new work inside globals.cpp

//returns true only if resulting bounds have volume
static inline bool get_tile_bounds(shape_quad& bounds){
  //find the boundaries of all tiles that the player is touching
   //(+= 11 so that an east/south subtile boundary is crossed only when
   // a pixel of the player sprite actually overlaps a given tile)
  bounds.b += shape::point(11, 11);
  bounds /= 12; //convert pixels to subtiles
   //
  bounds.a.x = CLAMP(bounds.a.x, 0, TILESIZ_X*2); //skip subtiles that are off-screen
  bounds.a.y = CLAMP(bounds.a.y, 0, TILESIZ_Y*2);  //(2 subtiles in a tile lengthwise)
   //
  bounds.b.x = CLAMP(bounds.b.x, 0, TILESIZ_X*2);
  bounds.b.y = CLAMP(bounds.b.y, 0, TILESIZ_Y*2);

  s32 xmin, xmax,  ymin, ymax;

  if(abs(bounds.a.x)<abs(bounds.b.x)){ xmin = abs(bounds.a.x),  xmax = abs(bounds.b.x); }
  else                               { xmin = abs(bounds.b.x),  xmax = abs(bounds.a.x); }

  if(abs(bounds.a.y)<abs(bounds.b.y)){ ymin = abs(bounds.a.y),  ymax = abs(bounds.b.y); }
  else                               { ymin = abs(bounds.b.y),  ymax = abs(bounds.a.y); }

  return (xmax-xmin)>0 && (ymax-ymin)>0;

}



#define SO_LOOP_PATTERN 0
bool subtiles_overlapping(shape::rect& object_rect_ref, shape::point* delta_p){
  shape::rect object_rect = object_rect_ref;
  shape_quad  bounds      = object_rect;

  shape::point delta(0, 0); //neutral delta by default

  if(!get_tile_bounds(bounds)){ //there are no subtiles to check; exit early
    if(delta_p) *delta_p = delta;
    return false;
  }

  shape::point min = bounds.a;
  shape::point max = bounds.b;
  shape::point sub;             //current subtile position
  shape::rect  col(0,0, 12,12); //subtile collider

#if SO_LOOP_PATTERN == 1
  s32 xmid = (min.x+max.x)/2; //x midpoint
  /* bottom-to-top vertically (y = max.y-1;  y >= min.y;  --y)
       right-to-left on the left half  (x = xmid-1;  x >= min.x;  --x)
       left-to-right on the right half (x = xmid  ;  x <  max.x;  ++x) */
  //(tbd)

#else
  for(sub.y = max.y-1;  sub.y >= min.y;  --sub.y) //bottom-to-top vertically
  for(sub.x = min.x  ;  sub.x <  max.x;  ++sub.x) //left-to-right horizontally
    if(subtile_is_collidable(sub.x, sub.y)){
      col.x = sub.x*12;
      col.y = sub.y*12;
      if(rects_overlapping(object_rect, col, &delta))
        object_rect += delta;

    }

#endif


  delta.x = object_rect.x - object_rect_ref.x;
  delta.y = object_rect.y - object_rect_ref.y;

  if(delta_p) *delta_p = delta;

  return delta.x!=0 || delta.y!=0;

}