Function LoadNextSprite

src/spritecache.cpp:614–681

* Load a real or recolour sprite. * @param load_index Global sprite index. * @param file GRF to load from. * @param file_sprite_id Sprite number in the GRF. * @param container_version Container version of the GRF. * @return True if a valid sprite was loaded, false on any error. */

 * @return True if a valid sprite was loaded, false on any error.
 */
bool LoadNextSprite(SpriteID load_index, SpriteFile &file, uint file_sprite_id)
{
	size_t file_pos = file.GetPos();

	/* Read sprite header. */
	uint32_t num = file.GetContainerVersion() >= 2 ? file.ReadDword() : file.ReadWord();
	if (num == 0) return false;
	uint8_t grf_type = file.ReadByte();

	SpriteType type;
	SpriteCacheCtrlFlags control_flags;
	if (grf_type == 0xFF) {
		/* Some NewGRF files have "empty" pseudo-sprites which are 1
		 * byte long. Catch these so the sprites won't be displayed. */
		if (num == 1) {
			file.ReadByte();
			return false;
		}
		file_pos = file.GetPos();
		type = SpriteType::Recolour;
		file.SkipBytes(num);
	} else if (file.GetContainerVersion() >= 2 && grf_type == 0xFD) {
		if (num != 4) {
			/* Invalid sprite section include, ignore. */
			file.SkipBytes(num);
			return false;
		}
		/* It is not an error if no sprite with the provided ID is found in the sprite section. */
		auto iter = _grf_sprite_offsets.find(file.ReadDword());
		if (iter != _grf_sprite_offsets.end()) {
			file_pos = iter->second.file_pos;
			control_flags = iter->second.control_flags;
		} else {
			file_pos = SIZE_MAX;
		}
		type = SpriteType::Normal;
	} else {
		file.SkipBytes(7);
		type = SkipSpriteData(file, grf_type, num - 8) ? SpriteType::Normal : SpriteType::Invalid;
		/* Inline sprites are not supported for container version >= 2. */
		if (file.GetContainerVersion() >= 2) return false;
	}

	if (type == SpriteType::Invalid) return false;

	if (load_index >= MAX_SPRITES) {
		UserError("Tried to load too many sprites (#{}; max {})", load_index, MAX_SPRITES);
	}

	bool is_mapgen = IsMapgenSpriteID(load_index);

	if (is_mapgen) {
		if (type != SpriteType::Normal) UserError("Uhm, would you be so kind not to load a NewGRF that changes the type of the map generator sprites?");
		type = SpriteType::MapGen;
	}

	SpriteCache *sc = AllocateSpriteCache(load_index);
	sc->file = &file;