Restore Boom friction code for demo compatibility (#127)

* Restore Boom friction code for demo compatibility

* clean up

* fix original indentation

* try to fix indent again

* more indent fixes

Source/p_map.c

@@ -170,6 +170,49 @@ int P_GetMoveFactor(const mobj_t *mo, int *frictionp)
 {
   int movefactor, friction;
 
+  // Restore original Boom friction code for
+  // demo compatibility
+  if (demo_version < 203)
+  {
+    int momentum;
+
+    movefactor = ORIG_FRICTION_FACTOR;
+
+    if (!compatibility && variable_friction &&
+      !(mo->flags & (MF_NOGRAVITY | MF_NOCLIP)))
+    {
+      friction = mo->friction;
+      if (friction == ORIG_FRICTION)            // normal floor
+        ;
+      else if (friction > ORIG_FRICTION)        // ice
+      {
+        movefactor = mo->movefactor;
+        ((mobj_t*)mo)->movefactor = ORIG_FRICTION_FACTOR;  // reset
+      }
+      else                                      // sludge
+      {
+
+        // phares 3/11/98: you start off slowly, then increase as
+        // you get better footing
+
+        momentum = (P_AproxDistance(mo->momx,mo->momy));
+        movefactor = mo->movefactor;
+        if (momentum > MORE_FRICTION_MOMENTUM<<2)
+          movefactor <<= 3;
+
+        else if (momentum > MORE_FRICTION_MOMENTUM<<1)
+          movefactor <<= 2;
+
+        else if (momentum > MORE_FRICTION_MOMENTUM)
+          movefactor <<= 1;
+
+        ((mobj_t*)mo)->movefactor = ORIG_FRICTION_FACTOR;  // reset
+      }
+    }                                                       //     ^
+
+    return(movefactor);                                       //     |
+  }
+
   // If the floor is icy or muddy, it's harder to get moving. This is where
   // the different friction factors are applied to 'trying to move'. In
   // p_mobj.c, the friction factors are applied as you coast and slow down.
@@ -1021,12 +1064,24 @@ static void P_HitSlideLine(line_t *ld)
   // Check for the special cases of horz or vert walls.
 
   // killough 10/98: only bounce if hit hard (prevents wobbling)
+
+  if (demo_version >= 203)
+  {
   icyfloor = 
-    (demo_version >= 203 ? 
+     P_AproxDistance(tmxmove, tmymove) > 4*FRACUNIT &&
-     P_AproxDistance(tmxmove, tmymove) > 4*FRACUNIT : !compatibility) &&
     variable_friction &&  // killough 8/28/98: calc friction on demand
     slidemo->z <= slidemo->floorz &&
     P_GetFriction(slidemo, NULL) > ORIG_FRICTION;
+  }
+  else
+  {
+    extern boolean onground;
+    icyfloor = !compatibility &&
+    variable_friction &&
+    slidemo->player &&
+    onground && 
+    slidemo->friction > ORIG_FRICTION;
+  }
 
   if (ld->slopetype == ST_HORIZONTAL)
     {

Source/p_mobj.c

@@ -134,6 +134,8 @@ void P_XYMovement (mobj_t* mo)
   player_t *player;
   fixed_t xmove, ymove;
 
+  fixed_t oldx,oldy; // phares 9/10/98: reducing bobbing/momentum on ice
+
   if (!(mo->momx | mo->momy)) // Any momentum?
     {
       if (mo->flags & MF_SKULLFLY)
@@ -165,6 +167,10 @@ void P_XYMovement (mobj_t* mo)
   xmove = mo->momx;
   ymove = mo->momy;
 
+  oldx = mo->x; // phares 9/10/98: new code to reduce bobbing/momentum
+  oldy = mo->y; // when on ice & up against wall. These will be compared
+                // to your x,y values later to see if you were able to move
+
   do
     {
       fixed_t ptryx, ptryy;
@@ -326,6 +332,26 @@ void P_XYMovement (mobj_t* mo)
       // Reducing player momentum is no longer needed to reduce
       // bobbing, so ice works much better now.
 
+      if (demo_version < 203)
+      {
+        // phares 9/10/98: reduce bobbing/momentum when on ice & up against wall
+
+        if ((oldx == mo->x) && (oldy == mo->y)) // Did you go anywhere?
+          { // No. Use original friction. This allows you to not bob so much
+            // if you're on ice, but keeps enough momentum around to break free
+            // when you're mildly stuck in a wall.
+          mo->momx = FixedMul(mo->momx,ORIG_FRICTION);
+          mo->momy = FixedMul(mo->momy,ORIG_FRICTION);
+          }
+        else
+          { // Yes. Use stored friction.
+          mo->momx = FixedMul(mo->momx,mo->friction);
+          mo->momy = FixedMul(mo->momy,mo->friction);
+          }
+        mo->friction = ORIG_FRICTION; // reset to normal for next tic
+      }
+      else
+      {
       fixed_t friction = P_GetFriction(mo, NULL);
 
       mo->momx = FixedMul(mo->momx, friction);
@@ -340,6 +366,7 @@ void P_XYMovement (mobj_t* mo)
 	  player->momx = FixedMul(player->momx, ORIG_FRICTION);
 	  player->momy = FixedMul(player->momy, ORIG_FRICTION);
 	}
+     }
     }
 }
 
@@ -769,6 +796,9 @@ mobj_t *P_SpawnMobj(fixed_t x, fixed_t y, fixed_t z, mobjtype_t type)
   mobj->thinker.function = P_MobjThinker;
   mobj->above_thing = mobj->below_thing = 0;           // phares
 
+  // for Boom friction code
+  mobj->friction    = ORIG_FRICTION;                        // phares 3/17/98
+
   P_AddThinker(&mobj->thinker);
 
   return mobj;

Source/p_mobj.h

@@ -336,6 +336,10 @@ typedef struct mobj_s
 
     // killough 8/2/98: friction properties part of sectors,
     // not objects -- removed friction properties from here
+    // e6y: restored friction properties here
+    // Friction values for the sector the object is in
+    int friction;                                           // phares 3/17/98
+    int movefactor;
 
     // a linked list of sectors where this object appears
     struct msecnode_s* touching_sectorlist;                 // phares 3/14/98

Source/p_spec.c

@@ -2691,6 +2691,79 @@ static void P_SpawnScrollers(void)
     }
 }
 
+// Restored Boom's friction code
+
+/////////////////////////////
+//
+// Add a friction thinker to the thinker list
+//
+// Add_Friction adds a new friction thinker to the list of active thinkers.
+//
+
+static void Add_Friction(int friction, int movefactor, int affectee)
+{
+    friction_t *f = Z_Malloc(sizeof *f, PU_LEVSPEC, 0);
+
+    f->thinker.function/*.acp1*/ = /*(actionf_p1) */T_Friction;
+    f->friction = friction;
+    f->movefactor = movefactor;
+    f->affectee = affectee;
+    P_AddThinker(&f->thinker);
+}
+
+/////////////////////////////
+//
+// This is where abnormal friction is applied to objects in the sectors.
+// A friction thinker has been spawned for each sector where less or
+// more friction should be applied. The amount applied is proportional to
+// the length of the controlling linedef.
+
+void T_Friction(friction_t *f)
+{
+    sector_t *sec;
+    mobj_t   *thing;
+    msecnode_t* node;
+
+    if (compatibility || !variable_friction)
+        return;
+
+    sec = sectors + f->affectee;
+
+    // Be sure the special sector type is still turned on. If so, proceed.
+    // Else, bail out; the sector type has been changed on us.
+
+    if (!(sec->special & FRICTION_MASK))
+        return;
+
+    // Assign the friction value to players on the floor, non-floating,
+    // and clipped. Normally the object's friction value is kept at
+    // ORIG_FRICTION and this thinker changes it for icy or muddy floors.
+
+    // In Phase II, you can apply friction to Things other than players.
+
+    // When the object is straddling sectors with the same
+    // floorheight that have different frictions, use the lowest
+    // friction value (muddy has precedence over icy).
+
+    node = sec->touching_thinglist; // things touching this sector
+    while (node)
+    {
+        thing = node->m_thing;
+        if (thing->player &&
+            !(thing->flags & (MF_NOGRAVITY | MF_NOCLIP)) &&
+            thing->z <= sec->floorheight)
+            {
+                if ((thing->friction == ORIG_FRICTION) ||     // normal friction?
+                    (f->friction < thing->friction))
+                    {
+                      thing->friction   = f->friction;
+                      thing->movefactor = f->movefactor;
+                    }
+            }
+        node = node->m_snext;
+    }
+}
+
 // killough 3/7/98 -- end generalized scroll effects
 
 ////////////////////////////////////////////////////////////////////////////
@@ -2792,6 +2865,10 @@ static void P_SpawnFriction(void)
             // drag on CPU. New code adjusts friction of sector only once
             // at level startup, and then uses this friction value.
 
+            // Boom's friction code for demo compatibility
+            if (!demo_compatibility && demo_version < 203)
+              Add_Friction(friction,movefactor,s);
+
             sectors[s].friction = friction;
             sectors[s].movefactor = movefactor;
           }

Source/p_user.c

@@ -73,6 +73,9 @@ void P_Thrust(player_t* player,angle_t angle,fixed_t move)
 
 void P_Bob(player_t *player, angle_t angle, fixed_t move)
 {
+  if (demo_version < 203)
+    return;
+
   player->momx += FixedMul(move,finecosine[angle >>= ANGLETOFINESHIFT]);
   player->momy += FixedMul(move,finesine[angle]);
 }
@@ -102,14 +105,24 @@ void P_CalcHeight (player_t* player)
 
   // [FG] MBF player bobbing rewrite causes demo sync problems
   // http://prboom.sourceforge.net/mbf-bugs.html
-  player->bob = demo_compatibility ?
+  player->bob = (demo_compatibility || player_bobbing) ?
     (FixedMul (player->mo->momx, player->mo->momx)
      + FixedMul (player->mo->momy,player->mo->momy))>>2 :
-    player_bobbing ? (FixedMul(player->momx,player->momx) +
+    (demo_version >= 203 && player_bobbing) ? (FixedMul(player->momx,player->momx) +
         FixedMul(player->momy,player->momy))>>2 : 0;
 
-  if (player->bob > MAXBOB)                             
+  if ((demo_version == 202 || 
+      demo_version == 203) &&
+      player->mo->friction > ORIG_FRICTION) // ice?
+  {
+    if (player->bob > (MAXBOB>>2))
+      player->bob = MAXBOB>>2;
+  }
+  else
+  {
+  if (player->bob > MAXBOB)
     player->bob = MAXBOB;
+  }
 
   if (!onground || player->cheats & CF_NOMOMENTUM)
     {
@@ -186,7 +199,7 @@ void P_MovePlayer (player_t* player)
   // ice, because the player still "works just as hard" to move, while the
   // thrust applied to the movement varies with 'movefactor'.
 
-  if (cmd->forwardmove | cmd->sidemove) // killough 10/98
+  if ((!demo_compatibility && demo_version < 203) || cmd->forwardmove | cmd->sidemove) // killough 10/98
     {
       if (onground || mo->flags & MF_BOUNCES) // killough 8/9/98
 	{