ikiwiki/doc/todo/pagedown_plugin/discussion.mdwn

(This conversation was moved from [[plugins/wmd/discussion]]. --[[anarcat]])

I've tried to retrieve the wmd-editor source tarball lately, but the site seems offline.

From what I've read on the Internet, wmd-editor is not (yet?) free software by itself, and its author has gone MIA.
But it looks like somebody recently took the step to rewrite a wmd-clone under a saner license, see [[pagedown|http://code.google.com/p/pagedown/source/browse/]].

Given all the above, what about upgrading this plugin to use pagedown instead of wmd? It seem a clear win to me...

> AFAICS, pagedown is a modified version of WMD. Let's 
> look at its license file: --[[Joey]] 
> 
>     A javascript port of Markdown, as used on Stack Overflow
>     and the rest of Stack Exchange network.
>     
>     Largely based on showdown.js by John Fraser (Attacklab).
>     
>     Original Markdown Copyright (c) 2004-2005 John Gruber
>       <http://daringfireball.net/projects/markdown/>
>     
>     
>     Original Showdown code copyright (c) 2007 John Fraser
>     
>     Modifications and bugfixes (c) 2009 Dana Robinson
>     Modifications and bugfixes (c) 2009-2011 Stack Exchange Inc.
>     
>     Permission is hereby granted, free of charge, to any person obtaining a
>     copy [...]
>     
> Ok, so it says it's based on showdown. John Fraser wrote showdown and also 
> WMD, which IIRC was built on top of showdown. (Showdown converts the
> markdown to html, and WMD adds the editor UI.)
> 
> I can nowhere find a actual statement of the copyright of showdown or
> WMD. <http://code.google.com/p/wmd/> has a "MIT License" notice on it,
> but this is clearly just the license chosen when signing up at google
> code for the repo that would be used for a rewrite of the code, and the only thing 
> said about the previous 1.0 release of WMD is "use it freely", which is not
> specific enough to be a grant of license, and is moreover not a free
> software license, as it does not cover distribution or modification.
> 
> Which was all covered in the thread here, 
> when StackOverflow decided to start working on pagedown.
> <http://blog.stackoverflow.com/2008/12/reverse-engineering-the-wmd-editor/>
> This thread does not give any indication that they ever managed to get
> a license grant for WMD/showdown. It frankly, does not inspire confidence
> that the people working on this care about the license.
> 
> It would probably be pretty easy to adapt the ikiwiki wmd plugin 
> to use pagedown. But without a clear and credible license, why?
> 
> (Note that I have a wmd-new branch in my ikiwiki git repo that
> uses <https://github.com/derobins/wmd>, which was an earlier
> version of pagedown (probably, not entirely clear).)
> 
> An alternate alternative is markitup: <http://markitup.jaysalvat.com/>
> It has a clear history and a credible license (MIT or GPL dual license).
> It's also easily extensible to other formats so could handle rst etc.
> It does not, however, have a markdown to html converter -- for 
> previewing it has to talk to the server with AJAX.
> --[[Joey]]


>> Showdown has a pretty explicit [license.txt file](https://github.com/coreyti/showdown/blob/master/license.txt)
>> and it basically looks like a BSD license. That license.txt file was imported into 
>> github directly from the upstream showdown source, so it seems credible. That zip file
>> is still available [on archive.org](http://wayback.archive.org/web/20100612163302/http://attacklab.net/showdown/showdown-v0.9.zip),
>> and does mention a BSD copyright.
>>
>> So Showdown itself is clean: it's free. Nowhere does it say it derives from WMD, or
>> if it does, it doesn't matter *because* it was made by the same author **and then** 
>> released under that free license. But even then, it does *not* mention being a
>> derivative of WMD.
>> 
>> I agree the license behind WMD is murky. One the one hand, the [google code page](https://code.google.com/p/wmd/)
>> mentions the code will be relicensed under MIT but "for now" we can "use it freely":
>> 
>> > *I'm refactoring the code, and will be releasing WMD under the MIT license soon. For
>> now you can download the most recent release (wmd-1.0.1.zip) and use it freely.*
>>
>> That zip file is again offline, but it's also [on archive.org](http://web.archive.org/web/20101226145228/http://wmd-editor.com/downloads/wmd-1.0.1.zip).
>> Things get a little more murky there: the file doesn't actually mention any copyright 
>> statement, and the code is actually obfuscated, something that is mentionned on the aforementionned
>> Stack Exchange thread. The [terms and conditions of WMD](http://web.archive.org/web/20100323043113/http://wmd-editor.com/terms)
>> are pretty hostile however:
>>
>>> *All rights reserved. You may not duplicate, copy, or reuse any portion of the HTML/CSS, JavaScript, or visual design elements or concepts without express written permission from AttackLab.*
>>
>> But one could argue they apply only to WMD, and *not* showdown, which has been
>> explicitely published under a different license. And maybe that was the whole 
>> point here: the stack exchange people were trying to negociate having the 
>> clear and free version of WMD for their own use, maybe showdown is actually
>> what came out of this and what allows Stack exchange to do their thing...
>> 
>> And besides: the point here is that we *can't actually use WMD safely*, but
>> we **can use pagedown safely!**.
>> 
>> I tried the plugin: it works, and it works well. It's also fairly trivial to
>> install the upstream showdown library, which is not shipped with the plugin
>> (which alleviates all possible copyright problems). You can take test the 
>> plugin at <http://testwiki.anarc.at/>
>> 
>> There are only three issues I could find during testing:
>> 
>>  1. two previews are showed (the showdown one and the regular ikiwiki one),
>>     which can be confusing, but is still necessary because the showdown one 
>>     doesn't parse ikiwiki directives. 
>>  2. the wiki needs to be rebuilt when the plugin is first activated for the
>>     stylesheets to regenerate. new wikis are not affected, and this can be
>>     deployed massively on farms without user intervention.
>>  3. on large pages, the edit screen isn't in the first screen, so it's not 
>>     obvious we're editing the page, which is also a little confusing - we 
>>     would need an anchor in there... Update: a simple patch fixes that... 
>>     but in a rather crude way:
>>
>>  [[!format diff """
--- a/IkiWiki/Render.pm
+++ b/IkiWiki/Render.pm
@@ -87,7 +87,7 @@ sub genpage ($$) {
        my $actions=0;
        if (length $config{cgiurl}) {
                if (IkiWiki->can("cgi_editpage")) {
-                       $template->param(editurl => cgiurl(do => "edit", page => $page));
+                       $template->param(editurl => cgiurl(do => "edit", page => $page) . '#editcontent');
                        $actions++;
                }
        }
"""]]
>>      ideally, we would show the edit box next to the page preview... And there's a way to do that too! But it requires some more CSS hackery, like [this](http://css-tricks.com/scrollfollow-sidebar/), for example:
>>
>>     #wmd-preview {
>>       position: relative;
>>       margin: 15px auto;
>>       float: left;
>>       width: 50%;
>>     }
>>     form {
>>       position: fixed;
>>       margin-left: 50%;
>>     }
>>
>> But this is getting a little crazy and I need to sleep now.
>>
>> [[!template id=gitbranch branch=anarcat/pagedown author="[[anarcat]]"]]
>>
>> Anyways, let's work on merging that pretty branch already shall we? :) --[[anarcat]]