Rumble the jart when stepping on staircases

- Sprite tilts back and forth 5.625 degrees, two tics each
  side, for 17 tics (half a second).
- Turning is ignored--as if in the air--every other tic
  during those 17 tics.

src/d_player.h

@@ -708,6 +708,8 @@ typedef struct player_s
 
 	UINT8 kickstartaccel;
 
+	UINT8 stairjank;
+
 #ifdef HWRENDER
 	fixed_t fovadd; // adjust FOV for hw rendering
 #endif

src/k_kart.c

@@ -1761,11 +1761,6 @@ static void K_SpawnBrakeDriftSparks(player_t *player) // Be sure to update the m
 	sparks->renderflags |= RF_DONTDRAW;
 }
 
-static fixed_t K_RandomFlip(fixed_t f)
-{
-	return ( ( leveltime & 1 ) ? f : -f );
-}
-
 void K_SpawnDriftBoostClip(player_t *player)
 {
 	mobj_t *clip;
@@ -1790,7 +1785,7 @@ void K_SpawnDriftBoostClip(player_t *player)
 		clip->momz += player->mo->momz;
 
 	P_InstaThrust(clip, player->mo->angle +
-			K_RandomFlip(P_RandomRange(FRACUNIT/2, FRACUNIT)),
+			P_RandomFlip(P_RandomRange(FRACUNIT/2, FRACUNIT)),
 			FixedMul(scale, player->speed));
 }
 

src/p_map.c

@@ -2419,6 +2419,8 @@ boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
 	fixed_t radius = thing->radius;
 	fixed_t thingtop;
 	fixed_t startingonground = P_IsObjectOnGround(thing);
+	fixed_t stairjank = 0;
+	fixed_t stairstep = 0;
 	floatok = false;
 
 	// reset this to 0 at the start of each trymove call as it's only used here
@@ -2490,6 +2492,8 @@ boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
 
 			if (maxstep > 0)
 			{
+				const fixed_t minstep = maxstep / 8;
+
 				thingtop = thing->z + thing->height;
 
 				// Step up
@@ -2497,6 +2501,9 @@ boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
 				{
 					if (tmfloorstep <= maxstep)
 					{
+						stairjank = thing->floordrop;
+						stairstep = minstep;
+
 						thing->z = thing->floorz = tmfloorz;
 						thing->floorrover = tmfloorrover;
 						thing->eflags |= MFE_JUSTSTEPPEDDOWN;
@@ -2510,6 +2517,9 @@ boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
 				{
 					if (tmceilingstep <= maxstep)
 					{
+						stairjank = thing->ceilingdrop;
+						stairstep = minstep;
+
 						thing->z = ( thing->ceilingz = tmceilingz ) - thing->height;
 						thing->ceilingrover = tmceilingrover;
 						thing->eflags |= MFE_JUSTSTEPPEDDOWN;
@@ -2526,6 +2536,9 @@ boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
 
 					if (thingtop == thing->ceilingz && tmceilingz > thingtop && tmceilingz - thingtop <= maxstep)
 					{
+						stairjank = thing->ceilingdrop;
+						stairstep = minstep;
+
 						thing->z = (thing->ceilingz = tmceilingz) - thing->height;
 						thing->ceilingrover = tmceilingrover;
 						thing->eflags |= MFE_JUSTSTEPPEDDOWN;
@@ -2533,6 +2546,9 @@ boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
 					}
 					else if (thing->z == thing->floorz && tmfloorz < thing->z && thing->z - tmfloorz <= maxstep)
 					{
+						stairjank = thing->floordrop;
+						stairstep = minstep;
+
 						thing->z = thing->floorz = tmfloorz;
 						thing->floorrover = tmfloorrover;
 						thing->eflags |= MFE_JUSTSTEPPEDDOWN;
@@ -2619,6 +2635,11 @@ boolean P_TryMove(mobj_t *thing, fixed_t x, fixed_t y, boolean allowdropoff)
 	else // don't set standingslope if you're not going to clip against it
 		thing->standingslope = NULL;
 
+	if (stairjank > stairstep && thing->player)
+	{
+		thing->player->stairjank = 17;
+	}
+
 	thing->x = x;
 	thing->y = y;
 

src/p_tick.c

@@ -36,6 +36,11 @@
 
 tic_t leveltime;
 
+INT32 P_AltFlip(INT32 n, tic_t tics)
+{
+	return leveltime % (2 * tics) < tics ? n : -(n);
+}
+
 //
 // THINKERS
 // All thinkers should be allocated by Z_Calloc

src/p_tick.h

@@ -30,4 +30,8 @@ void P_DoTeamscrambling(void);
 void P_RemoveThinkerDelayed(thinker_t *thinker); //killed
 mobj_t *P_SetTarget(mobj_t **mo, mobj_t *target);   // killough 11/98
 
+// Negate the value for tics
+INT32 P_AltFlip(INT32 value, tic_t tics);
+#define P_RandomFlip(value) P_AltFlip(value, 1)
+
 #endif

src/p_user.c

@@ -1869,6 +1869,9 @@ static void P_3dMovement(player_t *player)
 		movepushangle = player->mo->angle-(ANGLE_45/5)*player->kartstuff[k_drift];
 	else if (player->kartstuff[k_spinouttimer] || player->kartstuff[k_wipeoutslow])	// if spun out, use the boost angle
 		movepushangle = (angle_t)player->kartstuff[k_boostangle];
+	else if (player->stairjank && leveltime & 1)
+		movepushangle = R_PointToAngle2(0, 0,
+				player->mo->momx, player->mo->momy);
 	else
 		movepushangle = player->mo->angle;
 
@@ -4749,6 +4752,11 @@ void P_PlayerThink(player_t *player)
 		player->typing_duration = 0;
 	}
 
+	if (player->stairjank > 0)
+	{
+		player->stairjank--;
+	}
+
 	player->pflags &= ~PF_SLIDING;
 
 	K_KartPlayerThink(player, cmd); // SRB2kart

src/r_patchrotation.c

@@ -15,6 +15,7 @@
 #include "w_wad.h"
 #include "r_main.h" // R_PointToAngle
 #include "k_kart.h" // K_Sliptiding
+#include "p_tick.h"
 
 #ifdef ROTSPRITE
 fixed_t rollcosang[ROTANGLES];
@@ -32,16 +33,14 @@ angle_t R_GetPitchRollAngle(mobj_t *mobj)
 	return rollOrPitch;
 }
 
-angle_t R_SpriteRotationAngle(mobj_t *mobj)
+static angle_t R_PlayerSpriteRotation(player_t *player)
 {
-	angle_t viewingAngle = R_PointToAngle(mobj->x, mobj->y);
-	angle_t angleDelta = (viewingAngle - mobj->angle);
+	angle_t viewingAngle = R_PointToAngle(player->mo->x, player->mo->y);
+	angle_t angleDelta = (viewingAngle - player->mo->angle);
 
-	angle_t sliptideLift = mobj->player
-		? mobj->player->aizDriftTilt : 0;
+	angle_t sliptideLift = player->aizDriftTilt;
 
-	angle_t rollOrPitch = R_GetPitchRollAngle(mobj);
-	angle_t rollAngle = (rollOrPitch + mobj->rollangle);
+	angle_t rollAngle = 0;
 
 	if (sliptideLift)
 	{
@@ -52,6 +51,25 @@ angle_t R_SpriteRotationAngle(mobj_t *mobj)
 			FixedMul(sliptideLift, FINECOSINE(angleDelta >> ANGLETOFINESHIFT));
 	}
 
+	if (player->stairjank)
+	{
+		rollAngle += P_AltFlip(ANGLE_11hh / 2 /
+				(17 / player->stairjank), 2);
+	}
+
+	return rollAngle;
+}
+
+angle_t R_SpriteRotationAngle(mobj_t *mobj)
+{
+	angle_t rollOrPitch = R_GetPitchRollAngle(mobj);
+	angle_t rollAngle = (rollOrPitch + mobj->rollangle);
+
+	if (mobj->player)
+	{
+		rollAngle += R_PlayerSpriteRotation(mobj->player);
+	}
+
 	return rollAngle;
 }