section of the player collision detection thing as of 2024-05-24

bool Player::colliding(shape::rect thing_rect, shape::fpoint* target_p){
  //convert the 2 rects from x,y,w,h to x0,y0,x1,y1
  thing_rect.w += thing_rect.x; //convert width and height to a second point
  thing_rect.h += thing_rect.y;  //that defines the thing's bounding box

   //(size of the bounding box, anyway)
  shape::point player_size(RND(6.0f*scale), RND(8.0f*scale));

  shape::rect player_rect;
  player_rect.x = RND(pos.x)    - player_size.x/2;
  player_rect.y = RND(pos.y)    - player_size.y/2;
  player_rect.w = player_rect.x + player_size.x  ;
  player_rect.h = player_rect.y + player_size.y  ;



  //detect collision while getting the area of intersection
  shape::rect inter_rect; //inter[section]
  inter_rect.x = MAX(player_rect.x, thing_rect.x); //max of left edges
  inter_rect.y = MAX(player_rect.y, thing_rect.y); //max of top edges
  inter_rect.w = MIN(player_rect.w, thing_rect.w); //min of right edges
  inter_rect.h = MIN(player_rect.h, thing_rect.h); //min of bottom edges

  bool collision = inter_rect.x < inter_rect.w  &&  inter_rect.y < inter_rect.h;

  //forward declare some stuff so msvc doesn't complain about me using gotos
  shape::fpoint thing_center;
  shape::fpoint target; //'where should the player have to move to avoid thing?'
  bool horizontal; //'should player be displaced vertically or horizontally?'
  if(!collision) goto _draw_collisions_;



  thing_center.x = (f32)(thing_rect.x + thing_rect.w)/2;
  thing_center.y = (f32)(thing_rect.y + thing_rect.h)/2;

#if defined(_DEBUG) && defined(SHOW_COLLISIONS)
  if(thing_center.x > pos.x) inter_rect.w  = -(inter_rect.w - inter_rect.x);
  else                       inter_rect.w -= inter_rect.x;
  if(thing_center.y > pos.y) inter_rect.h  = -(inter_rect.h - inter_rect.y);
  else                       inter_rect.h -= inter_rect.y;
#endif /* if defined(_DEBUG) && defined(SHOW_COLLISIONS) */



  thing_center -= pos; //get position of thing relative to the player

  //'should player be displaced vertically or horizontally?'
  horizontal = fabsf(thing_center.x) >= fabsf(thing_center.y);

  //to prevent the player from potentially getting stuck due to rounding errors
  #define EPSILON 0.0001f

  if(horizontal){
    if(thing_center.x>0) target.x = thing_rect.x-(3.0f*scale)-EPSILON; //push left
    else                 target.x = thing_rect.w+(3.0f*scale)+EPSILON; //push right

  } else { //vertical
    if(thing_center.y>0) target.y = thing_rect.y-(4.0f*scale)-EPSILON; //push up
    else                 target.y = thing_rect.h+(4.0f*scale)+EPSILON; //push down

  }

  if(target_p) *target_p = target;

  //_printf("%5.2f, %5.2f\n", delta.x, delta.y);
  _printf("%3i, %3i, %3i, %3i\n", thing_rect.x, thing_rect.y, thing_rect.w, thing_rect.h);



  _draw_collisions_:
#if defined(_DEBUG) && defined(SHOW_COLLISIONS)

  //(make sure inter_rect's width and height is positive)
  if(inter_rect.w < 0) inter_rect.w = -inter_rect.w;
  if(inter_rect.h < 0) inter_rect.h = -inter_rect.h;
  if(collision) gl_win->drawRectangles(&inter_rect, 1, 0x007fff);


  shape::point p[5];
  shape::point thing_center_s32;
  thing_center_s32.x = (thing_rect.x + thing_rect.w)/2;
  thing_center_s32.y = (thing_rect.y + thing_rect.h)/2;

  if(collision){
    p[0] = shape::point(thing_center_s32.x, thing_center_s32.y);
    p[1] = shape::point(thing_rect.x  , thing_rect.y  );
    p[2] = shape::point(thing_rect.w-1, thing_rect.y  );
    p[3] = shape::point(thing_rect.x,   thing_rect.h-1);
    p[4] = shape::point(thing_rect.w-1, thing_rect.h-1);
    gl_win->drawLines((shape::point*)&p, 2, 0xffffff); p[1] = p[2];
    gl_win->drawLines((shape::point*)&p, 2, 0xffffff); p[1] = p[3];
    gl_win->drawLines((shape::point*)&p, 2, 0xffffff); p[1] = p[4];
    gl_win->drawLines((shape::point*)&p, 2, 0xffffff);
  }


  p[0] = shape::point(thing_rect.x  , thing_rect.y  );
  p[1] = shape::point(thing_rect.w-1, thing_rect.y  );
  p[3] = shape::point(thing_rect.x,   thing_rect.h-1);
  p[2] = shape::point(thing_rect.w-1, thing_rect.h-1);
  p[4] = p[0];
  //gl_win->drawPoints((shape::point*)&p, lengthof(p,shape::point),
  //                   (collision) ? 0xff00 : 0xff0000, true);
  gl_win->drawLines((shape::point*)&p, lengthof(p,shape::point),
                    (collision) ? 0xff00 : 0xff0000, 1);


  p[0] = shape::point(player_rect.x  , player_rect.y  );
  p[1] = shape::point(player_rect.w-1, player_rect.y  );
  p[3] = shape::point(player_rect.x  , player_rect.h-1);
  p[2] = shape::point(player_rect.w-1, player_rect.h-1);
  p[4] = p[0];
  //gl_win->drawPoints((shape::point*)&p, lengthof(p,shape::point),
  //                   (collision) ? 0xff00 : 0xff0000, true);
  gl_win->drawLines((shape::point*)&p, lengthof(p,shape::point),
                    (collision) ? 0xff00 : 0xff0000, 1);


  if(collision){
    p[0] = shape::point(thing_center_s32.x, thing_center_s32.y);
    p[1] = shape::point((s32)pos.x, (s32)pos.y);
    gl_win->drawLines((shape::point*)&p, 2, (horizontal) ? 0x00ffff : 0xffff00);
    gl_textf((s32)gl_player.pos.x + PLAYER_HALF,
             (s32)gl_player.pos.y - PLAYER_HALF,
             "horizontal=%s", boolStr(horizontal));
  }

#endif /* if defined(_DEBUG) && defined(SHOW_COLLISIONS) */


  return collision;

}