Fix single leg Compose Shader crash.

R=halcanary@google.com

BUG=skia:6291

Change-Id: Ifa63dce2b06662e7b535a4f04e1f3f772c099122
Reviewed-on: https://skia-review.googlesource.com/9027
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Hal Canary <halcanary@google.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/tests/ShaderTest.cpp b/tests/ShaderTest.cpp
index e3d87a2886..06aca1c021 100644
--- a/tests/ShaderTest.cpp
+++ b/tests/ShaderTest.cpp
@@ -7,7 +7,10 @@
 
 #include "Test.h"
 #include "SkBitmap.h"
+#include "SkCanvas.h"
 #include "SkImage.h"
+#include "SkPerlinNoiseShader.h"
+#include "SkRRect.h"
 #include "SkShader.h"
 #include "SkSurface.h"
 #include "SkData.h"
@@ -58,3 +61,21 @@ DEF_TEST(Shader_isABitmap, reporter) {
     check_isabitmap(reporter, shader0.get(), W, H, tmx, tmy, localM);
     check_isabitmap(reporter, shader1.get(), W, H, tmx, tmy, localM);
 }
+
+// Make sure things are ok with just a single leg.
+DEF_TEST(ComposeShaderSingle, reporter) {
+    SkBitmap srcBitmap;
+    srcBitmap.allocN32Pixels(10, 10);
+    srcBitmap.eraseColor(SK_ColorRED);
+    SkCanvas canvas(srcBitmap);
+    SkPaint p;
+    p.setShader(
+        SkShader::MakeComposeShader(
+        SkShader::MakeEmptyShader(),
+        SkPerlinNoiseShader::MakeFractalNoise(1.0f, 1.0f, 2, 0.0f),
+        SkBlendMode::kClear));
+    SkRRect rr;
+    SkVector rd[] = {{0, 0}, {0, 0}, {0, 0}, {0, 0}};
+    rr.setRectRadii({0, 0, 0, 0}, rd);
+    canvas.drawRRect(rr, p);
+}