commit 1c5fd18927d5a128a12d7d5fe27f08d898be1e5b
author Stephen White <senorblanco@chromium.org> Thu Jul 12 15:54:05 2018 -0400
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Fri Jul 13 03:00:24 2018 +0000
tree 5e48bba13222c836bf2845f27f644d199580991c
parent 9cdbf1942de5f5565f67ad2cd8ed472ff22974b9

GrTessellator: missing intersection rewind fix.

Some "missing" intersections (see
https://skia.googlesource.com/skia/+/89042d5f13a56d6b663657aa58f17593123a344e)
cause the active edge list to go out of order. In that case, we need
to rewind the active list, just as we do before edge splitting for
regular intersections.

BUG=860453

Change-Id: I1f7b32157a73b427a4fd94c14c1eb440f26c0743
Reviewed-on: https://skia-review.googlesource.com/141038
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 78616d4..3424ee3 100644
--- a/src/gpu/GrTessellator.cpp
+++ b/src/gpu/GrTessellator.cpp
@@ -1110,21 +1110,28 @@
     if (!left->fTop || !left->fBottom || !right->fTop || !right->fBottom) {
         return false;
     }
+    if (left->fTop == right->fTop || left->fBottom == right->fBottom) {
+        return false;
+    }
     if (c.sweep_lt(left->fTop->fPoint, right->fTop->fPoint)) {
         if (!left->isLeftOf(right->fTop)) {
+            rewind(activeEdges, current, right->fTop, c);
             return split_edge(left, right->fTop, activeEdges, current, c, alloc);
         }
     } else {
         if (!right->isRightOf(left->fTop)) {
+            rewind(activeEdges, current, left->fTop, c);
             return split_edge(right, left->fTop, activeEdges, current, c, alloc);
         }
     }
     if (c.sweep_lt(right->fBottom->fPoint, left->fBottom->fPoint)) {
         if (!left->isLeftOf(right->fBottom)) {
+            rewind(activeEdges, current, right->fBottom, c);
             return split_edge(left, right->fBottom, activeEdges, current, c, alloc);
         }
     } else {
         if (!right->isRightOf(left->fBottom)) {
+            rewind(activeEdges, current, left->fBottom, c);
             return split_edge(right, left->fBottom, activeEdges, current, c, alloc);
         }
     }

tests/TessellatingPathRendererTests.cpp

diff --git a/tests/TessellatingPathRendererTests.cpp b/tests/TessellatingPathRendererTests.cpp
index 2891131f..4b3b321 100644
--- a/tests/TessellatingPathRendererTests.cpp
+++ b/tests/TessellatingPathRendererTests.cpp
@@ -584,6 +584,22 @@
     return path;
 }
 
+// Reduction from crbug.com/860453. Tests a case where a "missing" intersection
+// requires the active edge list to go out-of-order.
+static SkPath create_path_41() {
+    SkPath path;
+    path.moveTo(72154931603311689728.0,   330.95965576171875);
+    path.lineTo(24053266013925408768.0,       78.11376953125);
+    path.lineTo(1.2031099003292404941e+20,  387.168731689453125);
+    path.lineTo(68859835992355373056.0,   346.55047607421875);
+    path.lineTo(76451708695451009024.0,     337.780029296875);
+    path.moveTo(-20815817797613387776.0, 18065700622522384384.0);
+    path.lineTo(-72144121204987396096.0,  142.855804443359375);
+    path.lineTo(72144121204987396096.0,  325.184783935546875);
+    path.lineTo(1.2347242901040791552e+20, 18065700622522384384.0);
+    return path;
+}
+
 static std::unique_ptr<GrFragmentProcessor> create_linear_gradient_processor(GrContext* ctx) {
 
     SkPoint pts[2] = { {0, 0}, {1, 1} };
@@ -684,4 +700,5 @@
     test_path(ctx, rtc.get(), create_path_38(), SkMatrix(), GrAAType::kCoverage);
     test_path(ctx, rtc.get(), create_path_39());
     test_path(ctx, rtc.get(), create_path_40());
+    test_path(ctx, rtc.get(), create_path_41(), SkMatrix(), GrAAType::kCoverage);
 }