Annotation of docbook2mdoc/README, Revision 1.5
1.5 ! schwarze 1: $Id: README,v 1.4 2019/04/06 13:30:21 schwarze Exp $
1.1 kristaps 2:
3: Here's a quick note on how to add new DocBook elements.
4:
1.2 schwarze 5: First, look up the element in the DocBook reference.
6: For element <foo>, this is usually:
1.1 kristaps 7:
1.2 schwarze 8: https://tdg.docbook.org/tdg/5.1/foo.html
9:
10: Some elements are no longer defined in DocBook 5.
11: For these, you will have to look at 4.5 documentation instead:
12:
13: https://tdg.docbook.org/tdg/4.5/foo.html
1.1 kristaps 14:
15:
1.4 schwarze 16: Add one "struct element" initializer to the elements[] array in the
17: file parse.c, containing the name of element as it appears in DocBook
18: documents and the "enum nodeid" constant of the node to be generated.
19: There are several special cases:
20:
21: * If docbook2mdoc(1) never needs to produce any output for the
22: element nor from any children it may have, specify NODE_DELETE.
23: If, in addition, finding the element in an input document implies
24: that the output from the document will likely be incomplete or
25: otherwise significantly unsatisfactory, use NODE_DELETE_WARN
26: instead.
27:
28: * If docbook2mdoc(1) can treat the element as transparent, that
29: is, if removing the element and inserting its content in its
30: place would not change the desired formatting, specify NODE_IGNORE.
31: This does not exclude that in DocBook itself, syntactic requirements
32: or semantic significance may be attached to the element.
33:
34: * If docbook2mdoc(1) can handle the element in exactly the same way
35: as another node that is already handled, reuse the "enum nodeid"
36: constant for the node that is already handled. This only requires
37: identitical handling by docbook2mdoc(1), even when syntax or
38: semantics differ in DocBook itself. For example:
39: { "chapter", NODE_SECTION },
40: { "part", NODE_SECTION },
41: { "refsect1", NODE_SECTION },
42: { "refsect2", NODE_SECTION },
43: /* ... */
44: { "section", NODE_SECTION },
45:
46: * Otherwise - that is, when the formatter needs to make at least
47: one explicit formatting decision based on the presence, absence,
48: or content of the element - add an enum constant for the new
49: node to the declaration of "enum nodeid" in the file node.h.
50: Preserve the alphabetic ordering.
51: Add such a constant if only if the code will use it at least at
52: one place in addition to the definition of the elements[] array.
53:
54:
55: In the latter case, implement formatting in the file docbook2mdoc.c.
56: Decide how the new node needs to be handled in the first, bigger
57: switch statement of the function pnode_print(). Typical cases
58: include:
59:
60: * Nodes to be represented by in-line macros that are parsed and
61: callable often get away with merely opening a macro scope
62: with macro_open(), letting the subsequent loop take care of
1.5 ! schwarze 63: any children.
1.4 schwarze 64:
65: * Nodes to be represented by one single stand-alone macro sometimes
66: get away with calling macro_line(), or macro_nodeline() if an
67: argument is required.
68:
69: * Nodes with complex formatting requirements call their own,
70: dedicated pnode_print*() formatting functions.
71: These functions are ordered roughly as follows:
72: 1. paragraphs
73: 2. sections
74: 3. functions and mathematics
75: 4. semantic markup for command line utilities
76: 5. various semantic markup
77: 6. structural markup like lists and tables
78: Such functions often contain their own loops over children and
79: remove the children with pnode_unlinksub() at the end. But in
80: some cases, it is alternatively possible to let the common loop
81: in the middle of pnode_print() handle the children.
82:
83:
84: Always keep the distinction between the two main ways to handle
85: children in mind: by default and by the common loop in the middle
86: of pnode_print(), children are formatted recursively with pnode_print(),
87: potentially resulting in complex, nested formatting. By contrast,
88: children can be reduced to just one string containing their their
89: bare text content, ignoring any further markup that may be contained
90: inside, by calling macro_addnode(), macro_nodeline(), or print_textnode().
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