto* const possessor = player.AddComponent<PossessorComponent>(-1);
+	auto* const mountControl = player.AddComponent<MountControlComponent>(-1);
+	mountControl->LoadFromSaveData(doc);
+	EXPECT_EQ(mountControl->GetSavedMountItemID(), 1152921510436607007LL);
+
+	// Nothing is ridden after a load
+	mountControl->WriteSaveData(doc);
+	EXPECT_EQ(Print(doc), R"(<obj v="1"><mis/><mnt a="0"/><dest hm="4"/></obj>)");
+
+	possessor->SetMountItemID(1152921510436607123LL);
+	mountControl->WriteSaveData(doc);
+	EXPECT_EQ(Print(doc), R"(<obj v="1"><mis/><mnt a="1152921510436607123"/><dest hm="4"/></obj>)");
+
+	possessor->SetMountItemID(LWOOBJID_EMPTY);
+	mountControl->WriteSaveData(doc);
+	EXPECT_EQ(Print(doc), R"(<obj v="1"><mis/><mnt a="0"/><dest hm="4"/></obj>)");
+}