Highlighter Hooks -- How?

[darth-cheney]

Based on the other open issues posted here, it seems like everyone would benefit from more hooks.

In my case, it would be good to have hooks that fire throughout the highlighting process. I'm willing to implement a few of these and PR, but it's unclear to me based on reading the other code how one would implement a new hook within the highlighter.js module (ie, access the greater annotator app to runHook).

Is there a simplified explanation of the adding hooks process (not from the docs) or can someone provide one?

[tilgovi]

The App instance has the runHook method. All you need to do to add hooks is change the code to run a hook with a new name.

Here's the definition of runHook: https://github.com/openannotation/annotator/blob/master/src/app.js#L112

However, we try to keep the modules plain JS modules that can be used without an Annotator App. Eventually, we may split some of these out into their own repositories so various community members can take responsibility for them independently.

The way to do this is to make the Highlighter class have new options for callbacks. The instance calls the callbacks, which are simple functions rather than "hooks".

Then, the Highlighter extension module can listen to the start hook and capture the app argument on behalf of its surrounding closure context and the instantiation of the Highlighter instance in line 215 can extend its options with default callback functions that invoke app.runHook().

Here's the start hook documentation, which just shows that it receives the app instance: http://docs.annotatorjs.org/en/latest/module-development.html#module-hooks

Here's the place where you could add a start hook handler to the highlighter, when it's loaded as an extension module: https://github.com/openannotation/annotator/blob/master/src/ui/highlighter.js#L212

Let me know if that helps.