brittany/docs/implementation/bridoc-api.md

BriDoc nodes/Smart constructors and their semantics

At this point, you should have a rough idea of what the involved types mean. This leaves us to explain the different BriDoc (smart) constructors and their exact semantics.

Special nodes

• docDebug/BDDebug

  Like the trace statement of the BriDoc type. It does not affect the normal output, but prints stuff to stderr when the transformation traverses this node.

• BDExternal is used for original-source reproduction.

Basic nodes

• docEmpty/BDEmpty Text

  ""

  The empty document. Has empty output. Should never affect layouting.

• docLit/BDLit

  "a" "Maybe" "("

  The most basic building block - a simple string. Has nothing to do with literals in the parsing sense. Will always be produces as-is in the output. It must be free of newline characters and should normally be free of any spaces (because those would never be considered for line-breaking - but there are cases where this makes sense still).

• docSeq/BDSeq [BriDoc]

  "func foo = 13"

  A in-line/horizontal sequence of sub-docs. The sub-documents should not contain any newlines, but there is an exception: The last element of the sequence may be multi-line. In combination with docSetBaseY this allows for example:

  foo | bar = 1
      | baz = 2
  

  which is represented roughly like

  docSeq
    "foo"
    space
    docSetBaseY
      docLines
        stuff that results in "| bar = 1"
        stuff that results in "| baz = 2"
  

  But in general it should be preferred to use docPar to handle multi-line sub-nodes, where possible.

• docAlt/BDAlt [BriDoc]

  Specify multiple alternative layouts. Take care to appropriately maintain sharing for the documents representing the children of the current node.

• docAltFilter

  simple utility wrapper around docAlt: Each alternative is accompanied by a boolean; if False the alternative is discarded.

• docPar/BDPar

  TODO

• docLines/BDLines

  TODO

• docSeparator/BDSeparator

  Adds a space, unless it is the last element in a line. Also merges with other separators and has no effect if inserted right after inserting space (e.g. in the start of a line when indented) or if already indented due to horizontal alignment.

Creating horizontal alignment

• docCols/BDCols ColSig [BriDoc]

  This works like docSeq, but adds horizontal alignment if possible. The implementation involves a lot of special-case trickeries and I assume that it is impossible to specify the exact semantics. But the rough idea is: If

  1. horizontal alignment is not turned off via global config
  2. there are consecutive lines (created e.g. by docLines or docPar) and
  3. both lines consist of docCols (where "consist" can ignore certain shallow wrappers like docAddBaseY) and
  4. the two ColSigs are equal and
  5. the two docCols contain an equal number of children and
  6. there is enough horizontal space to insert the additional spaces

  then the contained docs will be aligned horizontally.

  And further, if there are multiple lines so that consecutive pairs fulfill these requirements, the whole block will be aligned to the same horizontal tabs.

  And further, if a docCols contains another docCols, and the docCols in the next line also does, and the child docCols also match in ColSigs and have the same number of arguments and so on, then the children's children are also aligned horizontally.

  And of course this nesting also works over blocks built of matching consecutive pairs.

  Wait, was this not supposed to be broadly simplifying? Well.. it is. uhm. Let us just.. example.. an example seems fine.

  Considering the following declaration/formatting:

  func (MyLongFoo abc def) = 1
  func (Bar       a   d  ) = 2
  func _                   = 3
  

  Note how the "=" are aligned over all three lines, and the patterns in the first two lines are as well, but the pattern in the third line is just a structureless underscore?

  The representation behind that source is something in the direction of this (heavily simplified and not exact at all; e.g. spaces are not represented at all):

  docLines
    docCols equation
      "func"
      docCols
        "("
        "MyLongFoo"
        "abc"
        "def"
        ")"
      docSeq
        "="
        "1"
    docCols equation
      "func"
      docCols
        "("
        "Bar"
        "a"
        "d"
        ")"
      docSeq
        "="
        "2"
    docCols equation
      "func"
      "_"
      docSeq
        "="
        "3"
  

Controlling indentation level

TODO

• docAddBaseY/BDAddBaseY
• docSetBaseY
• docSetIndentLevel
• docSetBaseAndIndent
• docEnsureIndent

Controlling layouting

TODO

• docNonBottomSpacing
• docSetParSpacing
• docForceParSpacing
• docForceSingleline
• docForceMultiline

Inserting comments / Controlling comment placement

TODO

• docAnnotationPrior
• docAnnotationKW
• docAnnotationRest

Deprecated

• BDForwardLineMode is unused and apparently should be deprecated.
• BDProhibitMTEL is deprecated