Thursday, February 12, 2009

Trouble extending Trac navigation.

I'm in the process of building a new Trac site. I wanted to add new menu items to the main navigation. Hiding or rearranging the default menu items in Trac 0.11 is quite straightforward. It can all be done in the Trac configuration. However, new menu items need to be part of a component. Hence, the need for the NavAdd plugin.

It looks like the plugin has not yet been updated to fit the 0.11 plugin architecture, although it does work with 0.11. The Trac plugin API changes weren't too drastic. I did notice some strange behaviour though. It turns out that any menu items added with the NavAdd plugin can not be considered active.

What? No active menu items? Well, it isn't really the NavAdd plugins' fault. It turns out, that in order to have an active menu item, the current request needs to be handled by the same component that produces the menu item. I discovered this by looking at the timeline Trac component. This component actually implements the IRequestHandler interface. This is necessary because the timeline component handles requests to the /timeline URI. The menu item produced by this component becomes active anytime the /timeline URI is visited.

So, this design works well for components that have URIs. But what if I want to add menu items that point to wiki pages? And what if I want to have my menu item become active when visiting those pages? There is currently no way to do this. My suggestion would be that the INavigationContributor interface adds a new uri field to be returned from get_navigation_items(). When page corresponding to this uri becomes active, so does the custom menu item.