subdivide path when side-clipping fails

subdivide path when side-clipping fails

Please review concept; I'm OK not to check this in.

If the root finder fails, subdivide the curve and try again.
This is complicated by the reversed nature of the curves;
maybe it can be simpler, but how to do that escapes me.

R=reed@google.com
BUG=514246
Committed: https://skia.googlesource.com/skia/+/7d173403f47bb85cfd5c42b69c734668e25e47f9

[caryclark, 2015-08-19 19:15:17]

The CQ bit was checked by caryclark@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-08-19 19:15:29]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1299243002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1299243002/1

[commit-bot: I haz the power, 2015-08-19 19:22:24]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-19 19:22:25]

Dry run: This issue passed the CQ dry run.

[caryclark, 2015-08-19 20:49:44]

closer to real; please take a look

[caryclark, 2015-08-19 20:50:15]

The CQ bit was checked by caryclark@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-08-19 20:50:34]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1299243002/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1299243002/80001

[commit-bot: I haz the power, 2015-08-19 20:57:25]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-19 20:57:26]

Dry run: This issue passed the CQ dry run.

[reed1, 2015-08-19 20:57:49]

great small fix

lgtm

[caryclark, 2015-08-20 13:08:12]

I took your suggestion and rewrote in terms of ABCD. Then I realized that the
earlier CL would probably fail if the curve was very large, because the iterator
would give up too soon, while for very small curves, it would iterate too many
times.

I rewrote the iterator to choose the best answer, and to stop when either the
answer was within a 1/4 pixel or the t value quit changing.

Please take a look.

[caryclark, 2015-08-20 13:08:25]

The CQ bit was checked by caryclark@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-08-20 13:08:40]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1299243002/100001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1299243002/100001

[commit-bot: I haz the power, 2015-08-20 13:10:30]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-20 13:10:30]

Dry run: Try jobs failed on following builders:
  Build-Ubuntu-GCC-x86_64-Release-Trybot on client.skia.compile (JOB_FAILED,
http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu-GCC-x86...)

[caryclark, 2015-08-20 13:15:02]

The CQ bit was checked by caryclark@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-08-20 13:15:09]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1299243002/110003
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1299243002/110003

[commit-bot: I haz the power, 2015-08-20 13:22:42]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-20 13:22:42]

Dry run: This issue passed the CQ dry run.

[reed1, 2015-08-20 14:24:45]

looks good.

BTW -- seems like we can have exactly the same problem when we chop against
vertical lines. I guess we can try to rotate your test-case (swap X and Y) and
see if that's true. If so, we'll probably want to refactor this to "just" chop a
cubic ABCD so it can be called for Xs or Ys.

I'm also fine to land as is, and try testing the other case afterwards.

https://codereview.chromium.org/1299243002/diff/110003/src/core/SkEdgeClipper...
File src/core/SkEdgeClipper.cpp (right):

https://codereview.chromium.org/1299243002/diff/110003/src/core/SkEdgeClipper...
src/core/SkEdgeClipper.cpp:273: static void chop_mono_cubic_at_x(SkPoint pts[4],
SkScalar x, SkPoint tmp[7]) {
perhaps rename
pts -> src or orig
tmp -> dst or chopped or something

[caryclark, 2015-08-20 15:23:10]

The CQ bit was checked by caryclark@google.com

[caryclark, 2015-08-20 15:23:10]

The patchset sent to the CQ was uploaded after l-g-t-m from reed@google.com
Link to the patchset: https://codereview.chromium.org/1299243002/#ps110003
(title: "add init to avoid warning")

[commit-bot: I haz the power, 2015-08-20 15:23:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1299243002/110003
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1299243002/110003

[commit-bot: I haz the power, 2015-08-20 15:23:56]

Committed patchset #7 (id:110003) as
https://skia.googlesource.com/skia/+/7d173403f47bb85cfd5c42b69c734668e25e47f9