Fix custom cursor transparency compositing on MacOS

Fix custom cursor transparency compositing on MacOS

Custom cursor images that were not premultiplied by alpha were
being treated as if they were premultiplied, which was causing
overflows in the compositing arithmetic, producing artifacts
on MacOS.

BUG=543310
TEST=content_unittests WebCursorTest.AlphaConversion
R=avi@chromium.org

Committed: https://crrev.com/579c26f9110c5e275cfc404f96d51e49a6da426f
Cr-Commit-Position: refs/heads/master@{#355329}

[Justin Novosad, 2015-10-21 04:23:53]

PTAL

[Avi (use Gerrit), 2015-10-21 04:30:54]

avi@chromium.org changed reviewers:
+ avi@chromium.org

[Avi (use Gerrit), 2015-10-21 04:30:55]

Hey, it's my web cursor code! ('Tho it's been awhile since I've played with it.)

The ideas are good, but your style needs work.

https://codereview.chromium.org/1416023002/diff/1/content/common/cursors/webc...
File content/common/cursors/webcursor_mac.mm (right):

https://codereview.chromium.org/1416023002/diff/1/content/common/cursors/webc...
content/common/cursors/webcursor_mac.mm:154: SkImageInfo imageInfo =
SkImageInfo::MakeN32(size.width(), size.height(), kUnpremul_SkAlphaType);
80 columns, please

https://codereview.chromium.org/1416023002/diff/1/content/common/cursors/webc...
File content/common/cursors/webcursor_unittest.cc (right):

https://codereview.chromium.org/1416023002/diff/1/content/common/cursors/webc...
content/common/cursors/webcursor_unittest.cc:225: // This round trip will
convert the cursor to unpremultiplied form
finish sentences with periods

https://codereview.chromium.org/1416023002/diff/1/content/common/cursors/webc...
content/common/cursors/webcursor_unittest.cc:236: // unpremultiplied
finish sentences with periods

"A second round trip" or "The second round trip"

s/alread/already/

https://codereview.chromium.org/1416023002/diff/1/content/common/cursors/webc...
content/common/cursors/webcursor_unittest.cc:247: // On MacOS, test roundtrip
through NSCursor conversion
finish sentences with periods

[Justin Novosad, 2015-10-21 04:42:30]

New patch

[Avi (use Gerrit), 2015-10-21 05:13:50]

https://codereview.chromium.org/1416023002/diff/20001/content/common/cursors/...
File content/common/cursors/webcursor_mac.mm (right):

https://codereview.chromium.org/1416023002/diff/20001/content/common/cursors/...
content/common/cursors/webcursor_mac.mm:155: kUnpremul_SkAlphaType);
Align this parameter with the first, and if it doesn't fit, move all parameters
to the second line.

https://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Function_Calls

[jochen (gone - plz use gerrit), 2015-10-21 13:25:40]

jochen@chromium.org changed reviewers:
- jochen@chromium.org

[jochen (gone - plz use gerrit), 2015-10-21 13:25:40]

deferring to avi

[Justin Novosad, 2015-10-21 13:35:09]

On 2015/10/21 13:25:40, jochen wrote:
> deferring to avi

new patch

[Justin Novosad, 2015-10-21 15:01:52]

Description was changed from

==========
Fix custom cursor transparency compositing on MacOS

Custom cursor images that were not premultiplied by alpha were
being treated as if they were premultiplied, which was causing
overflows in the compositing arithmetic, producing artifacts
on MacOS.

BUG=543310
TEST=content_unittests WebCursorTest.AlphaConversion
R=jochen@chromium.org
==========

to

==========
Fix custom cursor transparency compositing on MacOS

Custom cursor images that were not premultiplied by alpha were
being treated as if they were premultiplied, which was causing
overflows in the compositing arithmetic, producing artifacts
on MacOS.

BUG=543310
TEST=content_unittests WebCursorTest.AlphaConversion
R=avi@chromium.org
==========

[Avi (use Gerrit), 2015-10-21 16:27:08]

lgtm

Nice! Thanks for the fix.

[Justin Novosad, 2015-10-21 17:25:37]

The CQ bit was checked by junov@chromium.org

[commit-bot: I haz the power, 2015-10-21 17:26:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1416023002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1416023002/40001

[commit-bot: I haz the power, 2015-10-21 17:44:36]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-10-21 17:45:15]

Patchset 3 (id:??) landed as
https://crrev.com/579c26f9110c5e275cfc404f96d51e49a6da426f
Cr-Commit-Position: refs/heads/master@{#355329}