Make shadow tessellators fail gracefully and add unit test for this.

Change-Id: I42a9d06a18928588347a6dea2f6150518ba29aa8
Reviewed-on: https://skia-review.googlesource.com/7886
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>

1 files changed, 61 insertions, 0 deletions

diff --git a/tests/ShadowUtilsTest.cpp b/tests/ShadowUtilsTest.cpp
new file mode 100644
index 0000000000..adcb5031f4
--- /dev/null
+++ b/tests/ShadowUtilsTest.cpp
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkCanvas.h"
+#include "SkPath.h"
+#include "SkShadowTessellator.h"
+#include "SkShadowUtils.h"
+#include "Test.h"
+
+void tessellate_shadow(skiatest::Reporter* reporter, const SkPath& path, bool expectSuccess) {
+    static constexpr SkScalar kRadius = 2.f;
+    static constexpr SkColor kUmbraColor = 0xFFFFFFFF;
+    static constexpr SkColor kPenumbraColor = 0x20202020;
+    auto verts = SkShadowVertices::MakeAmbient(path, kRadius, kUmbraColor, kPenumbraColor, true);
+    if (expectSuccess != SkToBool(verts)) {
+        ERRORF(reporter, "Expected shadow tessellation to % but it did not.",
+               expectSuccess ? "succeed" : "fail");
+    }
+    verts = SkShadowVertices::MakeAmbient(path, kRadius, kUmbraColor, kPenumbraColor, false);
+    if (expectSuccess != SkToBool(verts)) {
+        ERRORF(reporter, "Expected shadow tessellation to % but it did not.",
+               expectSuccess ? "succeed" : "fail");
+    }
+    verts = SkShadowVertices::MakeSpot(path, 1.5f, {0, 0}, kRadius, kUmbraColor, kPenumbraColor,
+                                       false);
+    if (expectSuccess != SkToBool(verts)) {
+        ERRORF(reporter, "Expected shadow tessellation to % but it did not.",
+               expectSuccess ? "succeed" : "fail");
+    }
+    verts = SkShadowVertices::MakeSpot(path, 1.5f, {0, 0}, kRadius, kUmbraColor, kPenumbraColor,
+                                       true);
+    if (expectSuccess != SkToBool(verts)) {
+        ERRORF(reporter, "Expected shadow tessellation to % but it did not.",
+               expectSuccess ? "succeed" : "fail");
+    }
+}
+
+DEF_TEST(ShadowUtils, reporter) {
+    SkCanvas canvas(100, 100);
+    // Currently SkShadowUtils doesn't really stupport cubics when compiled without SK_SUPPORT_GPU.
+    // However, this should now crash.
+    SkPath path;
+    path.cubicTo(100, 50, 20, 100, 0, 0);
+    tessellate_shadow(reporter, path, (bool)SK_SUPPORT_GPU);
+
+    // This line segment has no area and no shadow.
+    path.reset();
+    path.lineTo(10.f, 10.f);
+    tessellate_shadow(reporter, path, false);
+
+    // A series of colinear line segments
+    path.reset();
+    for (int i = 0; i < 10; ++i) {
+        path.lineTo((SkScalar)i, (SkScalar)i);
+    }
+    tessellate_shadow(reporter, path, false);
+}