Coroutine refactoring

Refactoring animation code using coroutines

Original inspiration (verbatim code):

void combatManager::ArcShot(icon *icn, int fromX, int fromY, int targX, int targY)
{
  bool firingLeft = false;
  if (fromX > targX)
    firingLeft = true;
  int imageIdx = 0; // changes the sprite when its angle changes

  // temporarily save the screen so we can clear it from the projectile sprite later
  // #3
  bitmap *savedscreen = new bitmap(0, INTERNAL_WINDOW_WIDTH, INTERNAL_WINDOW_HEIGHT);
  gpWindowManager->screenBuffer->CopyTo(savedscreen, 0, 0, 0, 0, INTERNAL_WINDOW_WIDTH, INTERNAL_WINDOW_HEIGHT);

  std::vector<COORD> points;
  // compute next point
  const int NUM_FRAMES = 24; // equals to the number of frames for the whole arc path
  while (next point is not null {
    if (i % 3 == 0) // every 3rd cycle
      if(imageIdx < (icn->numSprites - 1))
        imageIdx++; // changes the sprite of projectile
    // #3
    savedscreen->CopyTo(gpWindowManager->screenBuffer, 0, 0, 0, 0, INTERNAL_WINDOW_WIDTH, INTERNAL_WINDOW_HEIGHT); // clear the screen from the previous projectile sprite
    icn->CombatClipDrawToBuffer(points[i].X, points[i].Y, imageIdx, NULL, firingLeft, 0, 0, 0);
    gpWindowManager->UpdateScreenRegion(0, 0, INTERNAL_WINDOW_WIDTH, INTERNAL_WINDOW_HEIGHT);
    // gfCombatSpeedMod is 1 or .5ish
    glTimers = (signed __int64)((double)KBTickCount() + (double)40 * gfCombatSpeedMod[giCombatSpeed]); // #2
    DelayTil(&glTimers); // #2 .. blocking timer
    // compute next point
  }
  delete savedscreen;
  this->DrawFrame(1, 0, 0, 0, 1, 1, 1); // clear screen from the projectile
}


Refactored Python pseudocode:


def get_coord(...):
  for ...:
    velY -= gravity
    x += velX
    y += velY
    yield (x, y)
    doOtherThing()
    
  

def draw_projectile(...):
	color = true # that's why it's useful to use generators here
  for fr in projectile.frames:
  	color = !color
    draw(fr, point, color)
    next_point = yield # yield nothing!
  
coords = get_coord()
drawings = draw_projectile()
timing = get_timing()
for coord in coords:
  drawings.next(coord)
  timing.next()