WinBoard (Alien Edition) and the large Shogi variants

Large Shogi variants feature a staggering number of piece types. Even Chu Shogi, played on a 12x12 board, has 21 different pieces (for each side!) in the initial setup, 18 of which promote to different types (so 39 types in total). This runs up to the many hundreds in Taikyoku Shogi. The standard version of WinBoards, although quite supportive of variants, 'only' implements 22 piece types.

There exists a fork of WinBoard, known as the Alien Edition, which incorporates a number of features that the standard version does not have. In particular the possibility to deligate highlighting of board squares where pieces can move to the engine, and the possibility to move multiple pieces per turn (or a single piece multiple times). As these features are also needed for the Lion piece occurring in the large Shogi variants, the Alien Edition has been chosen to be equiped with specific support for the large Shogi variants. Note that WinBoard is just an interface, or 'electronic Chess board', and cannot think up moves for the games it supports by itself. It needs an 'engine' for that task. For the large Shogi variants the engine HaChu is available.

A multitude of piece types

To support large Shogi variants, the maximum board size and the number of piece types in the Alien Edition has been hugely expanded. This required implementation of a new method for rendering the piece graphics. Having prepared bitmaps for all the required pieces seemed no longer feasible, even for a single board size (WinBoard supports 18 board sizes...) and in stead a list was added that contains a description of each piece type. This description consists of a code indicating how far it moves in each of the eight major directions, and the kanj to spell the piece name both in single-kanj and double-kanji notation. This list can then be used to construct a bitmap for the piece based on how it moves (the so-called mnemonic piece set), from a limited set of bitmaps for the various elements. For a limited number of pieces with irregular moves, dedicated bitmaps were added to represent them, and the general method is only used if no dedicated bitmap is available. The mnemonic piece set is available at board sizes tiny and petite (with squares of 21x21 and 33x33 pixels, respectively).

Highlighting target squares

When legality checking is on, WinBoard will use the move description in the piece tables to highlight the squares a piece can move to when you pick up that piece. It can get that information from the piece table, which is reasonably detailed. (It is, for instance, aware of the ability of the Tenjiku jumping generals to jump.) It is not aware of the very subtle details of the rules, however, such as the rules for Lions capturing each other in Chu Shogi. Therefore it is better to use WinBoard with legality checking off, which then makes the engine responsible for the highlighting and legality checking. (This obviously only holds if you do use WinBoard with an engine, and not in game-viewer mode.)

Multiple moving

Pieces like the Lion can do two steps per turn, capturing something on the 'intermediate square' before stepping on, very similar to e.p. capture. But unlike e.p. capture, the victim cannot be implied by the final square, as the latter can usually be reached through multiple paths, or jumped to directly. So both steps have to be indicated by the user to enter a complete Lion move. WinBoard's Alien Edition has a general method for entering such multi-leg moves, namely keeping Ctrl pressed while entering any legs that are not the last one.