Vehicle Information Access API EventHandlers Proposal

Hi All,

After discussions with the Generic Sensor API Working Group at the TPAC
last week we have proposed a refactoring of the data access methods in the
Vehicle Information Access API to utilise EventHandlers instead of the
current pub/sub model.

This proposal is with the intention to make the API more usable and
intuitive to a web developer, so I would be interested to hear your
opinions on the potential change.

Current Vehicle Information Access API using pub/sub -
http://rawgit.com/w3c/automotive/master/vehicle_data/vehicle_spec.html
GitHub Proposal using EventHandlers -
https://github.com/w3c/automotive/issues/72

Tobie Langel from the Generic Sensor API WG has commented proposing a
number of potential implementations, which I have copied below.

The existing API also does not allow for subscriptions to individual
attributes within an interface, also detailed in the GitHub discussion, so
this technique will also allow for such an implementation.

I look forward to hearing your opinions.

Kind regards,

Adam


   1.

   Creating dedicated event handlers for each properties:

   interface VehicleSignal : Vehicle {
     Promise set (object value);
     attribute EventHandler onerror;
     attribute Zone? zone;
   };
   interface Trip : VehicleSignal {
     attribute EventHandler ondistancechange;
     attribute EventHandler onaveragespeedchange;
     attribute EventHandler onfuelconsumptionchange;
   };

   Which would let you write code like:

   vehicle.trip.onaveragespeedchange = function(e) {
       // do stuff.
   };

   2.

   creating dedicated generic observers:

   [Constructor(DOMString type, Zone zone),
Exposed=(Window,Worker)]interface VehicleSignal : Vehicle {
     Promise set (object value);
     attribute EventHandler ondata;
     attribute EventHandler onchange;
     attribute EventHandler onerror;
     attribute DOMString type; // or Enum
     attribute Zone zone;
   };
   interface Trip {
     attribute VehicleSignal distance;
     attribute VehicleSignal averageSpeed;
     attribute VehicleSignal fuelConsumption;
   };

   Which would let you write code like:

   vehicle.trip.averageSpeed.onchange = function(e) {
       // do stuff.
   };

   3.

   creating dedicated specific observers:

   [Constructor(Zone zone), Exposed=(Window,Worker)]interface
VehicleSignal : Vehicle {
     attribute EventHandler onerror;
     attribute Zone zone;
   };
   interface VehicleDistanceSignal : VehicleSignal {
     // specific stuff
   };
   interface VehicleAverageSpeedSignal : VehicleSignal {
     // specific stuff
     EventHandler onaveragespeedchange
   };
   interface VehicleFuelConsumptionSignal : VehicleSignal {
     // specific stuff
   };
   interface Trip {
     attribute VehicleDistanceSignal distance;
     attribute VehicleAverageSpeedSignal averageSpeed;
     attribute VehicleFuelConsumptionSignal fuelConsumption;
   };

   Which would let you write code like:

   vehicle.trip.averageSpeed.onaveragespeedchange = function(e) {
       // do stuff.
   };


I believe that the last solution is what you'll end up ultimately
gravitating towards. The generalizations you're trying to make to go for
solution 2 will end up creating lots of edge cases you'll have to handle in
prose and will create a poor overall developer experience. Solution 1 could
be an interesting proposal, but I'm concerned it will make for an overall
more complex and less flexible spec.
-- 
*Adam C*rofts *MEng (Hons) MIET*
Connected Infotainment
Electrical Engineering
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