Make the Automatic detection of "Enable touch events" work in Linux

Make the Automatic detection of "Enable touch events" work in Linux

Currently the automatic option of "Enable touch events" flag cannot
send the touch events to the pages, because the touch screen for
Linux is considered as an attach-slave device, the render thread sets
the "touchEnable" to false in this case. We now take consider both
floating-salve device and attach-slave device in order to send the
touch events to render.

BUG=443667
Committed: https://crrev.com/2746693b039b5c9176d13f4f8baeb39222538daf
Cr-Commit-Position: refs/heads/master@{#317353}

[lanwei, 2015-02-12 17:20:53]

lanwei@chromium.org changed reviewers:
+ rbyers@chromium.org, sadrul@chromium.org, tdresser@chromium.org

[lanwei, 2015-02-12 18:57:55]

On 2015/02/12 18:55:41, lanwei wrote:

sadrul@, I checked that it only sends out touch events if it has the
preventDefault on the touch event handler, no mouse event is sent out.

[tdresser, 2015-02-12 19:04:03]

On 2015/02/12 18:55:41, lanwei wrote:

I don't have enough context here to provide a useful review.

Stylistically, I prefer using {} when the condition of an if statement is
multi-line.

[Rick Byers, 2015-02-13 08:27:56]

On 2015/02/12 19:04:03, tdresser wrote:
> On 2015/02/12 18:55:41, lanwei wrote:
> 
> I don't have enough context here to provide a useful review.

Perhaps Sadrul or Yufeng is the right reviewer for this?  There's a bunch of
context here that they probably know best.

[sadrul, 2015-02-13 08:59:26]

On 2015/02/12 18:57:55, lanwei wrote:
> On 2015/02/12 18:55:41, lanwei wrote:
> 
> sadrul@, I checked that it only sends out touch events if it has the
> preventDefault on the touch event handler, no mouse event is sent out.

preventDefault() should not affect whether X11 sends us mouse-events for the
touchscreen or not. Do you see a difference in the stream of events we receive
in chrome from X11 when the JS does preventDefault() vs when it doesn't?

Also, how does this affect the cursor visibility? On ChromeOS, we hide the
cursor when we start receiving touch events. Does that work correctly for slave
devices? (I ask since touching a 'floating' touchscreen does not have an effect
on the system cursor, but touching an 'attached slave' touchscreen also moves
the cursor with the touch-point, and so I expect that to generate some mouse
events, and interfere with the cursor-visibility related code we have in chrome)

[lanwei, 2015-02-13 20:02:30]

On 2015/02/13 08:59:26, sadrul wrote:
> On 2015/02/12 18:57:55, lanwei wrote:
> > On 2015/02/12 18:55:41, lanwei wrote:
> > 
> > sadrul@, I checked that it only sends out touch events if it has the
> > preventDefault on the touch event handler, no mouse event is sent out.
> 
> preventDefault() should not affect whether X11 sends us mouse-events for the
> touchscreen or not. Do you see a difference in the stream of events we receive
> in chrome from X11 when the JS does preventDefault() vs when it doesn't?
> 
> Also, how does this affect the cursor visibility? On ChromeOS, we hide the
> cursor when we start receiving touch events. Does that work correctly for
slave
> devices? (I ask since touching a 'floating' touchscreen does not have an
effect
> on the system cursor, but touching an 'attached slave' touchscreen also moves
> the cursor with the touch-point, and so I expect that to generate some mouse
> events, and interfere with the cursor-visibility related code we have in
chrome)

I should be clearer about what I mean by preventDefault(). I mean that if we
have the
preventDefault(), the render will only receive touch events, otherwise, it will
receive
both touch events and gesture events which will simulate mouse events which can
be handled
if the page has mouse events. I am using Rick's eventTest page. 
http://rbyers.github.io/eventTest.html
If we have touch event and mouse event handles and if we preventDefault on touch
events, we
will only see touch events, no mouse event. If we do no have preventDefault on
touch events,
we will see both touch and mouse events, but the mouse events are not from
XEvent, it is from
the gesture event.

I checked that X11 does not send out any mouse event, only touch events, so it
is 
the same for both floating device and attaching device. The mouse events we saw
when
the flag is set to automatic is because the render does not consume the touch
events
and simulate mouse events from the gesture events.

I checked the attached-slave touch screen, it does not affect the cursor
visibility,
I did not see the cursor when I touch the pages.

[sadrul, 2015-02-19 17:18:14]

(whoops. Lost track of this. please feel free to ping me earlier)

On 2015/02/13 20:02:30, lanwei wrote:
> On 2015/02/13 08:59:26, sadrul wrote:
> > On 2015/02/12 18:57:55, lanwei wrote:
> > > On 2015/02/12 18:55:41, lanwei wrote:
> > > 
> > > sadrul@, I checked that it only sends out touch events if it has the
> > > preventDefault on the touch event handler, no mouse event is sent out.
> > 
> > preventDefault() should not affect whether X11 sends us mouse-events for the
> > touchscreen or not. Do you see a difference in the stream of events we
receive
> > in chrome from X11 when the JS does preventDefault() vs when it doesn't?
> > 
> > Also, how does this affect the cursor visibility? On ChromeOS, we hide the
> > cursor when we start receiving touch events. Does that work correctly for
> slave
> > devices? (I ask since touching a 'floating' touchscreen does not have an
> effect
> > on the system cursor, but touching an 'attached slave' touchscreen also
moves
> > the cursor with the touch-point, and so I expect that to generate some mouse
> > events, and interfere with the cursor-visibility related code we have in
> chrome)
> 
> I should be clearer about what I mean by preventDefault(). I mean that if we
> have the
> preventDefault(), the render will only receive touch events, otherwise, it
will
> receive
> both touch events and gesture events which will simulate mouse events which
can
> be handled
> if the page has mouse events. I am using Rick's eventTest page. 
> http://rbyers.github.io/eventTest.html
> If we have touch event and mouse event handles and if we preventDefault on
touch
> events, we
> will only see touch events, no mouse event. If we do no have preventDefault on
> touch events,
> we will see both touch and mouse events, but the mouse events are not from
> XEvent, it is from
> the gesture event.
> 
> I checked that X11 does not send out any mouse event, only touch events, so it
> is 
> the same for both floating device and attaching device. The mouse events we
saw
> when
> the flag is set to automatic is because the render does not consume the touch
> events
> and simulate mouse events from the gesture events.
> 
> I checked the attached-slave touch screen, it does not affect the cursor
> visibility,
> I did not see the cursor when I touch the pages.

I noticed that X11 does send some motion events when interacting with an
attached-slave touchscreen. But looks like we already filter out events with
XIPointerEmulated flags. That's probably why it doesn't cause any issues.

Unfortunately, TouchFactory also maintains a list of touchscreen devices, and we
use that information in a few places. We should get rid of that from
TouchFactory though (crbug.com/460068), and always get the necessary info from
DeviceDataManager. So this change looks good.

LGTM

[lanwei, 2015-02-20 18:22:11]

The CQ bit was checked by lanwei@chromium.org

[commit-bot: I haz the power, 2015-02-20 18:23:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/914393002/1

[commit-bot: I haz the power, 2015-02-20 18:31:23]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-20 18:32:26]

Patchset 1 (id:??) landed as
https://crrev.com/2746693b039b5c9176d13f4f8baeb39222538daf
Cr-Commit-Position: refs/heads/master@{#317353}