Fix div by zero in GPU degenerate radials (and add sample and gm baselines)

Review URL: http://codereview.appspot.com/4675062/


git-svn-id: http://skia.googlecode.com/svn/trunk@1817 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 85 insertions, 0 deletions

diff --git a/samplecode/SampleDegenerateTwoPtRadials.cpp b/samplecode/SampleDegenerateTwoPtRadials.cpp
new file mode 100644
index 0000000000..ed10ce2304
--- /dev/null
+++ b/samplecode/SampleDegenerateTwoPtRadials.cpp
@@ -0,0 +1,85 @@
+#include "SampleCode.h"
+#include "SkView.h"
+#include "SkCanvas.h"
+#include "Sk64.h"
+#include "SkGradientShader.h"
+
+static void draw_gradient2(SkCanvas* canvas, const SkRect& rect, SkScalar delta) {
+    SkColor colors[] = { SK_ColorRED, SK_ColorGREEN, SK_ColorBLUE, SK_ColorMAGENTA };
+    SkScalar pos[] = { 0, SkFloatToScalar(0.25f), SkFloatToScalar(0.75f), SK_Scalar1 };
+
+    SkScalar l = rect.fLeft;
+    SkScalar t = rect.fTop;
+    SkScalar w = rect.width();
+    SkScalar h = rect.height();
+
+    SkASSERT(0 == SkScalarMod(w, SK_Scalar1 * 5));
+
+    SkPoint c0 = { l + 2 * w / 5 + delta, t + h / 2 };
+    SkPoint c1 = { l + 3 * w / 5, t + h / 2 };
+    SkScalar r0 = w / 5;
+    SkScalar r1 = 2 * w / 5;
+    SkShader* s = SkGradientShader::CreateTwoPointRadial(c0, r0, c1, r1, colors,
+                                                         pos, SK_ARRAY_COUNT(pos),
+                                                         SkShader::kClamp_TileMode);
+    SkPaint paint;
+    paint.setShader(s)->unref();
+
+    canvas->drawRect(rect, paint);
+}
+
+
+class DegenerateTwoPtRadialsView : public SampleView {
+
+public:
+    DegenerateTwoPtRadialsView() {
+        fTime = 0;
+        this->setBGColor(0xFFDDDDDD);
+    }
+
+protected:
+    // overrides from SkEventSink
+    virtual bool onQuery(SkEvent* evt) {
+        if (SampleCode::TitleQ(*evt)) {
+            SampleCode::TitleR(evt, "DegenerateTwoPtRadials");
+            return true;
+        }
+        return this->INHERITED::onQuery(evt);
+    }
+
+    virtual void onDrawContent(SkCanvas* canvas) {
+        fTime += SampleCode::GetAnimSecondsDelta();
+        SkScalar delta = fTime / 15.f;
+        int intPart = SkScalarFloor(delta);
+        delta = delta - SK_Scalar1 * intPart;
+        if (intPart % 2) {
+            delta = SK_Scalar1 - delta;
+        }
+        delta -= SK_ScalarHalf;
+        static const int DELTA_SCALE = 500;
+        delta /= DELTA_SCALE;
+
+        SkRect rect;
+        SkScalar w = SK_Scalar1 * 500;
+        SkScalar h = SK_Scalar1 * 500;
+        SkScalar l = SK_Scalar1 * 100;
+        SkScalar t = SK_Scalar1 * 100;
+        draw_gradient2(canvas, SkRect::MakeXYWH(l, t, w, h), delta);
+        char txt[512];
+        sprintf(txt, "gap at \"tangent\" pt = %f", SkScalarToFloat(delta));
+        SkPaint paint;
+        paint.setAntiAlias(true);
+        paint.setColor(SK_ColorBLACK);
+        canvas->drawText(txt, strlen(txt), l + w/2 + w*DELTA_SCALE*delta, t + h + SK_Scalar1 * 10, paint);
+        this->inval(NULL);
+    }
+
+private:
+    SkScalar           fTime;
+    typedef SampleView INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static SkView* MyFactory() { return new DegenerateTwoPtRadialsView; }
+static SkViewRegister reg(MyFactory);