Add new GM to exercise stroked line special case

gm/strokedlines.cpp

Index: gm/strokedlines.cpp
diff --git a/gm/strokedlines.cpp b/gm/strokedlines.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..f0eb6b45cf45b3093c5efef7dd97012dfa6c789c
--- /dev/null
+++ b/gm/strokedlines.cpp
@@ -0,0 +1,228 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+#include "SkBlurMaskFilter.h"
+#include "SkDashPathEffect.h"
+#include "SkGradientShader.h"
+#include "SkPaint.h"
+#include "SkPath.h"
+#include "SkPoint3.h"
+
+static const int kNumColumns = 6;
+static const int kNumRows = 8;
+static const int kRadius = 40;  // radius of the snowflake
+static const int kPad = 5;      // padding on both sides of the snowflake
+static const int kNumSpokes = 6;
+static const SkScalar kStrokeWidth = 5.0f;
+
+static void draw_fins(SkCanvas* canvas, const SkPoint& offset, float angle, const SkPaint& paint) {
+    SkScalar cos, sin;
+
+    // first fin
+    sin = SkScalarSinCos(angle + (SK_ScalarPI/4), &cos);
+    sin *= kRadius / 2.0f;
+    cos *= kRadius / 2.0f;
+
+    SkPath p;
+    p.moveTo(offset.fX, offset.fY);
+    p.lineTo(offset.fX + cos, offset.fY + sin);
+    canvas->drawPath(p, paint);
+
+    // second fin
+    sin = SkScalarSinCos(angle - (SK_ScalarPI/4), &cos);
+    sin *= kRadius / 2.0f;
+    cos *= kRadius / 2.0f;
+
+    p.reset();
+    p.moveTo(offset.fX, offset.fY);
+    p.lineTo(offset.fX + cos, offset.fY + sin);
+    canvas->drawPath(p, paint);
+}
+
+// draw a snowflake centered at the origin
+static void draw_snowflake(SkCanvas* canvas, const SkPaint& paint) {
+
+    canvas->clipRect(SkRect::MakeLTRB(-kRadius-kPad, -kRadius-kPad, kRadius+kPad, kRadius+kPad));
+
+    SkScalar sin, cos, angle = 0.0f;
+    for (int i = 0; i < kNumSpokes/2; ++i, angle += SK_ScalarPI/(kNumSpokes/2)) {
+        sin = SkScalarSinCos(angle, &cos);
+        sin *= kRadius;
+        cos *= kRadius;
+
+        // main spoke
+        SkPath p;
+        p.moveTo(-cos, -sin);
+        p.lineTo(cos, sin);
+        canvas->drawPath(p, paint);
+
+        // fins on positive side
+        const SkPoint posOffset = SkPoint::Make(0.5f * cos, 0.5f * sin);
+        draw_fins(canvas, posOffset, angle, paint);
+
+        // fins on negative side
+        const SkPoint negOffset = SkPoint::Make(-0.5f * cos, -0.5f * sin);
+        draw_fins(canvas, negOffset, angle+SK_ScalarPI, paint);
+    }
+}
+
+static void draw_row(SkCanvas* canvas, const SkPaint& paint, const SkMatrix& localMatrix) {
+    canvas->translate(kRadius+kPad, 0.0f);
+
+    for (auto cap : { SkPaint::kButt_Cap, SkPaint::kRound_Cap, SkPaint::kSquare_Cap }) {
+        for (auto isAA : { true, false }) {
+            SkPaint tmp(paint);
+            tmp.setStrokeWidth(kStrokeWidth);
+            tmp.setStyle(SkPaint::kStroke_Style);
+            tmp.setStrokeCap(cap);
+            tmp.setAntiAlias(isAA);
+
+            int saveCount = canvas->save();
+            canvas->concat(localMatrix);
+            draw_snowflake(canvas, tmp);
+            canvas->restoreToCount(saveCount);
+
+            canvas->translate(2*(kRadius+kPad), 0.0f);
+        }
+    }
+}
+
+namespace skiagm {
+
+// This GM exercises the special case of a stroked lines.
+// Various shaders are applied to ensure the coordinate spaces work out right.
+class StrokedLinesGM : public GM {
+public:
+    StrokedLinesGM() {
+        this->setBGColor(sk_tool_utils::color_to_565(0xFF1A65D7));
+    }
+
+protected:
+    SkString onShortName() override {
+        return SkString("strokedlines");
+    }
+
+    SkISize onISize() override {
+        return SkISize::Make(kNumColumns * (2*kRadius+2*kPad), kNumRows * (2*kRadius+2*kPad));
+    }
+
+    void onOnceBeforeDraw() override {
+        // paints
+        {
+            // basic white
+            SkPaint p;
+            p.setColor(SK_ColorWHITE);
+            fPaints.push_back(p);
+        }
+        {
+            // gradient
+            SkColor colors[] = { SK_ColorRED, SK_ColorGREEN };
+            SkPoint pts[] = { {-kRadius-kPad, -kRadius-kPad }, { kRadius+kPad, kRadius+kPad } };
+
+            SkPaint p;
+            p.setShader(SkGradientShader::MakeLinear(pts, colors, nullptr, 2,
+                                                     SkShader::kClamp_TileMode, 0, nullptr));
+
+            fPaints.push_back(p);
+        }
+        {
+            // dashing
+            SkScalar intervals[] = { kStrokeWidth, kStrokeWidth };
+            int intervalCount = (int) SK_ARRAY_COUNT(intervals);
+            SkPaint p;
+            p.setColor(SK_ColorWHITE);
+            p.setPathEffect(SkDashPathEffect::Make(intervals, intervalCount, kStrokeWidth));
+
+            fPaints.push_back(p);
+        }
+        {
+            // Bitmap shader
+            SkBitmap bm;
+            bm.allocN32Pixels(2, 2);
+            *bm.getAddr32(0, 0) = *bm.getAddr32(1, 1) = 0xFFFFFFFF;
+            *bm.getAddr32(1, 0) = *bm.getAddr32(0, 1) = 0x0;
+
+            SkMatrix m;
+            m.setRotate(12.0f);
+            m.preScale(3.0f, 3.0f);;
+
+            SkPaint p;
+            p.setShader(SkShader::MakeBitmapShader(bm,
+                                                   SkShader::kRepeat_TileMode,
+                                                   SkShader::kRepeat_TileMode,
+                                                   &m));
+            fPaints.push_back(p);
+        }
+        {
+            // blur
+            SkPaint p;
+            p.setColor(SK_ColorWHITE);
+            p.setMaskFilter(SkBlurMaskFilter::Make(kOuter_SkBlurStyle, 3.0f,
+                                                   SkBlurMaskFilter::kHighQuality_BlurFlag));
+            fPaints.push_back(p);
+        }
+
+        // matrices
+        {
+            // rotation
+            SkMatrix m;
+            m.setRotate(12.0f);
+
+            fMatrices.push_back(m);
+        }
+        {
+            // skew
+            SkMatrix m;
+            m.setSkew(0.3f, 0.5f);
+
+            fMatrices.push_back(m);
+        }
+        {
+            // perspective
+            SkMatrix m;
+            m.reset();
+            m.setPerspX(-SK_Scalar1 / 300);
+            m.setPerspY(SK_Scalar1 / 300);
+
+            fMatrices.push_back(m);
+        }
+
+        SkASSERT(kNumRows == fPaints.count() + fMatrices.count());
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        canvas->translate(0, kRadius+kPad);
+
+        for (int i = 0; i < fPaints.count(); ++i) {
+            int saveCount = canvas->save();
+            draw_row(canvas, fPaints[i], SkMatrix::I());
+            canvas->restoreToCount(saveCount);
+
+            canvas->translate(0, 2*(kRadius+kPad));
+        }
+
+        for (int i = 0; i < fMatrices.count(); ++i) {
+            int saveCount = canvas->save();
+            draw_row(canvas, fPaints[0], fMatrices[i]);
+            canvas->restoreToCount(saveCount);
+
+            canvas->translate(0, 2*(kRadius+kPad));
+        }
+    }
+
+private:
+    SkTArray<SkPaint> fPaints;
+    SkTArray<SkMatrix> fMatrices;
+
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM(return new StrokedLinesGM;)
+}