gradient_many gm to test banding and precision

gm/gradients_no_texture.cpp

Index: gm/gradients_no_texture.cpp
diff --git a/gm/gradients_no_texture.cpp b/gm/gradients_no_texture.cpp
index 05481288fc422581cf98dc07a6d42e33c1793a70..cea1e8b382f76c854ff8014f0d1fd131ddfe9cf6 100644
--- a/gm/gradients_no_texture.cpp
+++ b/gm/gradients_no_texture.cpp
@@ -127,4 +127,131 @@ private:
 
 ///////////////////////////////////////////////////////////////////////////////
 
+struct ColorPos {
+    SkColor*    fColors;
+    SkScalar*   fPos;
+    int         fCount;
+
+    ColorPos() : fColors(NULL), fPos(NULL), fCount(0) {}
+    ~ColorPos() {
+        SkDELETE(fColors);
+        SkDELETE(fPos);
+    }
+
+    void construct(const SkColor colors[], const SkScalar pos[], int count) {
+        fColors = SkNEW_ARRAY(SkColor, count);
+        memcpy(fColors, colors, count * sizeof(SkColor));
+        if (pos) {
+            fPos = SkNEW_ARRAY(SkScalar, count);
+            memcpy(fPos, pos, count * sizeof(SkScalar));
+            fPos[0] = 0;
+            fPos[count - 1] = 1;
+        }
+        fCount = count;
+    }
+};
+
+static void make0(ColorPos* rec) {
+#if 0
+    From http://jsfiddle.net/3fe2a/
+
+background-image: -webkit-linear-gradient(left, #22d1cd 1%, #22d1cd 0.9510157507590116%, #df4b37 2.9510157507590113%, #df4b37 23.695886056604927%, #22d1cd 25.695886056604927%, #22d1cd 25.39321881940624%, #e6de36 27.39321881940624%, #e6de36 31.849399922570655%, #3267ff 33.849399922570655%, #3267ff 44.57735802921938%, #9d47d1 46.57735802921938%, #9d47d1 53.27185850805876%, #3267ff 55.27185850805876%, #3267ff 61.95718972227316%, #5cdd9d 63.95718972227316%, #5cdd9d 69.89166004442%, #3267ff 71.89166004442%, #3267ff 74.45795382765857%, #9d47d1 76.45795382765857%, #9d47d1 82.78364610713776%, #3267ff 84.78364610713776%, #3267ff 94.52743647737229%, #e3d082 96.52743647737229%, #e3d082 96.03934633331295%);
+height: 30px;
+#endif
+
+    const SkColor colors[] = {
+        0xFF22d1cd, 0xFF22d1cd, 0xFFdf4b37, 0xFFdf4b37, 0xFF22d1cd, 0xFF22d1cd, 0xFFe6de36, 0xFFe6de36,
+        0xFF3267ff, 0xFF3267ff, 0xFF9d47d1, 0xFF9d47d1, 0xFF3267ff, 0xFF3267ff, 0xFF5cdd9d, 0xFF5cdd9d,
+        0xFF3267ff, 0xFF3267ff, 0xFF9d47d1, 0xFF9d47d1, 0xFF3267ff, 0xFF3267ff, 0xFFe3d082, 0xFFe3d082
+    };
+    const double percent[] = {
+        1, 0.9510157507590116, 2.9510157507590113, 23.695886056604927,
+        25.695886056604927, 25.39321881940624, 27.39321881940624, 31.849399922570655,
+        33.849399922570655, 44.57735802921938, 46.57735802921938, 53.27185850805876,
+        55.27185850805876, 61.95718972227316, 63.95718972227316, 69.89166004442,
+        71.89166004442, 74.45795382765857, 76.45795382765857, 82.78364610713776,
+        84.78364610713776, 94.52743647737229, 96.52743647737229, 96.03934633331295,
+    };
+    const int N = SK_ARRAY_COUNT(percent);
+    SkScalar pos[N];
+    for (int i = 0; i < N; ++i) {
+        pos[i] = SkDoubleToScalar(percent[i] / 100);
+    }
+    rec->construct(colors, pos, N);
+}
+
+static void make1(ColorPos* rec) {
+    const SkColor colors[] = {
+        SK_ColorBLACK, SK_ColorWHITE, SK_ColorBLACK, SK_ColorWHITE,
+        SK_ColorBLACK, SK_ColorWHITE, SK_ColorBLACK, SK_ColorWHITE,
+        SK_ColorBLACK,
+    };
+    rec->construct(colors, NULL, SK_ARRAY_COUNT(colors));
+}
+
+static void make2(ColorPos* rec) {
+    const SkColor colors[] = {
+        SK_ColorBLACK, SK_ColorWHITE, SK_ColorBLACK, SK_ColorWHITE,
+        SK_ColorBLACK, SK_ColorWHITE, SK_ColorBLACK, SK_ColorWHITE,
+        SK_ColorBLACK,
+    };
+    const int N = SK_ARRAY_COUNT(colors);
+    SkScalar pos[N];
+    for (int i = 0; i < N; ++i) {
+        pos[i] = SK_Scalar1 * i / (N - 1);
+    }
+    rec->construct(colors, pos, N);
+}
+
+class GradientsManyColorsGM : public GM {
+    enum {
+        W = 800,
+    };
+    SkAutoTUnref<SkShader> fShader;
+
+    typedef void (*Proc)(ColorPos*);
+public:
+    GradientsManyColorsGM() {}
+    
+protected:
+    SkString onShortName() SK_OVERRIDE { return SkString("gradients_many"); }
+    virtual SkISize onISize() SK_OVERRIDE { return SkISize::Make(850, 100); }
+    
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        const Proc procs[] = {
+            make0, make1, make2,
+        };
+        const SkPoint pts[] = {
+            { 0, 0 },
+            { SkIntToScalar(W), 0 },
+        };
+        const SkRect r = SkRect::MakeWH(SkIntToScalar(W), 30);
+
+        SkPaint paint;
+        
+        canvas->translate(20, 20);
+        
+        for (int i = 0; i <= 8; ++i) {
+            SkScalar x = r.width() * i / 8;
+            canvas->drawLine(x, 0, x, 10000, paint);
+        }
+
+        for (size_t i = 0; i < SK_ARRAY_COUNT(procs); ++i) {
+            ColorPos rec;
+            procs[i](&rec);
+            SkShader* s = SkGradientShader::CreateLinear(pts, rec.fColors, rec.fPos, rec.fCount,
+                                                         SkShader::kClamp_TileMode);
+            paint.setShader(s)->unref();
+            canvas->drawRect(r, paint);
+            canvas->translate(0, r.height() + 20);
+        }
+    }
+    
+private:
+    typedef GM INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
 DEF_GM( return SkNEW(GradientsNoTextureGM));
+DEF_GM( return SkNEW(GradientsManyColorsGM));