Scaling scroll/fling events in multi-monitor setup

Scaling scroll/fling events in multi-monitor setup

The CL adds an event filter that transforms input event properties
in the extended desktop environment. It currently scales scroll/fling
events' offset values based on the following logic:

1. Linear scaling w.r.t. the device scale factor, which is 2x for
   highDPI displays.
2. 1.2x scaling for external displays, since they are usually larger
   than internal ones.

Both scalings can stack on each other, i.e. you can get as high as
a 2.4x boost if you have a high DPI external display.

Contributed by sheckylin@chromium.org

BUG=chromium:166392
TEST=Tested on link w/o external display.

Change-Id: Ie29e03fcf9f6e5ae1dd6231990103237c3129fd6


Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=176038

[Shecky Lin, 2013-01-03 09:18:43]

Please take a look of this, thanks!

[DaveMoore, 2013-01-07 04:31:45]

LGTM modulo nit

https://codereview.chromium.org/11743013/diff/6001/ui/base/events/event.h
File ui/base/events/event.h (right):

https://codereview.chromium.org/11743013/diff/6001/ui/base/events/event.h#new...
ui/base/events/event.h:638: void Rescale(const float factor);
Nit: The naming of this is a bit strange. Isn't it "Scale" not "Rescale"?

[Shecky Lin, 2013-01-07 04:36:55]

On 2013/01/07 04:31:45, DaveMoore wrote:
> LGTM modulo nit
> 
> https://codereview.chromium.org/11743013/diff/6001/ui/base/events/event.h
> File ui/base/events/event.h (right):
> 
>
https://codereview.chromium.org/11743013/diff/6001/ui/base/events/event.h#new...
> ui/base/events/event.h:638: void Rescale(const float factor);
> Nit: The naming of this is a bit strange. Isn't it "Scale" not "Rescale"?

Agreed. There was no "Scale" done in the first place.

[Ben Goodger (Google), 2013-01-07 18:06:05]

https://codereview.chromium.org/11743013/diff/13001/ash/display/event_transfo...
File ash/display/event_transformation_filter.cc (right):

https://codereview.chromium.org/11743013/diff/13001/ash/display/event_transfo...
ash/display/event_transformation_filter.cc:39: float scale = 1.0f;
delete

https://codereview.chromium.org/11743013/diff/13001/ash/display/event_transfo...
ash/display/event_transformation_filter.cc:43: scale *= scale_at_target;
float scale = scale_at_target;

https://codereview.chromium.org/11743013/diff/13001/ash/display/event_transfo...
File ash/display/event_transformation_filter.h (right):

https://codereview.chromium.org/11743013/diff/13001/ash/display/event_transfo...
ash/display/event_transformation_filter.h:18: class ASH_EXPORT
EventTransformationFilter : public ui::EventHandler {
Replace all uses of the "filter" terminology (now deprecated) with "handler"

https://codereview.chromium.org/11743013/diff/13001/ash/shell.cc
File ash/shell.cc (right):

https://codereview.chromium.org/11743013/diff/13001/ash/shell.cc#newcode473
ash/shell.cc:473: event_transformation_filter_.reset(new
internal::EventTransformationFilter());
nit: remove ()

https://codereview.chromium.org/11743013/diff/13001/ash/shell.h
File ash/shell.h (right):

https://codereview.chromium.org/11743013/diff/13001/ash/shell.h#newcode322
ash/shell.h:322: return event_transformation_filter_.get();
nit: outdent 2

[Shecky Lin, 2013-01-09 07:53:25]

On 2013/01/07 18:06:05, Ben Goodger (Google) wrote:
>
https://codereview.chromium.org/11743013/diff/13001/ash/display/event_transfo...
> File ash/display/event_transformation_filter.cc (right):
> 
>
https://codereview.chromium.org/11743013/diff/13001/ash/display/event_transfo...
> ash/display/event_transformation_filter.cc:39: float scale = 1.0f;
> delete
> 
>
https://codereview.chromium.org/11743013/diff/13001/ash/display/event_transfo...
> ash/display/event_transformation_filter.cc:43: scale *= scale_at_target;
> float scale = scale_at_target;
> 
>
https://codereview.chromium.org/11743013/diff/13001/ash/display/event_transfo...
> File ash/display/event_transformation_filter.h (right):
> 
>
https://codereview.chromium.org/11743013/diff/13001/ash/display/event_transfo...
> ash/display/event_transformation_filter.h:18: class ASH_EXPORT
> EventTransformationFilter : public ui::EventHandler {
> Replace all uses of the "filter" terminology (now deprecated) with "handler"
> 
> https://codereview.chromium.org/11743013/diff/13001/ash/shell.cc
> File ash/shell.cc (right):
> 
> https://codereview.chromium.org/11743013/diff/13001/ash/shell.cc#newcode473
> ash/shell.cc:473: event_transformation_filter_.reset(new
> internal::EventTransformationFilter());
> nit: remove ()
> 
> https://codereview.chromium.org/11743013/diff/13001/ash/shell.h
> File ash/shell.h (right):
> 
> https://codereview.chromium.org/11743013/diff/13001/ash/shell.h#newcode322
> ash/shell.h:322: return event_transformation_filter_.get();
> nit: outdent 2

Done!

[Ben Goodger (Google), 2013-01-09 17:23:34]

lgtm

[commit-bot: I haz the power, 2013-01-10 04:28:11]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/sheckylin@chromium.org/11743013/20001

[commit-bot: I haz the power, 2013-01-10 06:49:15]

Change committed as 176038