如何有意义地检测低规格的移动设备？

Question

Right now I only know about Scientiamobile's WURFL and a few others. Those libraries or databases tell you quite a lot of things about the device but none of them can clearly indicate that you shouldn't use CSS transitions or other sorts of animation because even if the device supports it, its a complete different story that those features will run smoothly and this is my major concern when building mobile web apps.

Is it technically possible to 'classify' devices in this direction, using the 'WURF' database ? And which device capabilities I should use to 'group' devices as 'fast' in terms of graphic power ?

Finally, I just need a rating of the device from 1-5 in order to decide which gfx operations I can use.

well, any thought is welcome. It turns out as real brainer and the researches on internet didn't bring up anything useful except lots of data about device caps.

Update-1 : I just got a response from ScientiaMobile : "we have been playing around with the idea of some form of Javascript performance index (possibly based on one of the existing benchmarks) that could give some indication of that, but we are still not there yet. The problem is complex."

Update-2 : The biggest bottlenecks we discovered in mobile web apps

1. animation power
2. PNG transparency
3. text and box shadows
4. image resizing

For us its really enough to figure out that we need to disable those features as they can bring any application to its knees. Possibly, there are also other approaches.

Thank you.

Answer 1

Unfortunately, I do not believe this is possible today for the general case.

If you are only interested in a limited number of devices, of course you could test each and target those specifically via user agent or JavaScript-based detection.

Within the context of a thick app (eg, you "wrap" your web site with something like Apache Cordova ), it would be possible to provide JavaScript access to some of the device internals (eg, amount of total memory, amount of free memory, processor speed), but otherwise, this information is not available from the browser. As you've hinted at, having access to this type of device information may still be insufficient (eg, seemingly "high spec" devices that perform poorly).

JavaScript feature detection libraries like Modernizr can answer whether something such as box-shadow and text-shadow is supported by the user's current browser, but does not provide information about how well or how quickly supported features will be rendered.

Likewise, the datasets from Browserscope and related project ringmark (somewhat of a JavaScript analog to WURFL) answer these browser support questions on a per-browser-version basis through crowdsourced benchmarking tests (eg, does the iPhone support CSS3 transitions?), and for the general case, this is what would be necessary. You would need to run a benchmark test for the various features in question and assess real-time performance. However, even this has its limitations:

• Because the necessary conditions for speed (available memory, processor, battery, network connection, etc.) are constantly in flux as mobile users move around, receive calls, change hardware settings, launch background applications, etc., the result of the benchmark is likely to be unreliable/unrepeatable.
• Benchmarking takes time and will invariable add a (hopefully unnoticable) delay.
• Depending on the feature, benchmarking may not be practical.
• Features may behave differently in combination (eg, animating transparent PNGs with shadows) or at scale (eg, every image on the page is animating) than individually in the benchmarking test.
• If you rely on benchmarking datasets instead of performing your own real-time benchmarking, the sample size, scope, and age of the dataset greatly limits its usefulness.

A final point is that I haven't even addressed is the fact that performance is rather subjective . Say it were somehow possible to assess/predict the speed of an animation. If the animation will run at 15 fps, should the user see that animation? What about 5 fps? Who gets to be the ultimate arbiter that decides the threshold for whether or not a given feature performs well enough ?

The best advice I can offer today is to reduce (or eliminate) your reliance on the troublesome features for the time being. It may seem terrible to suggest going back to "the old way" of using images with precomposed shadows or making background gradients without CSS3, but at the end of the day the user experience should take precedence over using the shiney new technology. Many mobile devices are simply not there yet, and neither are the detection methods. If you must use these features, perhaps consider a simple but unobtrusive way for users to opt-in/opt-out like Gmail's "standard" vs. "basic HTML" view options, or consider automatically doing the opt-in for known good browsers.

Answer 2

I can't add much more than 'user113215' already said. Also its not an answer to the actual question but rather to the actual problem :

I did experiment with a few users and we were using a simple welcome popup menu, asking the user to turn off special effects such shadows and animations. The most of the test users did appreciate the choice and clearly understood the means of such menu. We do integrate this now more advanced and in conjunction with a hidden benchmark for auto pre-selection of GFX effects.

Thank you. g

Answer 3

In short, no. How we define the smoothness of animations and graphics is solely depend on the FPS(frame-per-second). And in this question we are talking about "web-app"s, which are making use of HTML and JS on the client-side. Since none of the client side provide interface for the programs to get the FPS by HTML or JS, it is impossible to tell if the client is smooth or not.

However, if you really want a benchmark on the performance of web-app. You can make use of stats.js to monitor the change of stat and have a benchmark for you to suggest your client activating or disabling any sort of effects on runtime. This method even working with most FXs of Javascript libraries like jquery too. But this will take sometime for you to get enough data before applying changes and the stat may differ from the status of the device, such as memory usage, concurrent applications, etc.