Screen.cpp
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	#include <echo/Graphics/Scene.h>
	#include <echo/GUI/Screen.h>
	#include <echo/Graphics/RenderTarget.h>
	#include <echo/Graphics/Camera.h>
	#include <echo/Maths/Length.h>

	namespace Echo
	{
	namespace GUI
	{
	Screen::Screen() : mUpdateSizeToCamera(true)
	{
	}

	Screen::~Screen()
	{

	}

	Screen::Screen(const Screen& other)
	{
	*this = other;
	}

	Screen& Screen::operator=(const Screen& rhs)
	{
	Container::operator=(rhs);
	mUpdateSizeToCamera = rhs.mUpdateSizeToCamera;
	return *this;
	}

	shared_ptr<Element> Screen::_Clone() const
	{
	return shared_ptr<Element>(new Screen(*this));
	}

	void Screen::Accept(SceneRenderableVisitor& visitor)
	{
	if(mUpdateSizeToCamera)
	{
	const Camera* camera = visitor.GetCurrentCamera();

	if(camera)
	{
	Vector2 size;
	if(camera->GetProjectionType()==ProjectionTypes::PERSPECTIVE)
	{
	Scalar distance = GetDerivedPosition().Distance(camera->GetPosition());

	// Calculate so that the horizontal view takes up viewWidth units.
	Radian halfFOVx = camera->GetFOV() / 2.f;
	Scalar width = (Maths::Tan(halfFOVx.ValueRadians()) * distance) * 2.f;
	Scalar height = width / camera->GetAspectRatio();

	if(const RenderTarget* renderTarget = visitor.GetCurrentRenderTarget())
	{
	CalculateAndSetWorldUnits(renderTarget,Vector2(width,height));
	}

	size=Vector2(width,height);
	}else
	{
	size = Vector2(camera->GetOrthoWindowWidth(),camera->GetOrthoWindowHeight());
	}

	if(const RenderTarget* renderTarget = visitor.GetCurrentRenderTarget())
	{
	CalculateAndSetWorldUnits(renderTarget,size);
	}
	//The SetSize() function takes care of setting to the same size (i.e not causing an update)
	SetSize(size.x,size.y);
	}
	}
	SceneEntity::Accept(visitor);
	}

	void Screen::CalculateAndSetWorldUnits(const RenderTarget* renderTarget, Vector2 worldResolution)
	{
	//We need
	// RenderTarget X and Y resolution (pixels))
	// RenderTarget DPI (pixels per inch)
	// Viewport (percent of RenderTarget)
	// ViewportResolution (pixels))
	// Camera Near Frustum Plane Resolution (world units)
	Scalar xDPI = renderTarget->GetDisplayXDPI();
	Scalar yDPI = renderTarget->GetDisplayYDPI();
	if(xDPI==0.f \|\| yDPI==0.f)
	{
	return;
	}
	Scalar xResolution = renderTarget->GetWidth();
	Scalar yResolution = renderTarget->GetHeight();
	Viewport* viewport = renderTarget->GetCurrentViewport();
	Viewport::Rectangle vr = viewport->GetRectangle(renderTarget->GetAspectRatio());

	//Viewport Width is in DPI. We need to find the ratio between the world space (X) and the display space.
	Metre metresPerPixelX(Inch(1 / xDPI));
	Scalar viewportWidth = vr.GetWidth() * xResolution;
	Metre viewportPhysicalWidth(metresPerPixelX.Count() * viewportWidth);
	Scalar unitsPerMetreX = worldResolution.x / viewportPhysicalWidth.Count();
	//std::cout << "metresPerPixelX: " << metresPerPixelX.Count() << " viewportWidth: " << viewportWidth << " viewportPhysicalWidth: " << viewportPhysicalWidth.Count() << "m worldResolution.x:" << worldResolution.x << " unitsPerMetreX:" << unitsPerMetreX << std::endl;

	//Viewport Height is in DPI. We need to find the ratio between the world space (X) and the display space.
	Metre metresPerPixelY(Inch(1 / yDPI));
	Scalar viewportHeight = vr.GetWidth() * yResolution;
	Metre viewportPhysicalHeight(metresPerPixelY.Count() * viewportHeight);
	Scalar unitsPerMetreY = worldResolution.y / viewportPhysicalHeight.Count();

	SetPhysicalToWorldRatio(unitsPerMetreX,unitsPerMetreY);
	}

	Scalar Screen::GetNativeAspectRatio()
	{
	// This is a bit of an odd request because the size is always adjusted via the Accept method.
	// We'll just return 1. because this shouldn't really be a thing.
	// If the size mode is set to use this method then size is discarded anyhow so it isn't a problem.
	// We don't bother sending the calculated screen aspect ratio because the method isn't public so
	// it shouldn't be outside of its intended use.
	return 1.f;
	}
	}
	}

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