ikiwiki/doc/todo/Post-compilation_inclusion_of_the_sidebar.mdwn

In some sites (mine, for example), the pages are quasi-static, while the sidebar must be updated at each commit
(because it contains some lists, like "last posts" or "last updates", or a tagcloud). As this sidebar is included
in every page of the site, many commits can potentialy leat to a full re-compilation....

I think a sidebar included after the compilation (via a SSI mechanism for example) would make sense and 
reduce the dependencies.

Different things could be possible:

* output as .shtml instead of .html
* ignore the sidebar->page dependency links
* consider the *real* dependencies; pageA may include the title (only) of pageB, but don't need to be recompiled 
after each typo correction on pageB.

shtml output with open cgi web access is a potential security hole and can DoS the site, but it's not a problem for a 
single-editor site.

NicolasLimare

> This is a good idea, though sadly not portable enough to be the default.
> Especially if the only way to do it is with .shtml.
> But I really like the idea of not rebuilding the sidebar all the time. 
> Definitly a TODO, for me, if I can figure out how to do it. Patches
> eagerly accepted. 
> 
> I have implemented a htmlext configuration item, that lets you control
> what extension ikiwiki uses for output html pages. So in theory, a
> sidebar could be done as you describe using .shtml. --[[Joey]]

[[wishlist]]

> I have a plan for a way to avoid unecessary rebuilds caused by the
> sidebar. The idea is to use wikistate to store what a sidebar renders to.
> Then in the needsbuild hook, render sidebar(s) and compare with their
> previous stored rendering. If a sidebar's rendered content has changed,
> then all pages that display that sidebar need to be forced to be rebuilt.
> 
> Also, if there is no previous stored rendering for a sidebar, or
> if there is a stored rendering for a sidebar page that no longer exists, then
> the pages need to be rebuilt. (This should deal with the [[bugs/Building_a_sidebar_does_not_regenerate_the_subpages]] bug.
> 
> This would also save significant time, since the stored sidebar rendering
> could just be dumped into the page by the pagetemplate hook. Current code
> re-loads and renders the same sidebar file for every page built!
> 
> The sticky part is (relative) links on the sidebar. These would need to
> be modified somehow depending on the page that the sidebar is placed on,
> to not break the link.
> 
> Another wrinkle is changing subpage links on a sidebar. Suppose a sidebar
> links to page `foo`. If page `bar/foo` exists, the sidebar on page bar will, 
> currently, link to that page, in preference to a toplevel `foo`.
> If `bar/foo` is removed, it will update to link to `foo`. With the new
> scheme, the stored sidebar rendering is not for page `foo`, and so
> the change of the `bar/foo` link will not be noticed or acted on.
> Granted, it's unlikely that anyone relies on the current behavior. You
> generally want links on a sidebar to link to the same place on every page
> that displays it. So finding some way to force all links on a sidebar to 
> be handled absolutely and documenting that would avoid this problem.
>
> So, one way to handle both the above problems would be to use the
> pre-rendered sidebar for each page, but use a html parser to look for
> links in it, and munge them to work as relative links on the page the
> sidebar is being added to. Or, if the wiki's url is known, just do this
> once when rendering the sidebar, adding the full url to the links.
> (Maybe require `url` be set when using sidebar?)
> --[[Joey]]