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Re: IE implementation of navigator.maxTouchPoints

From: Rick Byers <rbyers@chromium.org>
Date: Thu, 11 Sep 2014 14:31:23 -0400
Message-ID: <CAFUtAY-tSH_6Re3gvq-5dfzchynmCQ58WZ4XG0P__2AzgOYC7w@mail.gmail.com>
To: Sangwhan Moon <smoon@opera.com>
Cc: Jacob Rossi <Jacob.Rossi@microsoft.com>, "public-pointer-events@w3.org" <public-pointer-events@w3.org>, David Bokan <bokan@chromium.org>
Essentially yes (although I don't think that compiles - you mean
IsTouchDevicePresent, not IsTouchEnabledDevice?).  I believe bokan@ plans
to land something like this ASAP.

Thanks,
   Rick


On Thu, Sep 11, 2014 at 1:29 AM, Sangwhan Moon <smoon@opera.com> wrote:

> 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
>
Received on Thursday, 11 September 2014 18:32:12 UTC

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