Function CheckClickOnVehicle

src/vehicle.cpp:1215–1264

* Find the vehicle close to the clicked coordinates. * @param vp Viewport clicked in. * @param x X coordinate in the viewport. * @param y Y coordinate in the viewport. * @return Closest vehicle, or \c nullptr if none found. */

 * @return Closest vehicle, or \c nullptr if none found.
 */
Vehicle *CheckClickOnVehicle(const Viewport &vp, int x, int y)
{
	Vehicle *found = nullptr;
	uint dist, best_dist = UINT_MAX;

	x -= vp.left;
	y -= vp.top;
	if (!IsInsideMM(x, 0, vp.width) || !IsInsideMM(y, 0, vp.height)) return nullptr;

	x = ScaleByZoom(x, vp.zoom) + vp.virtual_left;
	y = ScaleByZoom(y, vp.zoom) + vp.virtual_top;

	/* Border size of MAX_VEHICLE_PIXEL_xy */
	const int xb = MAX_VEHICLE_PIXEL_X * ZOOM_BASE;
	const int yb = MAX_VEHICLE_PIXEL_Y * ZOOM_BASE;

	/* The hash area to scan */
	uint xl = GetViewportHashX(x - xb);
	uint xu = GetViewportHashX(x);
	uint yl = GetViewportHashY(y - yb);
	uint yu = GetViewportHashY(y);

	for (uint hy = yl;; hy = (hy + GEN_HASHY_INC) & GEN_HASHY_MASK) {
		for (uint hx = xl;; hx = (hx + GEN_HASHX_INC) & GEN_HASHX_MASK) {
			Vehicle *v = _vehicle_viewport_hash[hx + hy]; // already masked & 0xFFF

			while (v != nullptr) {
				if (!v->vehstatus.Any({VehState::Hidden, VehState::Unclickable}) &&
					x >= v->coord.left && x <= v->coord.right &&
					y >= v->coord.top && y <= v->coord.bottom) {

					dist = std::max(
						abs(((v->coord.left + v->coord.right) >> 1) - x),
						abs(((v->coord.top + v->coord.bottom) >> 1) - y)
					);

					if (dist < best_dist) {
						found = v;
						best_dist = dist;
					}
				}
				v = v->hash_viewport_next;
			}
			if (hx == xu) break;
		}
		if (hy == yu) break;
	}

	return found;
}

/**
 * Decrease the value of a vehicle.