Fix SkATan2_255 fuzzer crash

Test for degenerate values after computing the ratio, instead of
attempting to catch all tricky cases upfront.

BUG=skia:6511

Change-Id: I8e3421675994dd68a1eff1af3f1456917dd1f9e1
Reviewed-on: https://skia-review.googlesource.com/13726
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>

1 files changed, 46 insertions, 0 deletions

diff --git a/tests/GradientTest.cpp b/tests/GradientTest.cpp
index ec2753dc96..732bfbc22b 100644
--- a/tests/GradientTest.cpp
+++ b/tests/GradientTest.cpp
@@ -480,6 +480,51 @@ static void test_linear_fuzzer(skiatest::Reporter*) {
     }
 }
 
+static void test_sweep_fuzzer(skiatest::Reporter*) {
+    static const SkColor gColors0[] = { 0x30303030, 0x30303030, 0x30303030 };
+    static const SkScalar   gPos0[] = { -47919293023455565225163489280.0f, 0, 1 };
+    static const SkScalar gMatrix0[9] = {
+        1.12116716e-13f,  0              ,  8.50489682e+16f,
+        4.1917041e-41f ,  3.51369881e-23f, -2.54344271e-26f,
+        9.61111907e+17f, -3.35263808e-29f, -1.35659403e+14f
+    };
+    static const struct {
+        SkPoint            fCenter;
+        const SkColor*     fColors;
+        const SkScalar*    fPos;
+        int                fCount;
+        const SkScalar*    fGlobalMatrix;
+    } gConfigs[] = {
+        {
+            { 0, 0 },
+            gColors0,
+            gPos0,
+            SK_ARRAY_COUNT(gColors0),
+            gMatrix0
+        },
+    };
+
+    sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(100, 100);
+    SkCanvas* canvas = surface->getCanvas();
+    SkPaint paint;
+
+    for (const auto& config : gConfigs) {
+        paint.setShader(SkGradientShader::MakeSweep(config.fCenter.x(),
+                                                    config.fCenter.y(),
+                                                    config.fColors,
+                                                    config.fPos,
+                                                    config.fCount));
+
+        SkAutoCanvasRestore acr(canvas, false);
+        if (config.fGlobalMatrix) {
+            SkMatrix m;
+            m.set9(config.fGlobalMatrix);
+            canvas->save();
+            canvas->concat(m);
+        }
+        canvas->drawPaint(paint);
+    }
+}
 
 DEF_TEST(Gradient, reporter) {
     TestGradientShaders(reporter);
@@ -493,4 +538,5 @@ DEF_TEST(Gradient, reporter) {
     test_clamping_overflow(reporter);
     test_degenerate_linear(reporter);
     test_linear_fuzzer(reporter);
+    test_sweep_fuzzer(reporter);
 }