ikiwiki/doc/todo/color_plugin.mdwn

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](http://www.wikidot.com/).

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|ptecza]]

> 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|ptecza]]

>> 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|ptecza]]

> Sure, I have a couple.

>> Great! Thank you very much! --[[Paweł|ptecza]]

> 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|ptecza]]

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

	--- /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="[[ptecza]]"]]
	+
	+This plugin can be used to color a piece of text on Ikiwiki page.
	+It's possible setting foreground and/or background color of the text.
	+
	+You can use name (e.g. `white`) or HTML code of colors (e.g. `#ffffff`)
	+to define colors. 
	+
	+Below are a few examples:
	+
	+    \[[!color foreground=white background=#ff0000 text="White text on red background"]]
	+
	+Foreground color is defined as a word, background color is defined as HTML
	+color code.
	+
	+    \[[!color foreground=white text="White text on default color background"]]
	+
	+Background color is missing, so the text is displayed on default background.
	+
	+    \[[!color background=#ff0000 text="Default color text on red background"]]
	+
	+Foreground is missing, so the text has default color.
	+
	+This plugin is not enabled by default. You can do that in [[ikiwiki.setup]]
	+file (hint: `add_plugins` variable).
	--- 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;
	+}