Recently I've wanted to colour some piece of text on my Ikiwiki page. It seems that Markdown can do it only using HTML tags, so I used <span class="color">foo bar baz</span>.

However, in my opinion mixing Markdown syntax and HTML tags is rather ugly, so maybe we should create a new color plugin to add more color to Ikiwiki ;) I know that another Wikis have similar plugin, for example WikiDot.

I've noticed that htmlscrubber plugin strips style attribute, because of security, so probably we need to use class attribute of HTML. But then we have to customize our local.css file to add all color we want to use. It's not as easy in usage like color name or definition as plugin argument, but I don't have a better idea right now.

What do you think about it? --Paweł

Making a plugin preserve style attributes can be done, it just has to add them after the sanitize step, which strips them. The general method is adding placeholders first, and replacing them with the real html later.

The hard thing to me seems to be finding a syntax that is better than a <span>. A preprocessor directive is not really any less ugly than html tags, though at least it could play nicely with nested markdown: --Joey

[[!color red,green """ Xmas-colored markdown here """]]

I'm glad you like that idea. In my opinion your syntax looks good. Out of curiosity, why did you used 2 colors in your example? What is HTML result for it? ;)

I was thinking one would be foreground, the other background. Don't know if setting the background makes sense or not.

I can try to create that plugin, if you are too busy now. I'm not Perl hacker, but I wrote a lot of Perl scripts in my life and color plugin doesn't seem to be very hard task. --Paweł

Yes, it's a good intro plugin, have at it! --Joey

This is a RC1 of my color plugin. It works for me well, but all your comments are very welcome. --Paweł

Sure, I have a couple.

Great! Thank you very much! --Paweł

The preprocess function is passed named parameters. The hack you have of hardcoding use of $_[0] and $_[2] can fail at any time.

But the problem is that arguments of my plugin don't have a name. How can I identify them in params hash?

Similar hardcoded method I've found in img plugin :) But only one argument is not named there (image path).

I think I hadn't realized what you were doing there. The order for unnamed parameters can in fact be relied on.

--Joey

Maybe I shouldn't use so simple plugin syntax? For following syntax I wouldn't have that problem:

[[!color  fg=white bg=red text="White text on red background"]]

replace_preserved_style is passed a single parameter, so its prototype should be ($), not (@). Ditt preserve_style, it should have ($$).

OK, it will be fixed.

The sanitize hook is always passed $params{content}, so there should be no reason to check that it exists. Also, it shouldn't be done in a sanitize hook, since html sanitization could run after that santize hook. It should use a format hook.

Probably you're right. It was rather paranoid checking ;) Thanks for the hook hint!

The preprocess hook needs to call IkiWiki::preprocess on the content passed into it if you want to support nesting other preprocessor directives inside the color directive. See preprocess_toggleable in the toggle plugin, for example.

I'm not a big fan of the dummy text COLORS { ... } SROLOC;TEXT { ... TXET } The method used by toggle of using two real <div>s seems slightly better. --Joey

I don't like that too, but I didn't have better idea :) Thank you for the hint! I'll take a look at toggle plugin.

And here is RC2 of that plugin. I've changed a plugin syntax, because the old seems to be too enigmatic and it was hard to me to handle unnamed parameters in not hardcoded way. I hope that my changes are acceptable for you. Of course, I'm open for discussion or exchange of ideas :) --Paweł

One question, why the 2px padding for span.color? --Joey

Sorry for a long silence, but I had Internet free summer holiday :) I did that, because backgrounded text without any padding looks strange for me ;) You can remove it if you don't like that padding. --Paweł

Joey, will you add that plugin to Ikiwiki 2.61? :) --Paweł

I also had a long net-free summer holiday. :-) The patch is ready for integration (made a few minor changes). Is this GPL 2? --Joey

No problem. I guessed it, because I've not seen your commits at RecentChanges page in last days and I subscribe your blog :D It's GPL-2+ like your Ikiwiki and the most external plugins. --Paweł

--- /dev/null   2008-06-21 02:02:15.000000000 +0200
+++ color.pm    2008-07-27 14:58:12.000000000 +0200
@@ -0,0 +1,69 @@
+#!/usr/bin/perl
+# Ikiwiki text colouring plugin
+# Paweł‚ Tęcza <ptecza@net.icm.edu.pl>
+package IkiWiki::Plugin::color;
+
+use warnings;
+use strict;
+use IkiWiki 2.00;
+
+sub import {
+   hook(type => "preprocess", id => "color", call => \&preprocess);
+   hook(type => "format",     id => "color", call => \&format);
+}
+
+sub preserve_style ($$$) {
+   my $foreground = shift;
+   my $background = shift;
+   my $text       = shift;
+
+   $foreground = defined $foreground ? lc($foreground) : '';
+   $background = defined $background ? lc($background) : '';
+   $text       = '' unless (defined $text);
+
+   # Validate colors. Only color name or color code are valid.
+   $foreground = '' unless ($foreground &&
+               ($foreground =~ /^[a-z]+$/ || $foreground =~ /^#[0-9a-f]{3,6}$/));
+   $background = '' unless ($background &&
+               ($background =~ /^[a-z]+$/ || $background =~ /^#[0-9a-f]{3,6}$/));
+
+   my $preserved = '';
+   $preserved .= '<span class="color">';
+   $preserved .= 'color: '.$foreground if ($foreground);
+   $preserved .= '; ' if ($foreground && $background);
+   $preserved .= 'background-color: '.$background if ($background);
+   $preserved .= '</span>';
+   $preserved .= '<span class="colorend">'.$text.'</span>';
+   
+   return $preserved;
+
+}
+
+sub replace_preserved_style ($) {
+   my $content = shift;
+
+   $content =~ s!<span class="color">((color: ([a-z]+|\#[0-9a-f]{3,6})?)?((; )?(background-color: ([a-z]+|\#[0-9a-f]{3,6})?)?)?)</span>!<span class="color" style="$1">!g;
+   $content =~ s!<span class="colorend">!!g;
+
+   return $content;
+}
+
+sub preprocess (@) {
+   my %params = @_;
+
+   # Preprocess the text to expand any preprocessor directives
+   # embedded inside it.
+   $params{text} = IkiWiki::preprocess($params{page}, $params{destpage},
+               IkiWiki::filter($params{page}, $params{destpage}, $params{text}));
+
+   return preserve_style($params{foreground}, $params{background}, $params{text});
+}
+
+sub format (@) {
+   my %params = @_;
+
+   $params{content} = replace_preserved_style($params{content});
+   return $params{content};    
+}
+
+1
--- /dev/null   2008-06-21 02:02:15.000000000 +0200
+++ color.mdwn  2008-07-27 15:04:42.000000000 +0200
@@ -0,0 +1,25 @@
+[[!template  id=plugin name=color core=0 author="<a href="../../users/ptecza/">ptecza</a>"]]
+
+This plugin can be used to color a piece of text on a page.
+It can be used to set the foreground and/or background color of the text.
+
+You can use a color name (e.g. `white`) or HTML code (e.g. `#ffffff`)
+to define colors. 
+
+Below are a few examples:
+
+    [[!color  foreground=white background=#ff0000 text="White text on red background"]]
+
+In the above example, the foreground color is defined as a word, while the background color is defined as a HTML
+color code.
+
+    [[!color  foreground=white text="White text on default color background"]]
+
+The background color is missing, so the text is displayed on default background.
+
+    [[!color  background=#ff0000 text="Default color text on red background"]]
+
+The foreground is missing, so the text has the default foreground color.
--- style.css-orig  2008-07-27 15:12:39.000000000 +0200
+++ style.css   2008-07-27 15:15:06.000000000 +0200
@@ -333,3 +333,7 @@
    background: #eee; 
    color: black !important;
 }
+
+span.color {
+   padding: 2px;
+}

done