commit 13f3d8d4bc6863c7d890781021555fb6f65936e0
author Stephen White <senorblanco@chromium.org> Fri Jun 22 10:19:20 2018 -0400
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Fri Jun 22 15:27:57 2018 +0000
tree 07d19a327907c47f351c7839f6e2d8eae3ee961a
parent b9177cfaa8f56cc2f561669dc4e68cf6d43f529d

GrTessellator: avoid split with zero primary and out-of-range secondary.

Sometimes the intersector will return an intersection which is on the
same primary sort criterion (eg., Y coordinate), but out-of-range on the
secondary. We shouldn't do splits in this case. The only case we really
care about is if it's less than one epsilon and greater than zero,
and thus numerically unsplittable.

Bug: 851914
Change-Id: Ia772763b6a66a14ca159cf409a832835244e83bc
Reviewed-on: https://skia-review.googlesource.com/136803
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>

src/gpu/GrTessellator.cpp

diff --git a/src/gpu/GrTessellator.cpp b/src/gpu/GrTessellator.cpp
index 2dd82a0..d6a64cd 100644
--- a/src/gpu/GrTessellator.cpp
+++ b/src/gpu/GrTessellator.cpp
@@ -1199,7 +1199,7 @@
 bool nearly_flat(Comparator& c, Edge* edge) {
     SkPoint diff = edge->fBottom->fPoint - edge->fTop->fPoint;
     float primaryDiff = c.fDirection == Comparator::Direction::kHorizontal ? diff.fX : diff.fY;
-    return fabs(primaryDiff) < std::numeric_limits<float>::epsilon();
+    return fabs(primaryDiff) < std::numeric_limits<float>::epsilon() && primaryDiff != 0.0f;
 }
 
 SkPoint clamp(SkPoint p, SkPoint min, SkPoint max, Comparator& c) {

tests/TessellatingPathRendererTests.cpp

diff --git a/tests/TessellatingPathRendererTests.cpp b/tests/TessellatingPathRendererTests.cpp
index 6f2d896..0b30fee 100644
--- a/tests/TessellatingPathRendererTests.cpp
+++ b/tests/TessellatingPathRendererTests.cpp
@@ -546,6 +546,20 @@
     return path;
 }
 
+// Reduction from crbug.com/851914.
+static SkPath create_path_38() {
+    SkPath path;
+    path.moveTo(14.400531768798828125, 17.711114883422851562);
+    path.lineTo(14.621990203857421875,   171563104293879808);
+    path.lineTo(14.027951240539550781,   872585759381520384);
+    path.lineTo( 14.0216827392578125,   872665817571917824);
+    path.lineTo(7.699314117431640625,    -3417320793833472);
+    path.moveTo(11.606547355651855469,       17.40966796875);
+    path.lineTo( 7642114886926860288, 21.08358001708984375);
+    path.lineTo(11.606547355651855469, 21.08358001708984375);
+    return path;
+}
+
 static std::unique_ptr<GrFragmentProcessor> create_linear_gradient_processor(GrContext* ctx) {
 
     SkPoint pts[2] = { {0, 0}, {1, 1} };
@@ -643,4 +657,5 @@
     test_path(ctx, rtc.get(), create_path_35());
     test_path(ctx, rtc.get(), create_path_36());
     test_path(ctx, rtc.get(), create_path_37());
+    test_path(ctx, rtc.get(), create_path_38(), SkMatrix(), GrAAType::kCoverage);
 }