You can also include extra parameters after the fen code, just as you would in a query string, because it's just going to plug your FEN code into a query string.
A smart and convenient trick. This means we really don't need the 'cols' and 'set' shortcodes. The latter doesn't seem to be working anyway.
The purpose, however, is to make it as easy as possible for a noob user, who doesn't know the ins and outs of the Diagram Designer, and probably doesn't even know it exists. We cannot expect such users to know the 'cols' keyword, or query-string syntax, the 'set' keyword or the names of the available sets, etc. So it is important that we invoke the Diagram Designer with the most useful default values. To which we then append &code= plus the string between the fen tags. This would still allow 'power users' to overrule the defaults by adding parameters at the end of the FEN in query-string syntax, as in case of duplicat specification of a key, the one encountered latest will prevail.
set - I think auto-alfaeriePNG35 would be the best default here, (or an equivalent overly large set forced to display at reduced size) because:
It has the largest number of pieces.
It is small, allowing representation of large boards without problems.
Orthodox pieces use their conventional icons, which each chess player will recognize.
Pieces can be indicated by {name}. Apart from the orthodox pieces there are no universal single-letter abbreviations for chess pieces, and the alphabet is not large enough anyway, so non-obvious abbreviations would be more the rule than the exception. Users would know that they wanted a camel, giraffe or rhino, but even if these had letters assigned to them, these would not be C (cannon), G (griffon) or R (rook), and the users would be clueless as to what letter to use.
For compactness the orthodox pieces and most-common fairies (Archbishop, Cannon, Elephant, Griffon, Marshall) can also be indicated with a single letter.
cols - This still should be automated. I propose to treat a setting cols=10000 (or some other large value that can never be used in practice) on the Diagram Designer as a special value, which would derive the true value from the length of the first row of the FEN in the code parameter. This would not interfere with the normal processing during the first row because it will be large enough to never make the board 'wrap' to the next rank automatically. And when the first slash is encountered, before padding the rank with 'holes', it can set $cols to the current length of the rank if it was 10000, and then proceed as normal. The fen shortcode can then invoke the DD with the parameter cols=10000.
colors - This is more a matter of taste, but I feel that the default colors are a bit 'loud' for embedded diagrams that only serve as illustration for what is explained in the surrounding text. I would prefer 'softer'colors (with a somewhat lower saturation), and a less prominant board margin, like
A smart and convenient trick. This means we really don't need the 'cols' and 'set' shortcodes. The latter doesn't seem to be working anyway.
The purpose, however, is to make it as easy as possible for a noob user, who doesn't know the ins and outs of the Diagram Designer, and probably doesn't even know it exists. We cannot expect such users to know the 'cols' keyword, or query-string syntax, the 'set' keyword or the names of the available sets, etc. So it is important that we invoke the Diagram Designer with the most useful default values. To which we then append &code= plus the string between the fen tags. This would still allow 'power users' to overrule the defaults by adding parameters at the end of the FEN in query-string syntax, as in case of duplicat specification of a key, the one encountered latest will prevail.
set - I think auto-alfaeriePNG35 would be the best default here, (or an equivalent overly large set forced to display at reduced size) because:
cols - This still should be automated. I propose to treat a setting cols=10000 (or some other large value that can never be used in practice) on the Diagram Designer as a special value, which would derive the true value from the length of the first row of the FEN in the code parameter. This would not interfere with the normal processing during the first row because it will be large enough to never make the board 'wrap' to the next rank automatically. And when the first slash is encountered, before padding the rank with 'holes', it can set $cols to the current length of the rank if it was 10000, and then proceed as normal. The fen shortcode can then invoke the DD with the parameter cols=10000.
colors - This is more a matter of taste, but I feel that the default colors are a bit 'loud' for embedded diagrams that only serve as illustration for what is explained in the surrounding text. I would prefer 'softer'colors (with a somewhat lower saturation), and a less prominant board margin, like
Other proposals are of course welcome.