From cf1ac82da3cee849be60625c7387ef339741d246 Mon Sep 17 00:00:00 2001
From: Mitchell Richters <mjr4077au@gmail.com>
Date: Thu, 1 Dec 2022 21:46:50 +1100
Subject: [PATCH] - Set up interpolated camera angle changes to occur at
 framerate when all conditions in `P_NoInterpolation()` are met.

---
 src/playsim/d_player.h      |  4 +++
 src/playsim/p_mobj.cpp      | 63 +++++++++++++++++++++++++++++++------
 src/rendering/r_utility.cpp | 35 +++++++++++++++++++++
 3 files changed, 93 insertions(+), 9 deletions(-)

diff --git a/src/playsim/d_player.h b/src/playsim/d_player.h
index 2a64415fb..efaabdb9e 100644
--- a/src/playsim/d_player.h
+++ b/src/playsim/d_player.h
@@ -449,6 +449,10 @@ public:
 	void SetFOV(float fov);
 	bool HasWeaponsInSlot(int slot) const;
 	bool Resurrect();
+
+	// Scaled angle adjustment info. Not for direct manipulation.
+	DRotator angleTargets;
+	DRotator angleAppliedAmounts;
 };
 
 // Bookkeeping on players - state.
diff --git a/src/playsim/p_mobj.cpp b/src/playsim/p_mobj.cpp
index 1b4684b8c..1a4c65211 100644
--- a/src/playsim/p_mobj.cpp
+++ b/src/playsim/p_mobj.cpp
@@ -3427,10 +3427,25 @@ void AActor::SetPitch(DAngle p, int fflags)
 
 	if (p != Angles.Pitch)
 	{
-		Angles.Pitch = p;
-		if (player != nullptr && (fflags & SPF_INTERPOLATE))
+		if (player != nullptr)
 		{
-			player->cheats |= CF_INTERPVIEW;
+			if (fflags & SPF_INTERPOLATE)
+			{
+				if (P_NoInterpolation(player, this))
+				{
+					player->angleTargets.Pitch = deltaangle(Angles.Pitch, p);
+					player->angleAppliedAmounts.Pitch = nullAngle;
+				}
+				else
+				{
+					Angles.Pitch = p;
+					player->cheats |= CF_INTERPVIEW;
+				}
+			}
+		}
+		else
+		{
+			Angles.Pitch = p;
 		}
 	}
 	
@@ -3440,10 +3455,25 @@ void AActor::SetAngle(DAngle ang, int fflags)
 {
 	if (ang != Angles.Yaw)
 	{
-		Angles.Yaw = ang;
-		if (player != nullptr && (fflags & SPF_INTERPOLATE))
+		if (player != nullptr)
 		{
-			player->cheats |= CF_INTERPVIEW;
+			if (fflags & SPF_INTERPOLATE)
+			{
+				if (P_NoInterpolation(player, this))
+				{
+					player->angleTargets.Yaw = deltaangle(Angles.Yaw, ang);
+					player->angleAppliedAmounts.Yaw = nullAngle;
+				}
+				else
+				{
+					Angles.Yaw = ang;
+					player->cheats |= CF_INTERPVIEW;
+				}
+			}
+		}
+		else
+		{
+			Angles.Yaw = ang;
 		}
 	}
 	
@@ -3453,10 +3483,25 @@ void AActor::SetRoll(DAngle r, int fflags)
 {
 	if (r != Angles.Roll)
 	{
-		Angles.Roll = r;
-		if (player != nullptr && (fflags & SPF_INTERPOLATE))
+		if (player != nullptr)
 		{
-			player->cheats |= CF_INTERPVIEW;
+			if (fflags & SPF_INTERPOLATE)
+			{
+				if (P_NoInterpolation(player, this))
+				{
+					player->angleTargets.Roll = deltaangle(Angles.Roll, r);
+					player->angleAppliedAmounts.Roll = nullAngle;
+				}
+				else
+				{
+					Angles.Roll = r;
+					player->cheats |= CF_INTERPVIEW;
+				}
+			}
+		}
+		else
+		{
+			Angles.Roll = r;
 		}
 	}
 }
diff --git a/src/rendering/r_utility.cpp b/src/rendering/r_utility.cpp
index 80690db12..1af920a7f 100644
--- a/src/rendering/r_utility.cpp
+++ b/src/rendering/r_utility.cpp
@@ -762,6 +762,35 @@ static double QuakePower(double factor, double intensity, double offset)
 	return factor * (offset + randumb);
 }
 
+//==========================================================================
+//
+// R_DoActorTickerAngleChanges
+//
+//==========================================================================
+
+static void R_DoActorTickerAngleChanges(player_t* const player, AActor* const actor, const double scale)
+{
+	for (unsigned i = 0; i < 3; i++)
+	{
+		if (player->angleTargets[i].Sgn())
+		{
+			// Calculate scaled amount of target and add to the accumlation buffer.
+			DAngle addition = player->angleTargets[i] * scale;
+			player->angleAppliedAmounts[i] += addition;
+
+			// Test whether we're now reached/exceeded our target.
+			if (abs(player->angleAppliedAmounts[i]) >= abs(player->angleTargets[i]))
+			{
+				addition -= player->angleAppliedAmounts[i] - player->angleTargets[i];
+				player->angleTargets[i] = player->angleAppliedAmounts[i] = nullAngle;
+			}
+
+			// Apply the scaled addition to the angle.
+			actor->Angles[i] += addition;
+		}
+	}
+}
+
 //==========================================================================
 //
 // R_SetupFrame
@@ -799,6 +828,12 @@ void R_SetupFrame (FRenderViewpoint &viewpoint, FViewWindow &viewwindow, AActor
 		I_Error ("You lost your body. Bad dehacked work is likely to blame.");
 	}
 
+	// [MR] Process player angle changes if permitted to do so.
+	if (player && P_NoInterpolation(player, viewpoint.camera))
+	{
+		R_DoActorTickerAngleChanges(player, viewpoint.camera, I_GetInputFrac(false));
+	}
+
 	iview = FindPastViewer (viewpoint.camera);
 
 	int nowtic = I_GetTime ();