Fallback to moveTo when unable to find the first tangent in cubicTo

tests/PathTest.cpp

Index: tests/PathTest.cpp
diff --git a/tests/PathTest.cpp b/tests/PathTest.cpp
index 3941ad6e183946ff42f86a40434c87c8b5467f02..5c00b53ac5129dfff87ce438d008823c2ff6f96d 100644
--- a/tests/PathTest.cpp
+++ b/tests/PathTest.cpp
@@ -64,6 +64,37 @@ static void test_path_crbug364224() {
     canvas->drawPath(path, paint);
 }
 
+/**
+ * In debug mode, this path is causing an assertion to fail in
+ * SkPathStroker::preJoinTo() and, in Release, the use of an unitialized value.
+ */
+static void make_path_crbugskia2820(SkPath* path, skiatest::Reporter* reporter) {
+    SkPoint orig, p1, p2, p3;
+    orig = SkPoint::Make(SkIntToScalar(1), SkIntToScalar(1));

[reed1, 2014/08/20 19:07:18]

:)

I find this very hard to read. Looking right below, lines 101.. is very
readable, and does not generate any warnings. I think that patterns is worth
replicating.

[Rémi Piotaix, 2014/08/20 19:21:08]

Done.

+    p1 = SkPoint::Make(SkIntToScalar(1)-SK_ScalarNearlyZero, SkIntToScalar(1));
+    p2 = SkPoint::Make(SkIntToScalar(1), SkIntToScalar(1)+SK_ScalarNearlyZero);
+    p3 = SkPoint::Make(SkIntToScalar(2), SkIntToScalar(2));
+
+    REPORTER_ASSERT(reporter, SkPath::IsLineDegenerate(orig, p1));

[reed1, 2014/08/20 19:07:18]

These lines are testing some aspect of IsLineDegenerate, not testing anything
about stroking per-se, as we can always change how we implement stroking. The
only "real" bug here is that we read uninitialized memory, and/or fire an
assert. The purpose of a test is to exercise that, so that we see that neither
of those happen in the future.

[Rémi Piotaix, 2014/08/20 19:21:09]

Done.

+    REPORTER_ASSERT(reporter, SkPath::IsLineDegenerate(orig, p2));
+    REPORTER_ASSERT(reporter, !SkPath::IsLineDegenerate(p1, p2));
+    REPORTER_ASSERT(reporter, !SkPath::IsLineDegenerate(p2, p3));
+
+    path->reset();
+    path->moveTo(SkIntToScalar(1), SkIntToScalar(1));
+    path->cubicTo(p1, p2, p3);
+    path->close();
+}
+
+static void test_path_crbugskia2820(skiatest::Reporter* reporter) {//GrContext* context) {
+    SkPath path;
+    make_path_crbugskia2820(&path, reporter);
+
+    SkStrokeRec stroke(SkStrokeRec::kFill_InitStyle);
+    stroke.setStrokeStyle(2 * SK_Scalar1);
+    stroke.applyToPath(&path, path);
+}
+
 static void make_path0(SkPath* path) {
     // from  *  https://code.google.com/p/skia/issues/detail?id=1706
 
@@ -3553,4 +3584,5 @@ DEF_TEST(Paths, reporter) {
     PathTest_Private::TestPathTo(reporter);
     PathRefTest_Private::TestPathRef(reporter);
     test_dump(reporter);
+    test_path_crbugskia2820(reporter);
 }