From cda0441abb315cc57b479a98a96a4222aa2ea2e1 Mon Sep 17 00:00:00 2001
From: Sally Coolatta <tehrealsalt@gmail.com>
Date: Mon, 23 May 2022 00:36:03 -0400
Subject: [PATCH] Follower angle lag + lookback

- ANGLELAG lets you set how fast the followers swivel around. Default is 8*FRACUNIT, old behavior can be returned with FRACUNIT.
- Followers reverse their angle when you hold the lookback button.
- All lag values can't go below FRACUNIT instead of 1.
---
 src/deh_soc.c    | 10 ++++++++--
 src/k_follower.c | 24 +++++++++++++++++++++++-
 src/k_follower.h |  2 ++
 3 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/src/deh_soc.c b/src/deh_soc.c
index 6fe6ca36b..ba2845901 100644
--- a/src/deh_soc.c
+++ b/src/deh_soc.c
@@ -3827,6 +3827,7 @@ void readfollower(MYFILE *f)
 	followers[numfollowers].zoffs = 32*FRACUNIT;
 	followers[numfollowers].horzlag = 2*FRACUNIT;
 	followers[numfollowers].vertlag = 6*FRACUNIT;
+	followers[numfollowers].anglelag = 8*FRACUNIT;
 	followers[numfollowers].bobspeed = TICRATE*2;
 	followers[numfollowers].bobamp = 4*FRACUNIT;
 	followers[numfollowers].hitconfirmtime = TICRATE;
@@ -3888,6 +3889,10 @@ void readfollower(MYFILE *f)
 			{
 				followers[numfollowers].vertlag = (fixed_t)get_number(word2);
 			}
+			else if (fastcmp(word, "ANGLELAG"))
+			{
+				followers[numfollowers].vertlag = (fixed_t)get_number(word2);
+			}
 			else if (fastcmp(word, "BOBSPEED"))
 			{
 				followers[numfollowers].bobspeed = (tic_t)get_number(word2);
@@ -4002,8 +4007,9 @@ if ((signed)followers[numfollowers].field < threshold) \
 	FALLBACK(dist, "DIST", 0, 0);
 	FALLBACK(height, "HEIGHT", 1, 1);
 	FALLBACK(zoffs, "ZOFFS", 0, 0);
-	FALLBACK(horzlag, "HORZLAG", 1, 1);
-	FALLBACK(vertlag, "VERTLAG", 1, 1);
+	FALLBACK(horzlag, "HORZLAG", FRACUNIT, FRACUNIT);
+	FALLBACK(vertlag, "VERTLAG", FRACUNIT, FRACUNIT);
+	FALLBACK(anglelag, "ANGLELAG", FRACUNIT, FRACUNIT);
 	FALLBACK(bobamp, "BOBAMP", 0, 0);
 	FALLBACK(bobspeed, "BOBSPEED", 0, 0);
 	FALLBACK(hitconfirmtime, "HITCONFIRMTIME", 1, 1);
diff --git a/src/k_follower.c b/src/k_follower.c
index 42b956e9a..6973e0fcd 100644
--- a/src/k_follower.c
+++ b/src/k_follower.c
@@ -191,6 +191,8 @@ void K_HandleFollower(player_t *player)
 	fixed_t bubble; // bubble scale (0 if no bubble)
 	mobj_t *bmobj; // temp bubble mobj
 
+	angle_t destAngle, angleDiff;
+
 	if (player->followerready == false)
 	{
 		// we aren't ready to perform anything follower related yet.
@@ -346,7 +348,27 @@ void K_HandleFollower(player_t *player)
 		}
 
 		// if we're moving let's make the angle the direction we're moving towards. This is to avoid drifting / reverse looking awkward.
-		player->follower->angle = K_MomentumAngle(player->follower);
+		destAngle = K_MomentumAngle(player->follower);
+
+		// Sal: Turn the follower around when looking backwards.
+		if ( player->cmd.buttons & BT_LOOKBACK )
+		{
+			destAngle += ANGLE_180;
+		}
+
+		// Sal: Smoothly rotate angle to the destination value.
+		angleDiff = destAngle - player->follower->angle;
+
+		if (angleDiff > ANGLE_180)
+		{
+			angleDiff = InvAngle(FixedDiv(InvAngle(angleDiff), fl.anglelag));
+		}
+		else
+		{
+			angleDiff = FixedDiv(angleDiff, fl.anglelag);
+		}
+
+		player->follower->angle += angleDiff;
 
 		// Finally, if the follower has bubbles, move them, set their scale, etc....
 		// This is what I meant earlier by it being easier, now we can just use this weird lil loop to get the job done!
diff --git a/src/k_follower.h b/src/k_follower.h
index 807d9ac57..b5c740a22 100644
--- a/src/k_follower.h
+++ b/src/k_follower.h
@@ -45,6 +45,8 @@ typedef struct follower_s
 
 	fixed_t horzlag;		// Lag for X/Y displacement. Default is 2. Must be > 0 because we divide by this number.
 	fixed_t vertlag;		// Z displacement lag. Default is 6. Must be > 0 because we divide by this number.
+	fixed_t anglelag;		// Angle rotation lag. Default is 8. Must be > 0 because we divide by this number.
+
 	fixed_t bobamp;			// Bob amplitude. Default is 4.
 	tic_t bobspeed;			// Arbitrary modifier for bobbing speed. Default is TICRATE*2 (70)