Posting Diagrams and PGNs

[Harvey Williamson]

A huge thanks to HGM for all his hard work on these excellent board enhancements!

The forum now has three enhancements for chess, which can be invoked by enclosing the appropriate text within 'BBcode tags' (i.e., a tag name enclosed in square brackets):

'fen' tags — When these are put around a FEN position description, a diagram for that position will appear in your posting. The diagram generator is not pedantic about the format of the FEN; it ignores the castling rights and later parts, which can thus be omitted, and even omission of the side to move is not fatal. You can have as many ranks as you want, as long as there are at least 2, and ranks can contain as many squares as you want. (Doesn't even have to be the same for all ranks.) Almost any letter in the board part will stand for some piece, as next to images for the 6 orthodox chess pieces, it also has images for many fairy pieces.

'pgn' tags — When you put these around a PGN game notation, the pgn4web game viewer will be embedded in your posting to display the game. This viewer has buttons that allow the reader to navigate through the game.

'diag' tags — These tags can be used to include an 'Interactive Diagram' into your posting. Such a diagram is basically an entire chess (variant) program; the position diagram it shows acts as a GUI, and you can switch on an AI that acts as a chess engine, albeit rather weak. So you can move pieces around with the mouse, and the diagram will highlight the square(s) where they can be moved to. And if the AI is on, (the 'Play it!' link below the diagram) it will reply to such moves with moves of its own. What has to be between the tags to achieve this is a bit complex, as it has to define both the graphical parameters of the diagram (e.g. colors), the board dimensions, the initial setup, how the participating pieces move (if they are non-standard), and other rule details. For more information on making such diagrams, please visit this link.

The editor for entering postings contains buttons for surrounding a selected text with fen or pgn tags.