Rabu, 22 Februari 2012

Everything you wanted to know about HTML5 in the car, Part II

Welcome to the second installment in my Q&A series on HTML5 in the car. Last week, we looked at CSS, cross-platform execution, and asynchronous design. This week, we turn our attention to web servers, native plug-ins, instrument clusters, and display updates.

If I don’t use a web server in my infotainment system, will I miss out on some features of HTML5?
A web server isn’t strictly necessary, but there are two very good reasons for including one. First, it lets you export a user interface to devices outside the car, thereby allowing mobile phones or tablets to run apps that are hosted on the vehicle head unit. Second, it lets you export internal car resources, as a URL, to HMI software running in the head unit. For instance, the web server could provide the HMI with access to static vehicle-configuration data (through an xml file) or to a back-up camera (through a video stream).

Will using native code plug-ins compromise my ability to leverage HTML5?
This is tricky, because a lot of things you want to do may require native code. So, yes, use native code, but do it judiciously. The more native code you use, the more it will limit the cross-platform capability of the HTML5 code that relies on it. The good news is that with HTML5 gaining so much functionality, plug-ins are needed far less than ever before.

A sample climate control app from the
QNX CAR 2 platform, created with HTML5.
Would you consider HTML5 as an option for cluster instruments: speedometers, tachometers, etc.?
At this point, I’d say no. HTML5 makes a lot of sense for in-vehicle infotainment, but it doesn’t provide the response needed for a vehicle cluster and it won't ensure safety-critical certification. Plus, the instrument cluster isn’t where you realize a lot of HTML5’s value: downloadable apps, connectivity to mobile devices, and so on. If the cluster and the infotainment system eventually merge into one big screen, then it’s more likely you could use HTML5 for both — but that’s still a few years out.

What’s a good way to get responsive display updates (10Hz update) into HTML5? Websockets?
If you need to deliver high-speed updates to your head unit, Websockets is one way to go. Make sure, however, that you don’t stall the rest of the JavaScript engine while your main thread is blocked on tasks. If you create another thread to monitor for changes, you can do it just as effectively (and probably with less work) with a JNEXT or NPAPI call into native code.

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