From 5e25d79beef19c39537b0f15982a175fec45bb3e Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 11 Nov 2023 17:37:57 +0000
Subject: Refactor BufferedLocationT to use a callback

Simplifies customisation in the face of multiple fields
---
 game/vehicles/railVehicle.cpp | 15 ++++++++++++---
 game/vehicles/railVehicle.h   |  5 ++---
 gfx/gl/bufferedLocation.cpp   |  7 ++++++-
 gfx/gl/bufferedLocation.h     | 18 +++++++-----------
 4 files changed, 27 insertions(+), 18 deletions(-)

diff --git a/game/vehicles/railVehicle.cpp b/game/vehicles/railVehicle.cpp
index fc43995..1ed904d 100644
--- a/game/vehicles/railVehicle.cpp
+++ b/game/vehicles/railVehicle.cpp
@@ -12,10 +12,19 @@
 #include <ray.h>
 
 RailVehicle::RailVehicle(RailVehicleClassPtr rvc) :
-	RailVehicleClass::Instance {rvc->instances.acquire()}, rvClass {std::move(rvc)}, location {&LV::body, *this},
+	RailVehicleClass::Instance {rvc->instances.acquire()}, rvClass {std::move(rvc)},
+	location {[this](const BufferedLocation * l) {
+		this->get()->body = l->getTransform();
+	}},
 	bogies {{
-			{&LV::front, *this, Position3D {0, rvClass->wheelBase / 2.F, 0}},
-			{&LV::back, *this, Position3D {0, -rvClass->wheelBase / 2.F, 0}},
+			{[this](const BufferedLocation * l) {
+				 this->get()->front = l->getTransform();
+			 },
+					Position3D {0, rvClass->wheelBase / 2.F, 0}},
+			{[this](const BufferedLocation * l) {
+				 this->get()->back = l->getTransform();
+			 },
+					Position3D {0, -rvClass->wheelBase / 2.F, 0}},
 	}}
 {
 }
diff --git a/game/vehicles/railVehicle.h b/game/vehicles/railVehicle.h
index e034852..20d1ea1 100644
--- a/game/vehicles/railVehicle.h
+++ b/game/vehicles/railVehicle.h
@@ -21,9 +21,8 @@ public:
 
 	RailVehicleClassPtr rvClass;
 	using LV = RailVehicleClass::LocationVertex;
-	using BLocation = BufferedLocationT<glm::mat4 LV::*, RailVehicleClass::Instance &>;
-	BLocation location;
-	std::array<BLocation, 2> bogies;
+	BufferedLocationUpdater location;
+	std::array<BufferedLocationUpdater, 2> bogies;
 };
 
 using RailVehiclePtr = std::unique_ptr<RailVehicle>;
diff --git a/gfx/gl/bufferedLocation.cpp b/gfx/gl/bufferedLocation.cpp
index 6ba8812..412e3ab 100644
--- a/gfx/gl/bufferedLocation.cpp
+++ b/gfx/gl/bufferedLocation.cpp
@@ -1,6 +1,5 @@
 #include "bufferedLocation.h"
 #include "location.h"
-#include "maths.h"
 #include <glm/gtx/transform.hpp>
 
 BufferedLocation::BufferedLocation(Position3D p, Rotation3D r) : BufferedLocation {Location {p, r}} { }
@@ -69,3 +68,9 @@ BufferedLocation::getRotationTransform() const
 {
 	return loc.getRotationTransform();
 }
+
+void
+BufferedLocationUpdater::updateBuffer() const
+{
+	onUpdate(this);
+}
diff --git a/gfx/gl/bufferedLocation.h b/gfx/gl/bufferedLocation.h
index 8302b3c..a5cd23e 100644
--- a/gfx/gl/bufferedLocation.h
+++ b/gfx/gl/bufferedLocation.h
@@ -4,7 +4,7 @@
 #include <functional>
 #include <glm/mat4x4.hpp>
 #include <glm/vec3.hpp>
-#include <tuple>
+#include <utility>
 
 class BufferedLocation {
 public:
@@ -26,16 +26,16 @@ public:
 	[[nodiscard]] glm::mat4 getRotationTransform() const;
 
 private:
-	virtual void updateBuffer() = 0;
+	virtual void updateBuffer() const = 0;
 
 	Location loc;
 };
 
-template<typename... Target> class BufferedLocationT : public BufferedLocation {
+class BufferedLocationUpdater : public BufferedLocation {
 public:
 	template<typename... LocationArgs>
-	BufferedLocationT(Target &&... target, LocationArgs &&... t) :
-		BufferedLocation {std::forward<LocationArgs>(t)...}, target {std::forward<Target>(target)...}
+	BufferedLocationUpdater(std::function<void(const BufferedLocation *)> onUpdate, LocationArgs &&... t) :
+		BufferedLocation {std::forward<LocationArgs>(t)...}, onUpdate {std::move(onUpdate)}
 	{
 		updateBuffer();
 	}
@@ -43,11 +43,7 @@ public:
 	using BufferedLocation::operator=;
 
 private:
-	void
-	updateBuffer() override
-	{
-		std::apply(std::invoke<const Target &...>, target) = getTransform();
-	}
+	void updateBuffer() const override;
 
-	std::tuple<Target...> target;
+	std::function<void(const BufferedLocation *)> onUpdate;
 };
-- 
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