Fix bug in raster implementation of SkRRectsGaussianEdgeMaskFilter

The bug was the raster version didn't correctly handle the CTM.

This CL also adds a way to test the behavior (by translating the
reveal GM around in SampleApp)

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3729

Change-Id: Iaacc905167d20b453203307e5ef840f552fdbb38
Reviewed-on: https://skia-review.googlesource.com/3729
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>

gm/reveal.cpp

@@ -28,7 +28,9 @@ constexpr int kClipOffset = 32;
 class Object {
 public:
     virtual ~Object() {}
-    virtual bool asRRect(SkRRect* rr) const = 0;
+    // When it returns true, this call will have placed a device-space _circle, rect or 
+    // simple circular_ RRect in "rr"
+    virtual bool asDevSpaceRRect(const SkMatrix& ctm, SkRRect* rr) const = 0;
     virtual SkPath asPath(SkScalar inset) const = 0;
     virtual void draw(SkCanvas* canvas, const SkPaint& paint) const = 0;
     virtual void clip(SkCanvas* canvas) const = 0;
@@ -44,8 +46,24 @@ public:
         fRRect = SkRRect::MakeRectXY(r, 4*kPad, 4*kPad);
     }
 
-    bool asRRect(SkRRect* rr) const override {
-        *rr = fRRect;
+    bool asDevSpaceRRect(const SkMatrix& ctm, SkRRect* rr) const override {
+        if (!ctm.isSimilarity()) { // the corners have to remain circular
+            return false;
+        }
+
+        SkScalar scales[2];
+        if (!ctm.getMinMaxScales(scales)) {
+            return false;
+        }
+
+        SkASSERT(SkScalarNearlyEqual(scales[0], scales[1]));
+
+        SkRect devRect;
+        ctm.mapRect(&devRect, fRRect.rect());
+
+        SkScalar scaledRad = scales[0] * fRRect.getSimpleRadii().fX;
+
+        *rr = SkRRect::MakeRectXY(devRect, scaledRad, scaledRad);
         return true;
     }
 
@@ -88,7 +106,7 @@ public:
         fStrokedBounds = r.makeOutset(kPad, kPad);
     }
 
-    bool asRRect(SkRRect* rr) const override {
+    bool asDevSpaceRRect(const SkMatrix& ctm, SkRRect* rr) const override {
         return false;
     }
 
@@ -144,8 +162,14 @@ public:
         fRRect = SkRRect::MakeOval(r);
     }
 
-    bool asRRect(SkRRect* rr) const override {
-        *rr = fRRect;
+    bool asDevSpaceRRect(const SkMatrix& ctm, SkRRect* rr) const override {
+        if (!ctm.isSimilarity()) { // circles have to remain circles
+            return false;
+        }
+
+        SkRect devRect;
+        ctm.mapRect(&devRect, fRRect.rect());
+        *rr = SkRRect::MakeOval(devRect);
         return true;
     }
 
@@ -186,8 +210,14 @@ class Rect : public Object {
 public:
     Rect(const SkRect& r) : fRect(r) { }
 
-    bool asRRect(SkRRect* rr) const override {
-        *rr = SkRRect::MakeRect(fRect);
+    bool asDevSpaceRRect(const SkMatrix& ctm, SkRRect* rr) const override {
+        if (!ctm.rectStaysRect()) {
+            return false;
+        }
+
+        SkRect devRect;
+        ctm.mapRect(&devRect, fRect);
+        *rr = SkRRect::MakeRect(devRect);
         return true;
     }
 
@@ -246,7 +276,7 @@ public:
         fPath.close();
     }
 
-    bool asRRect(SkRRect* rr) const override {
+    bool asDevSpaceRRect(const SkMatrix& ctm, SkRRect* rr) const override {
         return false;
     }
 
@@ -311,6 +341,7 @@ public:
     }
 
 protected:
+    bool runAsBench() const override { return true; }
 
     SkString onShortName() override {
         return SkString("reveal");
@@ -393,10 +424,12 @@ protected:
 
                     SkPaint paint;
 
-                    SkRRect clipRR, drawnRR;
+                    SkRRect devSpaceClipRR, devSpaceDrawnRR;
 
-                    if (clipObj->asRRect(&clipRR) && drawObj->asRRect(&drawnRR)) {
-                        paint.setMaskFilter(SkRRectsGaussianEdgeMaskFilter::Make(clipRR, drawnRR,
+                    if (clipObj->asDevSpaceRRect(canvas->getTotalMatrix(), &devSpaceClipRR) &&
+                        drawObj->asDevSpaceRRect(canvas->getTotalMatrix(), &devSpaceDrawnRR)) {
+                        paint.setMaskFilter(SkRRectsGaussianEdgeMaskFilter::Make(devSpaceClipRR,
+                                                                                 devSpaceDrawnRR,
                                                                                  fBlurRadius));
                     }
 

src/effects/SkRRectsGaussianEdgeMaskFilter.cpp

@@ -160,7 +160,6 @@ bool SkRRectsGaussianEdgeMaskFilterImpl::filterMask(SkMask* dst, const SkMask& s
         uint8_t* dstPixels = dst->fImage = SkMask::AllocImage(dstSize);
 
         SkPoint basePt = { SkIntToScalar(src.fBounds.fLeft), SkIntToScalar(src.fBounds.fTop) };
-        matrix.mapPoints(&basePt, 1);
 
         for (int y = 0; y < dst->fBounds.height(); ++y) {
             const uint8_t* srcRow = srcPixels + y * dst->fRowBytes;