Method PixelToTile

src/smallmap_gui.cpp:1148–1169

* Determine the tile relative to the base tile of the smallmap, and the pixel position at * that tile for a point in the smallmap. * @param px Horizontal coordinate of the pixel. * @param py Vertical coordinate of the pixel. * @param[out] sub Pixel position at the tile (0..3). * @param add_sub Add current #subscroll to the position. * @return Tile being displayed at the gi

	 * @note The #subscroll offset is already accounted for.
	 */
	Point PixelToTile(int px, int py, int *sub, bool add_sub = true) const
	{
		if (add_sub) px += this->subscroll;  // Total horizontal offset.

		/* For each two rows down, add a x and a y tile, and
		 * For each four pixels to the right, move a tile to the right. */
		Point pt = {((py >> 1) - (px >> 2)) * this->zoom, ((py >> 1) + (px >> 2)) * this->zoom};
		px &= 3;

		if (py & 1) { // Odd number of rows, handle the 2 pixel shift.
			if (px < 2) {
				pt.x += this->zoom;
				px += 2;
			} else {
				pt.y += this->zoom;
				px -= 2;
			}
		}

		*sub = px;
		return pt;
	}

	/**
	 * Compute base parameters of the smallmap such that tile (\a tx, \a ty) starts at pixel (\a x, \a y).