Chess By Blog is a plugin for WordPress 2.0 that adds graphical chess
functionality to your WordPress blog. It lets you do several things:
- The board supports interactive play directly in the browser, in a mode which does not update the post body. All rules of chess are supported, include en passant, castling, and pawn promotion. This can be used to present chess problems for readers to work through.
- Chess By Blog also supports a persistent game played between two players, hence the name of the plugin. Readers that have edit permissions on a post can take turns moving pieces, with the state of the board saving to the WordPress database between moves. The plugin uses WordPress and PHP security features to ensure that only moves that come from the client chessboard code can update the database.
Chess By Blog is free software, distributed under the Expat license (a copy of which is in chess-by-blog.php).
Examples of game play can be seen at the examples page.
Chess By Blog has been tested on WordPress 2.0.4 to 3.0; it is not supported for earlier versions.
Before installing, you should back up your WordPress blog, particularly if you intend to use the persistent game feature since this will make changes directly to your database. The changes should only be limited to the body of the post which contains the chess board, and I’m not aware of any issues with the code – but better safe than sorry.
The top level contents of the zip folder look like this:
/chess-by-blog +--readme.txt (this file!) +--chess-by-blog.php +--/chess-by-blog +----/themes +----(support files) +--/src
The top level chess-by-blog directory should simply be copied to your WordPress wp-content/plugins directory. Optionally, unless you are building the client side code yourself, you can delete the src directory.
You should now be able to activate the plugin from the WordPress Plugins administration panel.
The plugin adds a “Chess By Blog” to the Quicktag panel that appears when you edit or write a new post. (Unfortunately, at this time there is no corresponding button in the visual editor.) Clicking the button will pop open a new window which allows you to create a new chess board. The fields of this board correspond almost directly to the seven required tags of Portable Game Notation. For the purposes of the plugin, all fields are optional; accepting the defaults will result in code inserted into your post which will create an empty, closed board. There are three types of boards that can be set up:
- Static, non playable board
- A static, non playable board can be created by leaving the “WordPress ID” blank and by inserting algebraic move notation in the Movelist field. Note that for speed reasons, the input (particularly pawn moves) isn’t fully error checked by the client code.
- Playable, non-persistent board
- An interactive, non-persistent board can be created by leaving the White and Black players at the default (i.e. “*”). Algebraic move notation can be optionally inserted in the move text to set up the board. Note that when the board is played interactively, full validation of each move is performed. This mode is ideal for presenting chess problems that can be worked through by readers.
- Playable, persistent board
- An interactive and persistent board can be created by selecting blog users for the White and Black players. These should correspond to the usernames of users of your blog who have at least Subscriber Roles.
Alternately, you can forego the usage of the Quicktags button and insert PGN directly, enclosed in “div class=”CBB-board” tags. The client code will treat standard PGN as a static, non playable board. Playable boards can be created by inserting [CBBWhiteId] and [CBBBlackId] PGN tags with values as described above.
Chess By Blog fully supports the seven standard PGN tags. Comments enclosed with curly braces are preserved, and will be shown at the top of the game log table when the corresponding move is highlighted. In addition, the FEN and JsCom (only the “startply” command is recognized) tags are both supported, allowing specification of the initial board layout. As an example of the JsCom tag, specifying
[JsCom "startply 5"]
will preposition the board after White’s 3rd move.
Chess variant support
Chess By Blog fully supports FEN (Forsythe-Edwards Notation) via the “FEN” tag in PGN. This allows specification of the initial board layout. It also allows for handling of some chess variants.
Fischer Random Chess (or Chess960) is directly supported. The initial layout of the pieces must be specified via a FEN tag. Castling is supported correctly for this variant.
Capablanca chess is directly supported. The layout of the board must be specified via a FEN tag, using “A” or “a” for the Archbishop and “C” or “c” for the Chancellor; a 8×10 piece layout must be specified as well.
There is limited support for arbitrary board sizes. Castling is handled by always moving the King to the ‘c’ file if castling on the a side, or the file to the left of the rightmost file if castling on the other side; the Rook is always moved to the inner square. This supports Fischer Random Chess and Capablanca Random Chess, but does not support other variants. In addition, en passant always assumes the pawns start on the 3rd rank.
The look of the client side code is controlled by themes, which live under chess-by-blog/themes. A new theme can be created by adding a subdirectory which contains at least a file named “ChessByBlog.css”. This style sheet should contain the same classes as shown in the default theme. In addition, there is a requirement that the CBB-square and CBB-button contain width, height, and min-height attributes with explicit pixel sizes. The client side code needs these in order to correctly infer the sizes of chessboard squares and buttons.
Building the client side code
This step is optional, but if you need to make fundamental changes to the code that can’t covered by changes to CSS, you’ll need to edit the Java source files in src/org/levork/gwt.
webAppCreator -ignore org.levork.gwt.client.ChessByBlog
- Switching from the code to visual editor may wreak havoc on the div tags, despite the tags being protected by pre tags. This is an issue with the visual editor. Release of the plugin starting with 1.1.4 should be more immune to this problem on the client side.
- Internet Explorer may have update issues with the preview of new themes in the management panel, particularly if the theme resizes the square.
at the beginning of the file.