Command/defineitemgroup

Defining lists

Defining Template:\itemize like *itemgroups* is accomplished through Template:\defineitemgroup and the correspoding setup. For historical reasons these have a non-standard, duplicate interface requiring some options to be specified as key-value setups, others as an argument list.

\defineitemgroup [myitems] \setupitemgroup [myitems] [each] [joinedup] \setupitemgroup [myitems] [each] [itemalign=flushright]

The second argument determines the itemization level the settings apply to.

The third argument comes in two varieties.

Parameters that concern whitespace (both vertical and horizontal) belong in the argument list: joinedup, packed, nowhite and the likes.

Further options are part of the setup. Both kinds can be given in a combined version:

\setupitemgroup [myitems] [each] [joinedup] [itemalign=flushright]

Custom bullets

Bullets are very flexible. They hook into the Template:\symbol mechanism.

The macro generator here is Template:\definesymbol. Basically it allows for all valid Context code to appear inside the definition, including the list item counter. This counter can be accessed via Template:\currentitemnumber. To achieve the “item number in a box” effect we have to draw this number as the contents of the box like so:

The Template:\framed must be adapted to the specific requirements.

Putting it together

Below listing combines all the above into one working example.

    \unprotect
    
    %% the bullet: a red square
    
    \defineframed [instruction_symbol_frame] [
      background=color,
      backgroundcolor=red,
      frame=off,
      width=1em,
      height=\framedparameter{width}, %% -> let height = width
    ]
    
    %% bare bullet
    
    \definesymbol [instruction_symbol]
      [{\instruction_symbol_frame{\strut}}]
    
    %% same bullet, with item number inside
    
    \definesymbol [instruction_symbol_numbered]
      [{\instruction_symbol_frame{\currentitemnumber}}]
    
    %% define the “regular“ itemization with a red box as bullet indicator
    
    \defineitemgroup [RegularList]
    \setupitemgroup [RegularList] [each] [joinedup]
    \setupitemgroup [RegularList] [symbol=instruction_symbol]
    
    %% define the “Instructions” type itemization that includes the item
    %% number inside the box
    
    \defineitemgroup [Instructions]
    \setupitemgroup [Instructions] [each] [joinedup]
    \setupitemgroup [Instructions] [symbol=instruction_symbol_numbered]
    
    \protect
    
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    %% demo
    
    \starttext
      Chemicals
      \startRegularList
        \startitem \input knuth \stopitem
        \startitem \input ward \stopitem
      \stopRegularList
    
      \blank [2*big]
    
      Instructions
      \startInstructions
        \startitem \input knuth \stopitem
        \startitem \input ward \stopitem
      \stopInstructions
    \stoptext