Add unit test for SkDashPathEffect::asPoints' culling

tests/DashPathEffectTest.cpp

Index: tests/DashPathEffectTest.cpp
diff --git a/tests/DashPathEffectTest.cpp b/tests/DashPathEffectTest.cpp
index 1e53058de8e65f1730934da17459d57f8ef25ac6..228aee9031881bc2c33ee05d59972ec902518d0e 100644
--- a/tests/DashPathEffectTest.cpp
+++ b/tests/DashPathEffectTest.cpp
@@ -1,3 +1,10 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
 #include "Test.h"
 
 #include "SkDashPathEffect.h"
@@ -19,3 +26,63 @@ DEF_TEST(DashPathEffectTest_crbug_348821, r) {
     buffer.writeFlattenable(dash);
     REPORTER_ASSERT(r, buffer.bytesWritten() > 12);  // We'd write 12 if broken, >=40 if not.
 }
+
+// Test out the asPoint culling behavior.
+DEF_TEST(DashPathEffectTest_asPoints, r) {
+
+    const SkScalar intervals[] = { 1.0f, 1.0f };
+    const int count = 2;
+    SkAutoTUnref<SkDashPathEffect> dash(SkDashPathEffect::Create(intervals, count, 0.0f));
+
+    SkRect cull = SkRect::MakeWH(1.0f, 1.0f);
+
+    const struct {
+        SkPoint fPts[2];
+        bool    fExpectedResult;
+    } testCases[] = {
+        { { { -5.0f,  0.5f }, { -4.0f,  0.5f } }, false },   // off to the left
+        { { {  4.0f,  0.5f }, {  5.0f,  0.5f } }, false },   // off to the right
+        { { {  0.5f,  4.0f }, {  0.5f,  5.0f } }, false },   // off the bottom
+        { { {  0.5f, -5.0f }, {  0.5f, -4.0f } }, false },   // off the top
+        { { {  0.5f,  0.2f }, {  0.5f,  0.8f } }, true  },   // entirely inside vertical
+        { { {  0.2f,  0.5f }, {  0.8f,  0.5f } }, true  },   // entirely inside horizontal
+        { { {  0.5f, -5.0f }, {  0.5f,  5.0f } }, true  },   // straddles both sides vertically
+        { { { -5.0f,  0.5f }, {  5.0f,  0.5f } }, true  },   // straddles both sides horizontally
+        { { {  0.5f, -5.0f }, {  0.5f,  0.5f } }, true  },   // straddles top
+        { { {  0.5f,  5.0f }, {  0.5f,  0.5f } }, true  },   // straddles bottom
+        { { { -5.0f,  0.5f }, {  0.5f,  0.5f } }, true  },   // straddles left
+        { { {  5.0f,  0.5f }, {  0.5f,  0.5f } }, true  },   // straddles right
+        { { {  0.5f,  0.5f }, {  0.5f,  0.5f } }, false },   // zero length
+    };
+
+    SkPaint paint;
+    paint.setStyle(SkPaint::kStroke_Style);
+    paint.setStrokeWidth(1.0f);
+    SkStrokeRec rec(paint);
+
+    static const int kNumMats = 3;
+    SkMatrix mats[kNumMats];
+    mats[0].reset();
+    mats[1].setRotate(90, 0.5f, 0.5f);
+    mats[2].setTranslate(10.0f, 10.0f);
+
+    for (int i = 0; i < kNumMats; ++i) {
+        for (int j = 0; j < (int)SK_ARRAY_COUNT(testCases); ++j) {
+            for (int k = 0; k < 2; ++k) {  // exercise alternating endpoints
+                SkPathEffect::PointData results;
+                SkPath src;
+
+                src.moveTo(testCases[j].fPts[k]);
+                src.lineTo(testCases[j].fPts[(k+1)%2]);
+
+                bool actualResult = dash->asPoints(&results, src, rec, mats[i], &cull);
+                if (i < 2) {
+                    REPORTER_ASSERT(r, actualResult == testCases[j].fExpectedResult);
+                } else {
+                    // On the third pass all the lines should be outside the translated cull rect
+                    REPORTER_ASSERT(r, !actualResult);
+                }
+            }
+        }
+    }
+}