fix for teeny strokes

Pass the scale before evaluating degenerate line segments.

This does not change other GMs.

R=reed@google.com
BUG=478337

Review URL: https://codereview.chromium.org/1418133007

2 files changed, 43 insertions, 5 deletions

diff --git a/gm/strokes.cpp b/gm/strokes.cpp
index e74d35f800..bd393829e0 100644
--- a/gm/strokes.cpp
+++ b/gm/strokes.cpp
@@ -158,6 +158,42 @@ private:
     typedef skiagm::GM INHERITED;
 };
 
+class TeenyStrokesGM : public skiagm::GM {
+
+    SkString onShortName() override {
+        return SkString("teenyStrokes");
+    }
+
+    SkISize onISize() override {
+        return SkISize::Make(W, H*2);
+    }
+
+    static void line(SkScalar scale, SkCanvas* canvas, SkColor color) {
+        SkPaint p;
+        p.setAntiAlias(true);
+        p.setStyle(SkPaint::kStroke_Style);
+        p.setColor(color);
+        canvas->translate(50, 0);
+	    canvas->save();
+        p.setStrokeWidth(scale * 5);
+	    canvas->scale(1 / scale, 1 / scale);
+        canvas->drawLine(20 * scale, 20 * scale, 20 * scale, 100 * scale, p);
+        canvas->drawLine(20 * scale, 20 * scale, 100 * scale, 100 * scale, p);
+        canvas->restore();
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        line(0.00005f, canvas, SK_ColorBLACK);
+        line(0.000045f, canvas, SK_ColorRED);
+        line(0.0000035f, canvas, SK_ColorGREEN);
+        line(0.000003f, canvas, SK_ColorBLUE);
+        line(0.000002f, canvas, SK_ColorBLACK);
+    }
+private:
+    typedef skiagm::GM INHERITED;
+};
+
+
 class Strokes2GM : public skiagm::GM {
     SkPath fPath;
 protected:
@@ -418,3 +454,4 @@ static skiagm::GMRegistry R3(F3);
 static skiagm::GMRegistry R4(F4);
 
 DEF_GM( return new ZeroLenStrokesGM; )
+DEF_GM( return new TeenyStrokesGM; )
diff --git a/src/core/SkStroke.cpp b/src/core/SkStroke.cpp
index 522a000712..e04d14aea5 100644
--- a/src/core/SkStroke.cpp
+++ b/src/core/SkStroke.cpp
@@ -51,10 +51,11 @@ static inline bool degenerate_vector(const SkVector& v) {
     return !SkPoint::CanNormalize(v.fX, v.fY);
 }
 
-static bool set_normal_unitnormal(const SkPoint& before, const SkPoint& after,
+static bool set_normal_unitnormal(const SkPoint& before, const SkPoint& after, SkScalar scale,
                                   SkScalar radius,
                                   SkVector* normal, SkVector* unitNormal) {
-    if (!unitNormal->setNormalize(after.fX - before.fX, after.fY - before.fY)) {
+    if (!unitNormal->setNormalize((after.fX - before.fX) * scale,
+            (after.fY - before.fY) * scale)) {
         return false;
     }
     unitNormal->rotateCCW();
@@ -244,7 +245,7 @@ bool SkPathStroker::preJoinTo(const SkPoint& currPt, SkVector* normal,
     SkScalar    prevX = fPrevPt.fX;
     SkScalar    prevY = fPrevPt.fY;
 
-    if (!set_normal_unitnormal(fPrevPt, currPt, fRadius, normal, unitNormal)) {
+    if (!set_normal_unitnormal(fPrevPt, currPt, fResScale, fRadius, normal, unitNormal)) {
         if (SkStrokerPriv::CapFactory(SkPaint::kButt_Cap) == fCapper) {
             return false;
         }
@@ -367,7 +368,7 @@ void SkPathStroker::line_to(const SkPoint& currPt, const SkVector& normal) {
 
 void SkPathStroker::lineTo(const SkPoint& currPt) {
     if (SkStrokerPriv::CapFactory(SkPaint::kButt_Cap) == fCapper
-            && SkPath::IsLineDegenerate(fPrevPt, currPt, false)) {
+            && fPrevPt.equalsWithinTolerance(currPt, SK_ScalarNearlyZero * fInvResScale)) {
         return;
     }
     SkVector    normal, unitNormal;
@@ -381,7 +382,7 @@ void SkPathStroker::lineTo(const SkPoint& currPt) {
 
 void SkPathStroker::setQuadEndNormal(const SkPoint quad[3], const SkVector& normalAB,
         const SkVector& unitNormalAB, SkVector* normalBC, SkVector* unitNormalBC) {
-    if (!set_normal_unitnormal(quad[1], quad[2], fRadius, normalBC, unitNormalBC)) {
+    if (!set_normal_unitnormal(quad[1], quad[2], fResScale, fRadius, normalBC, unitNormalBC)) {
         *normalBC = normalAB;
         *unitNormalBC = unitNormalAB;
     }