On Sat, Jan 31, 2009 at 6:45 PM, Brent Yorgey
On Sat, Jan 31, 2009 at 06:23:29PM -0500, Braden Shepherdson wrote:
Brent Yorgey wrote:
I am very pleased to announce the 0.2 release of the diagrams package,
Would this make a handy plugin for gitit? I'm currently putting diagrams together in xfig and saving them to my gitit tree while taking notes in gitit, but being able to write diagrams code into gitit would be great.
How easy or hard would this be to accomplish?
Well, the short answer is: I think diagrams would be very well-suited to this, and the difficulty probably depends more on gitit than diagrams. Perhaps someone who knows more about gitit can speak to this as well.
/me looks around. oh.
In theory, it should be easy to write a plugin which takes some Haskell code defining a top-level binding 'dia' (or something similar) of type Diagram, wraps it in some appropriate imports and an appropriate one-line definition for main, then compiles and runs it in a sandbox and sticks the generated image in the wiki output. The devil's in the details, of course: you'd probably want to cache the generated images indexed by a hash of the diagrams code that generated them, to avoid recomputing the image every time the page loads. And there are probably other considerations I'm not thinking of.
-Brent
As it happens, I recently got interested in plugins for Gitit/Pandoc since they're the most straightforward way to implement features I would like very much*. John discussed it briefly: http://groups.google.com/group/pandoc-discuss/browse_thread/thread/54272f922... The crucial part is the definition processWith & processWithM: processWith :: (Data a, Data b) => (a -> a) -> b -> b processWithM :: (Monad m, Data a, Data b) => (a -> m a) -> b -> m b If I understand Braden, he wants to write down some Haskell expression and see instead whatever image is generated. So suppose we have syntax like this: !!!! Basic Circle draw $ circle 50 10 !!!! We toss into gitit a call to 'processWith imageGenerator'. imageGenerator looks something like imageGenerator a = unsafePerformIO $ do expr <- filterPlugins a img <- Diagrams.run expr writeFile path img replace a ("![](" ++ path ++ ")") where path = "static/user/" ++ "Basic Circle.png" Obviously this is just pseudocode, as 'replace' and 'filterPlugins' are nontrivial to write, but you get the idea. We stream through the wikitext looking for our special symbols which denote Diagram code, then we pass it to Diagrams (I handwave over how to turn String into a function suitable for Diagrams - maybe this would be actually a call to a Diagram executable?), save the image to a known location, and then replace the Diagram code with the Markdown syntax for linking/including an image. I doubt I'll do this anytime soon, but I suspect that with this approach, such a plugin would be about an evening's work or so. * signatures, interwiki links, and possibly categories -- gwern