From 2b0c8d167e8b98d11e3504393fe4b98596dfd891 Mon Sep 17 00:00:00 2001
From: Simon McVittie <smcv@ http://smcv.pseudorandom.co.uk/>
Date: Thu, 18 Jun 2009 18:25:46 +0100
Subject: [PATCH 1/3] pagestats: when making a tag cloud, don't emit links
 where the tag is unused

---
 IkiWiki/Plugin/pagestats.pm | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/IkiWiki/Plugin/pagestats.pm b/IkiWiki/Plugin/pagestats.pm
index 8ab5d3666..5dd2f337b 100644
--- a/IkiWiki/Plugin/pagestats.pm
+++ b/IkiWiki/Plugin/pagestats.pm
@@ -63,6 +63,8 @@ sub preprocess (@) {
 
 		my $res = "<div class='pagecloud'>\n";
 		foreach my $page (sort keys %counts) {
+			next unless $counts{$page} > 0;
+
 			my $class = $classes[$counts{$page} * scalar(@classes) / ($max + 1)];
 			$res .= "<span class=\"$class\">".
 			        htmllink($params{page}, $params{destpage}, $page).

From 9c13e29d4fbb85a83b0ed5fd7271d7c1688fbc07 Mon Sep 17 00:00:00 2001
From: Simon McVittie <smcv@ http://smcv.pseudorandom.co.uk/>
Date: Thu, 18 Jun 2009 18:27:00 +0100
Subject: [PATCH 2/3] IkiWiki::Render: split out backlink_pages() function from
 backlinks()

This separates style from content - backlinks() performs lossy
transformations on the page names to get it in the form that the page
template wants.
---
 IkiWiki/Render.pm | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/IkiWiki/Render.pm b/IkiWiki/Render.pm
index 2da18738d..6900d5eed 100644
--- a/IkiWiki/Render.pm
+++ b/IkiWiki/Render.pm
@@ -24,13 +24,19 @@ sub calculate_backlinks () {
 	$backlinks_calculated=1;
 }
 
-sub backlinks ($) {
+sub backlink_pages ($) {
 	my $page=shift;
 
 	calculate_backlinks();
 
+	return keys %{$backlinks{$page}};
+}
+
+sub backlinks ($) {
+	my $page=shift;
+
 	my @links;
-	foreach my $p (keys %{$backlinks{$page}}) {
+	foreach my $p (backlink_pages($page)) {
 		my $href=urlto($p, $page);
                 
 		# Trim common dir prefixes from both pages.

From acb79b5c00b48c4b52a29703e9d7b52330fd23b2 Mon Sep 17 00:00:00 2001
From: Simon McVittie <smcv@ http://smcv.pseudorandom.co.uk/>
Date: Thu, 18 Jun 2009 18:33:49 +0100
Subject: [PATCH 3/3] pagestats: add `among` parameter, which only counts links
 from specified pages

---
 IkiWiki/Plugin/pagestats.pm          | 11 ++++++++++-
 doc/ikiwiki/directive/pagestats.mdwn | 10 ++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/IkiWiki/Plugin/pagestats.pm b/IkiWiki/Plugin/pagestats.pm
index 5dd2f337b..874ead7e6 100644
--- a/IkiWiki/Plugin/pagestats.pm
+++ b/IkiWiki/Plugin/pagestats.pm
@@ -38,13 +38,22 @@ sub preprocess (@) {
 	# Needs to update whenever a page is added or removed, so
 	# register a dependency.
 	add_depends($params{page}, $params{pages});
+	add_depends($params{page}, $params{among}) if exists $params{among};
 	
 	my %counts;
 	my $max = 0;
 	foreach my $page (pagespec_match_list([keys %links],
 			$params{pages}, location => $params{page})) {
 		use IkiWiki::Render;
-		$counts{$page} = scalar(IkiWiki::backlinks($page));
+
+		my @backlinks = IkiWiki::backlink_pages($page);
+
+		if (exists $params{among}) {
+			@backlinks = pagespec_match_list(\@backlinks,
+				$params{among}, location => $params{page});
+		}
+
+		$counts{$page} = scalar(@backlinks);
 		$max = $counts{$page} if $counts{$page} > $max;
 	}
 
diff --git a/doc/ikiwiki/directive/pagestats.mdwn b/doc/ikiwiki/directive/pagestats.mdwn
index cfb5737a5..426f3e4af 100644
--- a/doc/ikiwiki/directive/pagestats.mdwn
+++ b/doc/ikiwiki/directive/pagestats.mdwn
@@ -12,4 +12,14 @@ And here's how to create a table of all the pages on the wiki:
 
 	\[[!pagestats style="table"]]
 
+The optional `among` parameter limits counting to pages that match a
+[[ikiwiki/PageSpec]]. For instance, to display a cloud of tags used on blog
+entries, you could use:
+
+	\[[!pagestats pages="tags/*" among="blog/posts/*"]]
+
+or to display a cloud of tags related to Linux, you could use:
+
+	\[[!pagestats pages="tags/* and not tags/linux" among="tagged(linux)"]]
+
 [[!meta robots="noindex, follow"]]