external plugin in your favorite programming language. Wow us at how much
easier you can do the same thing in your favorite language. ;-)
+There's now a second external plugin, the [[rst]] plugin, written in
+python. It uses a `proxy.py`, a helper library for ikiwiki python plugins.
+
[[toc ]]
## How external plugins use XML RPC
call `getvar("config", "url")`. To set it, call
`setvar("config", "url", "http://example.com/)`.
+The `%pagestate` is a special hash with a more complex format. To access
+it, external plugins can use the `getstate` and `setstate` RPCs. To access
+stored state, call `getstate("page", "id", "key")`, and to store state,
+call `setstate("page", "id", "key", "value")`.
+
+To access ikiwiki's ARGV array, call `getargv()`. To change its ARGV, call
+`setargv(array)`.
+
## Notes on function parameters
The [[plugin_interface_documentation|write]] talks about functions that take
to convert these named parameters into something more natural for the
language as part of their XML RPC interface.
+## undef
+
+XML RPC has a limitation that it does not have a way to pass
+undef/NULL/None. There is an extension to the protocol that supports this,
+but it is not yet available in the [[cpan XML::RPC]] library used by
+ikiwiki.
+
+Until the extension is available, ikiwiki allows undef to be communicated
+over XML RPC by passing a sentinal value, a hash with a single key "null"
+with a value of an empty string. External plugins that need to communicate
+null values to or from ikiwiki will have to translate between undef and
+the sentinal.
+
## Function injection
Some parts of ikiwiki are extensible by adding functions. For example, the
Since XML RPC can't pass around references to objects, it can't be used
with functions that take or return such references. That means you can't
-use XML RPC for `cgi` or `formbuilder` hooks (which are passed CGI and
+100% use XML RPC for `cgi` or `formbuilder` hooks (which are passed CGI and
FormBuilder perl objects), or use it to call `template()` (which returns a
perl HTML::Template object).
-Also. the `getopt` hook doesn't work, as ARGV is not available to the external
-plugin.
-
## Performance issues
Since each external plugin is a separate process, when ikiwiki is
Injecting a replacement for a commonly called ikiwiki function
could result in a lot more RPC calls than expected and slow
eveything down. `pagetitle`, for instance, is called about 100 times
-per page build. Memoizing injected functions whenever possible is a very
-good idea.
+per page build. Whenever possible, you should tell ikiwiki to memoize
+injected functions.
In general, use common sense, and your external plugin will probably
perform ok.