Allow mousewheel scrolling to work in print preview on HiDPI devices

Allow mousewheel scrolling to work in print preview on HiDPI devices

Right now, due to crbug.com/455439 mouse wheel scrolling doesn't work in print
preview on HiDPI devices. This hack forces the margins onto separate layers
to work around the bug until it's fixed.

BUG=455439
Committed: https://crrev.com/957b7b651c5fdd8ecfd31d010bde08bc9ac50b38
Cr-Commit-Position: refs/heads/master@{#315898}

[raymes, 2015-02-09 06:21:00]

raymes@chromium.org changed reviewers:
+ alekseys@chromium.org, rbyers@chromium.org

[Rick Byers, 2015-02-09 06:36:08]

What about fixing the weird clip?  Without fixing that, promoting these to a
layer will eat up a lot more GPU memory (each layer was full screen if I recall
- when really it should be just the side of the clickable handle you want).

[Rick Byers, 2015-02-09 06:37:03]

On 2015/02/09 06:36:08, Rick Byers wrote:
> What about fixing the weird clip?  Without fixing that, promoting these to a
> layer will eat up a lot more GPU memory (each layer was full screen if I
recall
> - when really it should be just the side of the clickable handle you want).

sorry - s/side/size/

[raymes, 2015-02-09 06:51:32]

It looks like the margins get placed on small layers by doing this (at least I
think so).

Also, it turned out to be very hard to fix the clip properly. Adjusting the
length of the margins was easy, but making them disappear at the right time if
they were fully obscured was hard. For example, if you scroll and a vertical
margin starts to cover the vertical scrollbar then you want to hide it. But
hiding it at the right time wasn't easy (if the clickable-padding covers the
scrollbar then it interferes with scrolling, but at that point the margin hasn't
actually visually obscured the scrollbar).

Thanks!

[Rick Byers, 2015-02-09 06:56:41]

On 2015/02/09 06:51:32, raymes wrote:
> It looks like the margins get placed on small layers by doing this (at least I
> think so).
> 
> Also, it turned out to be very hard to fix the clip properly. Adjusting the
> length of the margins was easy, but making them disappear at the right time if
> they were fully obscured was hard. For example, if you scroll and a vertical
> margin starts to cover the vertical scrollbar then you want to hide it. But
> hiding it at the right time wasn't easy (if the clickable-padding covers the
> scrollbar then it interferes with scrolling, but at that point the margin
hasn't
> actually visually obscured the scrollbar).
> 
> Thanks!

Ok, if this is creating small layers (i.e. with 'show composited layer borders'
or ideally the 'layers panel' I showed you) then this LGTM.

[raymes, 2015-02-09 23:56:34]

Hey Rick, I had a closer look and the large layers are still there unfortunately
:(. However given that this is not significantly worse than what is existing,
I'd like to move forward with this. I spent several hours trying to get rid of
the clip rect yesterday but, as I mentioned, it is hard and unfortunately I
don't have the time to spend on it right now. I can file it as a separate print
preview performance bug if you like.

Please let me know if that sounds ok. Thanks!

[Rick Byers, 2015-02-10 00:59:26]

On 2015/02/09 23:56:34, raymes wrote:
> Hey Rick, I had a closer look and the large layers are still there
unfortunately
> :(. However given that this is not significantly worse than what is existing,
> I'd like to move forward with this. I spent several hours trying to get rid of
> the clip rect yesterday but, as I mentioned, it is hard and unfortunately I
> don't have the time to spend on it right now. I can file it as a separate
print
> preview performance bug if you like.
> 
> Please let me know if that sounds ok. Thanks!

Ok, this should be very temporary anyway.  I think Majid has what he needs to
fix the chrome bug.  The hopefully you can revert this change.  LGTM.  Sorry for
all the trouble.

[raymes, 2015-02-10 01:10:16]

On 2015/02/10 00:59:26, Rick Byers wrote:
> On 2015/02/09 23:56:34, raymes wrote:
> > Hey Rick, I had a closer look and the large layers are still there
> unfortunately
> > :(. However given that this is not significantly worse than what is
existing,
> > I'd like to move forward with this. I spent several hours trying to get rid
of
> > the clip rect yesterday but, as I mentioned, it is hard and unfortunately I
> > don't have the time to spend on it right now. I can file it as a separate
> print
> > preview performance bug if you like.
> > 
> > Please let me know if that sounds ok. Thanks!
> 
> Ok, this should be very temporary anyway.  I think Majid has what he needs to
> fix the chrome bug.  The hopefully you can revert this change.  LGTM.  Sorry
for
> all the trouble.

No problem, thank you for your help!

[raymes, 2015-02-10 01:16:55]

alekseys: please let me know if this is ok with you :)

On Tue Feb 10 2015 at 12:10:18 PM <raymes@chromium.org> wrote:

> On 2015/02/10 00:59:26, Rick Byers wrote:
> > On 2015/02/09 23:56:34, raymes wrote:
> > > Hey Rick, I had a closer look and the large layers are still there
> > unfortunately
> > > :(. However given that this is not significantly worse than what is
> existing,
> > > I'd like to move forward with this. I spent several hours trying to get
> > rid
> of
> > > the clip rect yesterday but, as I mentioned, it is hard and
> > unfortunately I
> > > don't have the time to spend on it right now. I can file it as a
> > separate
> > print
> > > preview performance bug if you like.
> > >
> > > Please let me know if that sounds ok. Thanks!
>
> > Ok, this should be very temporary anyway.  I think Majid has what he
> > needs to
> > fix the chrome bug.  The hopefully you can revert this change.  LGTM.
> > Sorry
> for
> > all the trouble.
>
> No problem, thank you for your help!
>
> https://codereview.chromium.org/912433002/
>

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[raymes, 2015-02-11 06:30:47]

Friendly ping :)

[Aleksey Shlyapnikov, 2015-02-12 00:07:43]

lgtm

[raymes, 2015-02-12 00:08:22]

The CQ bit was checked by raymes@chromium.org

[commit-bot: I haz the power, 2015-02-12 00:09:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/912433002/1

[commit-bot: I haz the power, 2015-02-12 01:06:12]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-12 01:06:52]

Patchset 1 (id:??) landed as
https://crrev.com/957b7b651c5fdd8ecfd31d010bde08bc9ac50b38
Cr-Commit-Position: refs/heads/master@{#315898}