fix slowness of getImageData() for CanvasRenderingContext2D in linux due to un-optimized format for…

fix slowness of getImageData() for CanvasRenderingContext2D in linux due to un-optimized format for glReadPixels.

BUG=242093

[Jun Jiang, 2013-05-19 15:21:48]

This issue is found when investigating
http://code.google.com/p/chromium/issues/detail?id=235783. This fix can get 7x +
performance increase on ubuntu 12.04 with Mesa 8.0.4.

[bsalomon, 2013-05-20 13:04:00]

On 2013/05/19 15:21:48, Jun Jiang wrote:
> This issue is found when investigating
> http://code.google.com/p/chromium/issues/detail?id=235783. This fix can get 7x
+
> performance increase on ubuntu 12.04 with Mesa 8.0.4.

Can we fix this by returning the correct value from preferredReadPixelsConfig()
rather than not calling it. Otherwise this will slow down other platforms (ANGLE
in particular).

[Jun Jiang, 2013-05-21 15:26:26]

On 2013/05/20 13:04:00, bsalomon wrote:
> On 2013/05/19 15:21:48, Jun Jiang wrote:
> > This issue is found when investigating
> > http://code.google.com/p/chromium/issues/detail?id=235783. This fix can get
7x
> +
> > performance increase on ubuntu 12.04 with Mesa 8.0.4.
> 
> Can we fix this by returning the correct value from
preferredReadPixelsConfig()
> rather than not calling it. Otherwise this will slow down other platforms
(ANGLE
> in particular).
Hi, bsalonmon. Thanks for your comments.
Yes, there may be a case that the backend for Canvas2D texture is of format RGBA
format although currently what we see is of BGRA format for all platforms. It
may ruin the performance for Angle. Refined the patch accordingly and PTAL.
Thanks.

[bsalomon, 2013-05-22 15:00:07]

On 2013/05/21 15:26:26, Jun Jiang wrote:
> On 2013/05/20 13:04:00, bsalomon wrote:
> > On 2013/05/19 15:21:48, Jun Jiang wrote:
> > > This issue is found when investigating
> > > http://code.google.com/p/chromium/issues/detail?id=235783. This fix can
get
> 7x
> > +
> > > performance increase on ubuntu 12.04 with Mesa 8.0.4.
> > 
> > Can we fix this by returning the correct value from
> preferredReadPixelsConfig()
> > rather than not calling it. Otherwise this will slow down other platforms
> (ANGLE
> > in particular).
> Hi, bsalonmon. Thanks for your comments.
> Yes, there may be a case that the backend for Canvas2D texture is of format
RGBA
> format although currently what we see is of BGRA format for all platforms. It
> may ruin the performance for Angle. Refined the patch accordingly and PTAL.
> Thanks.

I've made some changes to this patch (mostly line-wraps, param names, and
comments) and uploaded it here: https://codereview.chromium.org/15746007 (since
codereview doesn't allow a second author to upload to an issue).

[Jun Jiang, 2013-05-22 16:58:13]

On 2013/05/22 15:00:07, bsalomon wrote:
> On 2013/05/21 15:26:26, Jun Jiang wrote:
> > On 2013/05/20 13:04:00, bsalomon wrote:
> > > On 2013/05/19 15:21:48, Jun Jiang wrote:
> > > > This issue is found when investigating
> > > > http://code.google.com/p/chromium/issues/detail?id=235783. This fix can
> get
> > 7x
> > > +
> > > > performance increase on ubuntu 12.04 with Mesa 8.0.4.
> > > 
> > > Can we fix this by returning the correct value from
> > preferredReadPixelsConfig()
> > > rather than not calling it. Otherwise this will slow down other platforms
> > (ANGLE
> > > in particular).
> > Hi, bsalonmon. Thanks for your comments.
> > Yes, there may be a case that the backend for Canvas2D texture is of format
> RGBA
> > format although currently what we see is of BGRA format for all platforms.
It
> > may ruin the performance for Angle. Refined the patch accordingly and PTAL.
> > Thanks.
> 
> I've made some changes to this patch (mostly line-wraps, param names, and
> comments) and uploaded it here: https://codereview.chromium.org/15746007
(since
> codereview doesn't allow a second author to upload to an issue).

Hi, bsalonmon. Thanks for your help on this.

[Jun Jiang, 2013-05-24 20:03:23]

On 2013/05/22 16:58:13, Jun Jiang wrote:
> On 2013/05/22 15:00:07, bsalomon wrote:
> > On 2013/05/21 15:26:26, Jun Jiang wrote:
> > > On 2013/05/20 13:04:00, bsalomon wrote:
> > > > On 2013/05/19 15:21:48, Jun Jiang wrote:
> > > > > This issue is found when investigating
> > > > > http://code.google.com/p/chromium/issues/detail?id=235783. This fix
can
> > get
> > > 7x
> > > > +
> > > > > performance increase on ubuntu 12.04 with Mesa 8.0.4.
> > > > 
> > > > Can we fix this by returning the correct value from
> > > preferredReadPixelsConfig()
> > > > rather than not calling it. Otherwise this will slow down other
platforms
> > > (ANGLE
> > > > in particular).
> > > Hi, bsalonmon. Thanks for your comments.
> > > Yes, there may be a case that the backend for Canvas2D texture is of
format
> > RGBA
> > > format although currently what we see is of BGRA format for all platforms.
> It
> > > may ruin the performance for Angle. Refined the patch accordingly and
PTAL.
> > > Thanks.
> > 
> > I've made some changes to this patch (mostly line-wraps, param names, and
> > comments) and uploaded it here: https://codereview.chromium.org/15746007
> (since
> > codereview doesn't allow a second author to upload to an issue).
> 
> Hi, bsalonmon. Thanks for your help on this.

Thanks for bsalonmon's help and it has been landed at
https://codereview.chromium.org/15746007. Close this issue now.