Filter out degenerate contours in GrConvexPolyEffect

Filter out degenerate contours in GrConvexPolyEffect

As noticed in a downstream Firefox bug report https://bugzilla.mozilla.org/show_bug.cgi?id=1255062

If a path such as (moveTo, moveTo, lineTo, lineTo, close) is supplied,
and if the non-degenerate contour is convex, the convexity test will
pass, and GrConvexPolyEffect will be used.

However, the path's raw points are used to build the edge list, which
does not filter out degenerate contours. This may cause the polygon to
fail to draw.

This patch ensures that the degenerate contours are filtered out by
using an iterator as the path convexity test does.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2018613003

Committed: https://skia.googlesource.com/skia/+/d15947ea4d2d0ceee797a973a90fc1e5f86772bd

[lsalzman1, 2016-05-26 19:03:38]

Description was changed from

==========
Filter out degenerate contours in GrConvexPolyEffect

As noticed in a downstream Firefox bug report...

If a path such as (moveTo, moveTo, lineTo, lineTo, close) is supplied,
and if the non-degenerate contour is convex, the convexity test will
pass, and GrConvexPolyEffect will be used.

However, the path's raw points are used to build the edge list, which
does not filter out degenerate contours. This may cause the polygon to
fail to draw.

This patch ensures that the degenerate contours are filtered out by
using an iterator as the path convexity test does.

BUG=skia:
==========

to

==========
Filter out degenerate contours in GrConvexPolyEffect

As noticed in a downstream Firefox bug report...

If a path such as (moveTo, moveTo, lineTo, lineTo, close) is supplied,
and if the non-degenerate contour is convex, the convexity test will
pass, and GrConvexPolyEffect will be used.

However, the path's raw points are used to build the edge list, which
does not filter out degenerate contours. This may cause the polygon to
fail to draw.

This patch ensures that the degenerate contours are filtered out by
using an iterator as the path convexity test does.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2018613003
==========

[lsalzman1, 2016-05-26 19:06:44]

Description was changed from

==========
Filter out degenerate contours in GrConvexPolyEffect

As noticed in a downstream Firefox bug report...

If a path such as (moveTo, moveTo, lineTo, lineTo, close) is supplied,
and if the non-degenerate contour is convex, the convexity test will
pass, and GrConvexPolyEffect will be used.

However, the path's raw points are used to build the edge list, which
does not filter out degenerate contours. This may cause the polygon to
fail to draw.

This patch ensures that the degenerate contours are filtered out by
using an iterator as the path convexity test does.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2018613003
==========

to

==========
Filter out degenerate contours in GrConvexPolyEffect

As noticed in a downstream Firefox bug report
https://bugzilla.mozilla.org/show_bug.cgi?id=1255062

If a path such as (moveTo, moveTo, lineTo, lineTo, close) is supplied,
and if the non-degenerate contour is convex, the convexity test will
pass, and GrConvexPolyEffect will be used.

However, the path's raw points are used to build the edge list, which
does not filter out degenerate contours. This may cause the polygon to
fail to draw.

This patch ensures that the degenerate contours are filtered out by
using an iterator as the path convexity test does.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2018613003
==========

[lsalzman1, 2016-05-26 19:06:44]

lsalzman@mozilla.com changed reviewers:
+ bsalomon@google.com

[bsalomon, 2016-05-27 20:30:31]

Looks ok to me.

https://codereview.chromium.org/2018613003/diff/1/src/gpu/effects/GrConvexPol...
File src/gpu/effects/GrConvexPolyEffect.cpp (right):

https://codereview.chromium.org/2018613003/diff/1/src/gpu/effects/GrConvexPol...
src/gpu/effects/GrConvexPolyEffect.cpp:275: while ((verb = iter.next(pts, true,
true)) != SkPath::kDone_Verb) {
Perhaps we should have a comment that has multiple moveTos followed by a convex
contour is considered convex by SkPath (hence the reason for iterating past the
moveTos here).

https://codereview.chromium.org/2018613003/diff/1/src/gpu/effects/GrConvexPol...
src/gpu/effects/GrConvexPolyEffect.cpp:277: case SkPath::kMove_Verb:
Should we assert here that n is 0?

[lsalzman1, 2016-05-28 00:24:57]

I added both code comments and assertions as requested.

[bsalomon, 2016-05-31 16:24:43]

lgtm

[lsalzman1, 2016-05-31 16:29:40]

The CQ bit was checked by lsalzman@mozilla.com

[commit-bot: I haz the power, 2016-05-31 16:29:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2018613003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/2018613003/20001

[commit-bot: I haz the power, 2016-05-31 16:46:05]

Description was changed from

==========
Filter out degenerate contours in GrConvexPolyEffect

As noticed in a downstream Firefox bug report
https://bugzilla.mozilla.org/show_bug.cgi?id=1255062

If a path such as (moveTo, moveTo, lineTo, lineTo, close) is supplied,
and if the non-degenerate contour is convex, the convexity test will
pass, and GrConvexPolyEffect will be used.

However, the path's raw points are used to build the edge list, which
does not filter out degenerate contours. This may cause the polygon to
fail to draw.

This patch ensures that the degenerate contours are filtered out by
using an iterator as the path convexity test does.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2018613003
==========

to

==========
Filter out degenerate contours in GrConvexPolyEffect

As noticed in a downstream Firefox bug report
https://bugzilla.mozilla.org/show_bug.cgi?id=1255062

If a path such as (moveTo, moveTo, lineTo, lineTo, close) is supplied,
and if the non-degenerate contour is convex, the convexity test will
pass, and GrConvexPolyEffect will be used.

However, the path's raw points are used to build the edge list, which
does not filter out degenerate contours. This may cause the polygon to
fail to draw.

This patch ensures that the degenerate contours are filtered out by
using an iterator as the path convexity test does.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2018613003

Committed:
https://skia.googlesource.com/skia/+/d15947ea4d2d0ceee797a973a90fc1e5f86772bd
==========

[commit-bot: I haz the power, 2016-05-31 16:46:07]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/d15947ea4d2d0ceee797a973a90fc1e5f86772bd