also tag 'patch/core', considering that over half of the changes are there

[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]]

>> 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|ptecza]]

>>> Joey, will you add that plugin to Ikiwiki 2.61? :) --[[Paweł|ptecza]]

>>>> 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](http://kitenet.net/~joey/blog/entry/vacation/) :D
>>>>> It's GPL-2+ like your Ikiwiki and the most external plugins.
>>>>> --[[Paweł|ptecza]]

        --- /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 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]]