DoubleTap Zoom support for Mobile Viewport pages

DoubleTap Zoom support for Mobile Viewport pages

In case of ForceEnableZoom, MobileVieport pages not
supporting doubleTapZoom.
So added patch to support it.

BUG=701796
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

[sujith, 2017-03-15 15:50:37]

sujiths.s@samsung.com changed reviewers:
+ johnme@chromium.org, rjkroege@chromium.org

[sujith, 2017-03-15 15:50:38]

PTAL

[johnme, 2017-03-15 17:05:15]

johnme@chromium.org changed reviewers:
+ bokan@chromium.org

[johnme, 2017-03-15 17:05:16]

+bokan, who owns zooming/viewports

What would double-tap zoom achieve on mobile (width=device-width) pages?

Desktop pages are usually composed of multiple narrower columns, so double-tap
zoom typically fits a column to the width of the screen, which works well (and
Text Autosizing usually ensures that the text in that column is readable when
the column is fit to the screen width).

But mobile pages almost always only have a single column of text (except perhaps
on tablets?), so double-tap zoom would mean having to pan sideways for every
line of text :-|

Additionally, the text on mobile pages should already be legible without
zooming.

Users who want things bigger for accessibility reasons should instead scale up
their entire display:
- on Android N+ use Settings > Display > "Display size";
- on Win 10 use Display Settings > "Change the size of
  text, apps and other items";
- on Retina macOS use System Preferences > Displays >
  Display > Resolution > Scaled;
- unfortunately there's no equivalent on iOS or on
  versions of Android prior to Nougat (it's only possible
  to scale text, not the whole display)

Those accessibility settings shrink the device-width and increase the
devicePixelRatio proportionately (so rendering remains crisp not blurry), thus
Chrome will render the webpage narrower but at higher density, and then the OS
will scale this up to fill the screen width, so that in the extreme case a
tablet user could use scaled up version of the phone version of a website
designed for 320dp wide devices.

User awareness of these modern ways of scaling your display isn't great yet
though - we should probably focus on raising awareness.

[bokan, 2017-03-15 18:26:24]

I generally agree with John that this probably isn't super useful. In principle
I do find it inconsistent that force zoom allows pinch-zoom but not double-tap
to zoom. IMO, the same arguments apply to pinch-zoom as to double-tap to zoom.

The one down side I see is that this would reinstate the 300ms click delay,
right? I would guess many users have "force zoom" on just to enable zoom on a
few specific sites. I think, on-balance, adding back the 300ms delay is probably
a worse outcome than enabling double-tap zoom in these niche cases.

[sujith, 2017-03-16 06:39:36]

On 2017/03/15 18:26:24, bokan wrote:
> I generally agree with John that this probably isn't super useful. In
principle
> I do find it inconsistent that force zoom allows pinch-zoom but not double-tap
> to zoom. IMO, the same arguments apply to pinch-zoom as to double-tap to zoom.
> 
> The one down side I see is that this would reinstate the 300ms click delay,
> right? I would guess many users have "force zoom" on just to enable zoom on a
> few specific sites. I think, on-balance, adding back the 300ms delay is
probably
> a worse outcome than enabling double-tap zoom in these niche cases.

@bokan,
yeah this patch will reinstate the 300ms click delay, if user enable force zoom.
I thought for force zoom, both double tap and pinch zoom should work,
that's why i raised this patch.

Could you please close the bug, i don't have permission to do it.

[bokan, 2017-03-16 12:07:34]

On 2017/03/16 06:39:36, sujith wrote:
> On 2017/03/15 18:26:24, bokan wrote:
> > I generally agree with John that this probably isn't super useful. In
> principle
> > I do find it inconsistent that force zoom allows pinch-zoom but not
double-tap
> > to zoom. IMO, the same arguments apply to pinch-zoom as to double-tap to
zoom.
> > 
> > The one down side I see is that this would reinstate the 300ms click delay,
> > right? I would guess many users have "force zoom" on just to enable zoom on
a
> > few specific sites. I think, on-balance, adding back the 300ms delay is
> probably
> > a worse outcome than enabling double-tap zoom in these niche cases.
> 
> @bokan,
> yeah this patch will reinstate the 300ms click delay, if user enable force
zoom.
> I thought for force zoom, both double tap and pinch zoom should work,
> that's why i raised this patch.
> 
> Could you please close the bug, i don't have permission to do it.

Done. Sorry to sink your patch after you've done it but I think this is the
right choice. Thanks anyway though, it's not obvious what's "correct" here.

[sujith, 2017-05-22 14:46:08]

Description was changed from

==========
DoubleTap Zoom support for Mobile Viewport pages

In case of ForceEnableZoom, MobileVieport pages not
supporting doubleTapZoom.
So added patch to support it.

BUG=701796
==========

to

==========
DoubleTap Zoom support for Mobile Viewport pages

In case of ForceEnableZoom, MobileVieport pages not
supporting doubleTapZoom.
So added patch to support it.

BUG=701796
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
==========

[sujith, 2017-05-31 11:01:09]

Patchset #2 (id:20001) has been deleted