Replace ve.trackRegisterHandler with two methods: ve.trackSubscribe and
ve.trackSubscribeAll. The former takes an additional string argument 'topic',
which specifies a string prefix on which to match event names. The callback is
only called on matching events. The latter, ve.trackSubscribeAll, binds a
handler to all track events, regardless of topic.
This patch simplifies argument-handling by eliminating variadic ve.track calls
in favor of a single object that encodes all event data. The loose coupling of
track event emitters and subscribers makes relying on unnamed positional
argument conventions brittle; property access works better.
Change-Id: I3b58ce0f48ad3c9b56fcaa9c2226cc79bbcd4051
This patch adds ve.track; it provides a means for VisualEditor code to log
various changes of state that are of potential analytic interest. This is done
without coupling VisualEditor to a particular analytics framework by providing
a method, ve.hook.registerHandler, by which event data may be routed to a
particular analytic framework for processing and dispatch.
ve.track uses a $.Callbacks-like object for tracking analytic events which can
remember an arbitrary number of past events. This is done by maintaining an
array containing the arguments of past calls and maintaining a counter for each
callback indicating its position in the queue (i.e., how many events it has
already received.) This ensures handlers are called for each event, including
events which were fired before the handler was registered. This allows the
load-order of VE and analytics components to remain unspecified.
Change-Id: I29740fa7a0ac403e484e0acee6dfcadaf6fc4566
