1 [[!template id=gitbranch branch=smcv/sort-hooks author="[[Simon_McVittie|smcv]]"]]
4 The available [[ikiwiki/pagespec/sorting]] methods are currently hard-coded in
5 IkiWiki.pm, making it difficult to add any extra sorting mechanisms. I've
6 prepared a branch which adds 'sort' as a hook type and uses it to implement a
7 new `meta_title` sort type.
9 Someone could use this hook to make `\[[!inline sort=title]]` prefer the meta
10 title over the page name, but for compatibility, I'm not going to (I do wonder
11 whether it would be worth making sort=name an alias for the current sort=title,
12 and changing the meaning of sort=title in 4.0, though).
15 <http://git.pseudorandom.co.uk/smcv/ikiwiki.git?a=shortlog;h=refs/heads/sort-hooks>
17 I briefly tried to turn *all* the current sort types into hook functions, and
18 have some of them pre-registered, but decided that probably wasn't a good idea.
19 That earlier version of the branch is also available for comparison:
21 <http://git.pseudorandom.co.uk/smcv/ikiwiki.git?a=shortlog;h=refs/heads/sort-hooks-excessive>
23 (The older version is untested, and probably doesn't really work as-is - I
24 misunderstood the details of how the built-in function `sort` works when using
25 `$a` and `$b`. The newer version has been tested, and has a regression test for
26 its core functionality.)
28 This hook *isn't* (yet) sufficient to implement [[plugins/contrib/report]]'s
29 NIH'd sorting mechanisms:
31 * `report` can sort by any [[plugins/contrib/field]], whereas this one has a
32 finite number of hooks: if the `field` plugin's functionality is desirable,
33 perhaps parameterized sort mechanisms similar to pagespec match functions
34 would be useful? Then the `field` plugin could register
35 `hook(type => "sort", id => "field")` and you could have
36 `\[[!inline ... sort="field(Mood)"]]` or something?
38 * `report` can sort by multiple criteria, with independent direction-changing:
39 if this is desirable, perhaps `pagespec_match_list` could be enhanced to
40 interpret `sort="x -y z(w)"` as sorting by (pseudocode)
41 `{ $cmp_x->($a, $b) || (-$cmp_y->($a, $b)) || $cmp_z->($a, $b, "w") }`?
43 > I've now added both of these features to the sort-hooks branch. --[[smcv]]
45 >> I wonder if IkiWiki would benefit from the concept of a "sortspec", like a [[ikiwiki/PageSpec]] but dedicated to sorting lists of pages rather than defining lists of pages? Rather than defining a sort-hook, define a SortSpec class, and enable people to add their own sort methods as functions defined inside that class, similarly to the way they can add their own pagespec definitions. --[[KathrynAndersen]]
47 >>> [[!template id=gitbranch branch=smcv/sort-package author="[[Simon_McVittie|smcv]]"]]
48 >>> I'd be inclined to think that's overkill, but it wasn't very hard to
49 >>> implement, and in a way is more elegant. I set it up so sort mechanisms
50 >>> share the `IkiWiki::PageSpec` package, but with a `cmp_` prefix. Gitweb:
51 >>> <http://git.pseudorandom.co.uk/smcv/ikiwiki.git?a=shortlog;h=refs/heads/sort-package>
53 ## Documentation from sort-hooks branch
55 ### sort hook (added to [[plugins/write]])
57 hook(type => "sort", id => "foo", call => \&sort_by_foo);
59 This hook adds an additional [[ikiwiki/pagespec/sorting]] order or overrides
62 The callback is given two page names followed by the parameter as arguments, and
63 returns negative, zero or positive if the first page should come before,
64 close to (i.e. undefined order), or after the second page.
66 For instance, the built-in `title` sort order could be reimplemented as
69 pagetitle(basename($_[0])) cmp pagetitle(basename($_[1]));
72 and to sort by an arbitrary `meta` value, you could use:
74 # usage: sort="meta(description)"
77 error "sort=meta requires a parameter" unless defined $param;
78 my $left = $pagestate{$_[0]}{meta}{$param};
79 $left = "" unless defined $left;
80 my $right = $pagestate{$_[1]}{meta}{$param};
81 $right = "" unless defined $right;
82 return $left cmp $right;
86 ### meta_title sort order (conditionally added to [[ikiwiki/pagespec/sorting]])
88 * `meta_title` - Order according to the `\[[!meta title="foo" sort="bar"]]`
89 or `\[[!meta title="foo"]]` [[ikiwiki/directive]], or the page name if no
92 ### Multiple sort orders (added to [[ikiwiki/pagespec/sorting]])
94 In addition, you can combine several sort orders and/or reverse the order of
95 sorting, with a string like `age -title` (which would sort by age, then by
96 title in reverse order if two pages have the same age).
98 ### meta title sort parameter (added to [[ikiwiki/directive/meta]])
100 An optional `sort` parameter will be used preferentially when
101 [[ikiwiki/pagespec/sorting]] by `meta_title`:
103 \[[!meta title="The Beatles" sort="Beatles, The"]]
105 \[[!meta title="David Bowie" sort="Bowie, David"]]
107 ## Documentation from sort-hooks branch
109 The changes to [[ikiwiki/pagespec/sorting]] are the same.
110 The changes to [[plugins/write]] are replaced by:
114 Similarly, it's possible to write plugins that add new functions as
115 [[ikiwiki/pagespec/sorting]] methods. To achieve this, add a function to
116 the IkiWiki::PageSpec package named `cmp_foo`, which will be used when sorting
117 by `foo` or `foo(...)` is requested.
119 The function will be passed three or more parameters. The first two are
120 page names, and the third is `undef` if invoked as `foo`, or the parameter
121 `"bar"` if invoked as `foo(bar)`. It may also be passed additional, named
124 It should return the same thing as Perl's `cmp` and `<=>` operators: negative
125 if the first argument is less than the second, positive if the first argument
126 is greater, or zero if they are considered equal. It may also raise an
127 error using `error`, for instance if it needs a parameter but one isn't
130 You can also define a function called `check_cmp_foo` in the same package.
131 If you do, it will be called while preparing to sort by `foo` or `foo(bar)`,
132 with argument `undef` or `"bar"` respectively; it may raise an error using
133 `error`, if sorting like that isn't going to work.