Itxkeys: A robust key parser for LATEX

Currently, the three most popular software modules for creating and managing keys in (LA)TEX are the keyval, xkeyval and pgfkeys packages. The pgfkeys package is a part of the “portable graphics format” bundle of packages. This study concerns primarily the extensions of keyval and xkeyval packages by the ltxkeys package and not pgfkeys package, although ltxkeys provides tools that are not available in pgfkeys. The keyval and xkeyval packages are known to lack the level of robustness required for some modern applications of the machinery of keys in (LA)TEX. Specifically, they strip off outer curly braces in values of keys and are unable to parse key values that contain unbalanced conditionals. For large scale projects, the “selective sanitization” used by xkeyval package does slow down key processing. The keyval package can define only one type of key, while the xkeyval package can define up to four types of key. Four might sound many for key management, but the types of key that xkeyval package can handle are not sufficient to meet modern needs. Moreover, when it comes to defining several keys (of the same or different types), these packages require a relatively large estate to achieve this task. The ltxkeys package substantially extends the robustness and functionality of the keyval and xkeyval packages. Robustness results from the ability of the ltxkeys package to preserve outer braces in key values throughout parsing, as well as parse key values with unbalanced conditionals. The ltxkeys package can compactly define up to seven types of key, and, unlike in the keyval and xkeyval packages, it does provide for the definition of keys whose callback macros expect multi-parametered and delimited arguments. The ltxkeys package also introduces and robustly implements the concepts of key commands, key environments, pathkeys, amongst other new ideas in key management in (LA)TEX.