Re: IE implementation of navigator.maxTouchPoints

Makes sense, is was this what you had in mind?

https://gist.github.com/cynthia/fe95daed5322109f567c

(I didn't actually check if this compiles, my work environment is 100%
*nix. :-()

Cheers,
Sangwhan

On Thu, Sep 11, 2014 at 10:46 AM, Rick Byers <rbyers@chromium.org> wrote:

> Thank you!  Indeed it looks like this is Windows 7 only, and unlike IE we
> do still want to support touchscreens on Windows 7 (a small but non-trivial
> fraction of our touchscreen users are still on Windows 7).  It looks like SM_DIGITIZER
> is false in these cases, so I think we can try looking at SM_MAXIMUMTOUCHES
> only when SM_DIGITIZER is true. Sound reasonable to you?
>
> Thanks,
> Rick
>
>
> On Wed, Sep 10, 2014 at 7:44 PM, Jacob Rossi <Jacob.Rossi@microsoft.com>
> wrote:
>
>>  Definitely happy to help here. Our code is roughly:
>>
>>
>>
>> lMaxTouchPoints = 0;
>>
>> if (Win8+)
>>
>> {
>>
>>     lMaxTouchPoints = GetSystemMetrics(SM_MAXIMUMTOUCHES);
>>
>> }
>>
>> return lMaxTouchPoints;
>>
>>
>>
>> The OS check is there because we don’t support touch in the IE platform
>> on Windows 7 and usage of touchscreen devices on Win7 is extremely low
>> (most have moved to Win8+).
>>
>> Have you seen reports of this on Windows 8/8.1 or just Windows 7?
>>
>>
>>
>> There definitely are touchpad drivers that like to install a fake touch
>> driver in order to fake zoom gestures (e.g. pinch to zoom). I don’t think
>> there’s a way for the Windows input stack to tell the difference between
>> that and an actual touchscreen. But if you’d like, I can loop you in with
>> our Win32 input team.
>>
>>
>>
>> -Jacob
>>
>>
>>
>> *From:* rbyers@google.com [mailto:rbyers@google.com] *On Behalf Of *Rick
>> Byers
>> *Sent:* Wednesday, September 10, 2014 10:26 AM
>> *To:* Jacob Rossi
>> *Cc:* public-pointer-events@w3.org; David Bokan
>> *Subject:* IE implementation of navigator.maxTouchPoints
>>
>>
>>
>> Hey Jacob,
>>
>> We're getting reports of some complaints of navigator.maxTouchPoints
>> returning 1 on Chrome when there is in fact no touchscreen.  IE11 correctly
>> returns 0.  http://crbug.com/352942.  Scott (from MS OpenTech) wrote the
>> code
>> <https://code.google.com/p/chromium/codesearch#chromium/src/ui/base/touch/touch_device_win.cc&q=MAXTOUCHPOINTS&sq=package:chromium&type=cs&l=17>
>> for this for us, basically just:
>>
>>
>>
>> int MaxTouchPoints() {
>>
>>   return GetSystemMetrics(SM_MAXIMUMTOUCHES);
>>
>> }
>>
>>
>>
>> Apparently, despite what we'd expect fro the MSDN docs, this is
>> insufficient.  Users report that it returns 1 in scenarios with both an
>> internal and external mouse plugged in - although we haven't been able to
>> reproduce it (and they've confirmed they see those values from the API
>> directly, so it's not some bug in chrome).
>>
>>
>>
>> Any chance you can share the algorithm with us that IE uses to compute
>> maxTouchPoints on windows?  Ideally Chrome and IE would always agree here,
>> and there's obviously some special cases.
>>
>>
>>
>> Thanks,
>>
>>    Rick
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>


-- 
Sangwhan Moon [Opera Software ASA]
Software Engineer | Tokyo, Japan