Return by value from CCamera::BuildCameraRay

Some return values can be assigned to a `const auto`, somewhere `dir` is
mutated so the whole result has to be assigned to a non `const` variable
and once only dir is used, so structured binding isn't used there.

source/graphics/Camera.cpp

@@ -198,7 +198,7 @@ CCamera::Quad CCamera::GetViewQuad(const float dist) const
 	}};
 }
 
-void CCamera::BuildCameraRay(int px, int py, CVector3D& origin, CVector3D& dir) const
+CCamera::Ray CCamera::BuildCameraRay(const int px, const int py) const
 {
 	ENSURE(m_ProjType == ProjectionType::PERSPECTIVE || m_ProjType == ProjectionType::ORTHO);
 
@@ -216,19 +216,21 @@ void CCamera::BuildCameraRay(int px, int py, CVector3D& origin, CVector3D& dir)
 	const CVector3D basisX = points[1] - points[0];
 	const CVector3D basisY = points[3] - points[0];
 
+	Ray result;
 	if (m_ProjType == ProjectionType::PERSPECTIVE)
 	{
 		// Build direction for the camera origin to the target point.
-		origin = m_Orientation.GetTranslation();
+		result.origin = m_Orientation.GetTranslation();
 		CVector3D targetPoint = points[0] + (basisX * dx) + (basisY * dy);
-		dir = targetPoint - origin;
+		result.direction = targetPoint - result.origin;
 	}
 	else if (m_ProjType == ProjectionType::ORTHO)
 	{
-		origin = m_Orientation.GetTranslation() + (basisX * (dx - 0.5f)) + (basisY * (dy - 0.5f));
-		dir = m_Orientation.GetIn();
+		result.origin = m_Orientation.GetTranslation() + (basisX * (dx - 0.5f)) + (basisY * (dy - 0.5f));
+		result.direction = m_Orientation.GetIn();
 	}
-	dir.Normalize();
+	result.direction.Normalize();
+	return result;
 }
 
 void CCamera::GetScreenCoordinates(const CVector3D& world, float& x, float& y) const
@@ -247,9 +249,9 @@ CVector3D CCamera::GetWorldCoordinates(int px, int py, bool aboveWater) const
 {
 	CHFTracer tracer(g_Game->GetWorld()->GetTerrain());
 	int x, z;
-	CVector3D origin, dir, delta, terrainPoint, waterPoint;
+	CVector3D delta, terrainPoint, waterPoint;
 
-	BuildCameraRay(px, py, origin, dir);
+	const auto [origin, dir] = BuildCameraRay(px, py);
 
 	bool gotTerrain = tracer.RayIntersect(origin, dir, x, z, terrainPoint);
 
@@ -315,9 +317,9 @@ CVector3D CCamera::GetWorldCoordinates(int px, int py, float h) const
 	CPlane plane;
 	plane.Set(CVector3D(0.f, 1.f, 0.f), CVector3D(0.f, h, 0.f)); // upwards normal, passes through h
 
-	CVector3D origin, dir, delta, currentTarget;
+	CVector3D delta, currentTarget;
 
-	BuildCameraRay(px, py, origin, dir);
+	const auto [origin, dir] = BuildCameraRay(px, py);
 
 	if (plane.FindRayIntersection(origin, dir, &currentTarget))
 		return currentTarget;

source/graphics/Camera.h

@@ -87,7 +87,12 @@ class CCamera
 
 		// Builds a ray passing through the screen coordinate (px, py), calculates
 		// origin and direction of the ray.
-		void BuildCameraRay(int px, int py, CVector3D& origin, CVector3D& dir) const;
+		struct Ray
+		{
+			CVector3D origin;
+			CVector3D direction;
+		};
+		Ray BuildCameraRay(const int px, const int py) const;
 
 		// General helpers that seem to fit here
 

source/graphics/tests/test_Camera.h

@@ -335,8 +335,8 @@ public:
 			);
 			camera.SetPerspectiveProjection(1.0f, 101.0f, DEGTORAD(90.0f));
 
-			CVector3D origin, dir;
-			camera.BuildCameraRay(viewPort.m_Width / 2, viewPort.m_Height / 2, origin, dir);
+			const auto [origin, dir] =
+				camera.BuildCameraRay(viewPort.m_Width / 2, viewPort.m_Height / 2);
 			const CVector3D expectedOrigin = cameraPosition;
 			const CVector3D expectedDir = cameraDirection;
 			CompareVectors(origin, expectedOrigin, EPS);
@@ -365,8 +365,8 @@ public:
 			);
 			camera.SetOrthoProjection(2.0f, 128.0f, 10.0f);
 
-			CVector3D origin, dir;
-			camera.BuildCameraRay(viewPort.m_Width / 2, viewPort.m_Height / 2, origin, dir);
+			const auto [origin, dir] =
+				camera.BuildCameraRay(viewPort.m_Width / 2, viewPort.m_Height / 2);
 			const CVector3D expectedOrigin = cameraPosition;
 			const CVector3D expectedDir = cameraDirection;
 			CompareVectors(origin, expectedOrigin, EPS);

source/ps/TouchInput.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2019 Wildfire Games.
+/* Copyright (C) 2024 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -137,8 +137,7 @@ void CTouchInput::OnFingerMotion(int id, int x, int y)
 	if (m_State == STATE_PANNING && id == 0)
 	{
 		CCamera& camera = *(g_Game->GetView()->GetCamera());
-		CVector3D origin, dir;
-		camera.BuildCameraRay(x, y, origin, dir);
+		auto [origin, dir] = camera.BuildCameraRay(x, y);
 		dir *= m_PanDist / dir.Y;
 		camera.GetOrientation().Translate(m_PanFocus - dir - origin);
 		camera.UpdateFrustum();
@@ -151,8 +150,7 @@ void CTouchInput::OnFingerMotion(int id, int x, int y)
 		float zoomDist = (newDist - oldDist) * -0.005f * m_PanDist;
 
 		CCamera& camera = *(g_Game->GetView()->GetCamera());
-		CVector3D origin, dir;
-		camera.BuildCameraRay(m_Pos[0].X, m_Pos[0].Y, origin, dir);
+		CVector3D dir{camera.BuildCameraRay(m_Pos[0].X, m_Pos[0].Y).direction};
 		dir *= zoomDist;
 		camera.GetOrientation().Translate(dir);
 		camera.UpdateFrustum();

source/simulation2/helpers/Selection.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2022 Wildfire Games.
+/* Copyright (C) 2024 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -36,8 +36,7 @@
 entity_id_t EntitySelection::PickEntityAtPoint(CSimulation2& simulation, const CCamera& camera, int screenX, int screenY, player_id_t player, bool allowEditorSelectables)
 {
 	PROFILE2("PickEntityAtPoint");
-	CVector3D origin, dir;
-	camera.BuildCameraRay(screenX, screenY, origin, dir);
+	const auto [origin, dir] = camera.BuildCameraRay(screenX, screenY);
 
 	CmpPtr<ICmpUnitRenderer> cmpUnitRenderer(simulation.GetSimContext().GetSystemEntity());
 	ENSURE(cmpUnitRenderer);

source/tools/atlas/GameInterface/Handlers/CameraCtrlHandlers.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2023 Wildfire Games.
+/* Copyright (C) 2024 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -114,10 +114,9 @@ MESSAGEHANDLER(Scroll)
 	}
 	else if (msg->type == eScrollType::TO)
 	{
-		CVector3D origin, dir;
 		float x, y;
 		msg->pos->GetScreenSpace(x, y);
-		g_Game->GetView()->GetCamera()->BuildCameraRay((int)x, (int)y, origin, dir);
+		auto [origin, dir] = g_Game->GetView()->GetCamera()->BuildCameraRay((int)x, (int)y);
 		dir *= targetDistance;
 		camera.Translate(targetPos - dir - origin);
 		g_Game->GetView()->GetCamera()->UpdateFrustum();