Very tiny paths are subsumed by the Convexicator

and are treated as convex when they are not.

Allow the SkPath::Iter to leave degenerate path
segments unmolested by passing an additional exact
bool to next().

Treat any non-zero length as significant in addPt().

R=reed@google.com,robertphillips@google.com
BUG=493450

Review URL: https://codereview.chromium.org/1228383002

4 files changed, 84 insertions, 16 deletions

diff --git a/include/core/SkPath.h b/include/core/SkPath.h
index 99f8242ff7..fe89766558 100644
--- a/include/core/SkPath.h
+++ b/include/core/SkPath.h
@@ -206,8 +206,8 @@ public:
 
         @return true if the line is of zero length; otherwise false.
     */
-    static bool IsLineDegenerate(const SkPoint& p1, const SkPoint& p2) {
-        return p1.equalsWithinTolerance(p2);
+    static bool IsLineDegenerate(const SkPoint& p1, const SkPoint& p2, bool exact) {
+        return exact ? p1 == p2 : p1.equalsWithinTolerance(p2);
     }
 
     /** Test a quad for zero length
@@ -215,8 +215,8 @@ public:
         @return true if the quad is of zero length; otherwise false.
     */
     static bool IsQuadDegenerate(const SkPoint& p1, const SkPoint& p2,
-                                 const SkPoint& p3) {
-        return p1.equalsWithinTolerance(p2) &&
+                                 const SkPoint& p3, bool exact) {
+        return exact ? p1 == p2 && p2 == p3 : p1.equalsWithinTolerance(p2) &&
                p2.equalsWithinTolerance(p3);
     }
 
@@ -225,8 +225,8 @@ public:
         @return true if the cubic is of zero length; otherwise false.
     */
     static bool IsCubicDegenerate(const SkPoint& p1, const SkPoint& p2,
-                                  const SkPoint& p3, const SkPoint& p4) {
-        return p1.equalsWithinTolerance(p2) &&
+                                  const SkPoint& p3, const SkPoint& p4, bool exact) {
+        return exact ? p1 == p2 && p2 == p3 && p3 == p4 : p1.equalsWithinTolerance(p2) &&
                p2.equalsWithinTolerance(p3) &&
                p3.equalsWithinTolerance(p4);
     }
@@ -800,11 +800,15 @@ public:
             @param  pts The points representing the current verb and/or segment
             @param doConsumeDegerates If true, first scan for segments that are
                    deemed degenerate (too short) and skip those.
+            @param exact if doConsumeDegenerates is true and exact is true, skip only
+                   degenerate elements with lengths exactly equal to zero. If exact
+                   is false, skip degenerate elements with lengths close to zero. If
+                   doConsumeDegenerates is false, exact has no effect.
             @return The verb for the current segment
         */
-        Verb next(SkPoint pts[4], bool doConsumeDegerates = true) {
+        Verb next(SkPoint pts[4], bool doConsumeDegerates = true, bool exact = false) {
             if (doConsumeDegerates) {
-                this->consumeDegenerateSegments();
+                this->consumeDegenerateSegments(exact);
             }
             return this->doNext(pts);
         }
@@ -844,7 +848,7 @@ public:
 
         inline const SkPoint& cons_moveTo();
         Verb autoClose(SkPoint pts[2]);
-        void consumeDegenerateSegments();
+        void consumeDegenerateSegments(bool exact);
         Verb doNext(SkPoint pts[4]);
     };
 
diff --git a/src/core/SkPath.cpp b/src/core/SkPath.cpp
index 9381f48f3b..05fc7305ce 100644
--- a/src/core/SkPath.cpp
+++ b/src/core/SkPath.cpp
@@ -1612,7 +1612,7 @@ const SkPoint& SkPath::Iter::cons_moveTo() {
     }
 }
 
-void SkPath::Iter::consumeDegenerateSegments() {
+void SkPath::Iter::consumeDegenerateSegments(bool exact) {
     // We need to step over anything that will not move the current draw point
     // forward before the next move is seen
     const uint8_t* lastMoveVerb = 0;
@@ -1643,7 +1643,7 @@ void SkPath::Iter::consumeDegenerateSegments() {
                 break;
 
             case kLine_Verb:
-                if (!IsLineDegenerate(lastPt, fPts[0])) {
+                if (!IsLineDegenerate(lastPt, fPts[0], exact)) {
                     if (lastMoveVerb) {
                         fVerbs = lastMoveVerb;
                         fPts = lastMovePt;
@@ -1659,7 +1659,7 @@ void SkPath::Iter::consumeDegenerateSegments() {
 
             case kConic_Verb:
             case kQuad_Verb:
-                if (!IsQuadDegenerate(lastPt, fPts[0], fPts[1])) {
+                if (!IsQuadDegenerate(lastPt, fPts[0], fPts[1], exact)) {
                     if (lastMoveVerb) {
                         fVerbs = lastMoveVerb;
                         fPts = lastMovePt;
@@ -1675,7 +1675,7 @@ void SkPath::Iter::consumeDegenerateSegments() {
                 break;
 
             case kCubic_Verb:
-                if (!IsCubicDegenerate(lastPt, fPts[0], fPts[1], fPts[2])) {
+                if (!IsCubicDegenerate(lastPt, fPts[0], fPts[1], fPts[2], exact)) {
                     if (lastMoveVerb) {
                         fVerbs = lastMoveVerb;
                         fPts = lastMovePt;
@@ -2116,7 +2116,7 @@ struct Convexicator {
             SkScalar lengthSqd = vec.lengthSqd();
             if (!SkScalarIsFinite(lengthSqd)) {
                 fIsFinite = false;
-            } else if (!SkScalarNearlyZero(lengthSqd, SK_ScalarNearlyZero*SK_ScalarNearlyZero)) {
+            } else if (lengthSqd) {
                 fPriorPt = fLastPt;
                 fLastPt = fCurrPt;
                 fCurrPt = pt;
@@ -2253,7 +2253,7 @@ SkPath::Convexity SkPath::internalGetConvexity() const {
     if (!isFinite()) {
         return kUnknown_Convexity;
     }
-    while ((verb = iter.next(pts)) != SkPath::kDone_Verb) {
+    while ((verb = iter.next(pts, true, true)) != SkPath::kDone_Verb) {
         switch (verb) {
             case kMove_Verb:
                 if (++contourCount > 1) {
diff --git a/src/core/SkStroke.cpp b/src/core/SkStroke.cpp
index 86c0571c4b..d21dc96713 100644
--- a/src/core/SkStroke.cpp
+++ b/src/core/SkStroke.cpp
@@ -356,7 +356,7 @@ void SkPathStroker::line_to(const SkPoint& currPt, const SkVector& normal) {
 }
 
 void SkPathStroker::lineTo(const SkPoint& currPt) {
-    if (SkPath::IsLineDegenerate(fPrevPt, currPt)) {
+    if (SkPath::IsLineDegenerate(fPrevPt, currPt, false)) {
         return;
     }
     SkVector    normal, unitNormal;
diff --git a/tests/PathTest.cpp b/tests/PathTest.cpp
index d7660a196b..313d84a142 100644
--- a/tests/PathTest.cpp
+++ b/tests/PathTest.cpp
@@ -419,6 +419,68 @@ static void test_crbug_170666() {
     surface->getCanvas()->drawPath(path, paint);
 }
 
+
+static void test_tiny_path_convexity(skiatest::Reporter* reporter, const char* pathBug,
+        SkScalar tx, SkScalar ty, SkScalar scale) {
+    SkPath smallPath;
+    SkAssertResult(SkParsePath::FromSVGString(pathBug, &smallPath));
+    bool smallConvex = smallPath.isConvex();
+    SkPath largePath;
+    SkAssertResult(SkParsePath::FromSVGString(pathBug, &largePath));
+    SkMatrix matrix;
+    matrix.reset();
+    matrix.preTranslate(100, 100);
+    matrix.preScale(scale, scale);
+    largePath.transform(matrix);
+    bool largeConvex = largePath.isConvex();
+    REPORTER_ASSERT(reporter, smallConvex == largeConvex);
+}
+
+static void test_crbug_493450(skiatest::Reporter* reporter) {
+    const char reducedCase[] =
+        "M0,0"
+        "L0.0002, 0"
+        "L0.0002, 0.0002"
+        "L0.0001, 0.0001"
+        "L0,0.0002"
+        "Z";
+    test_tiny_path_convexity(reporter, reducedCase, 100, 100, 100000);
+    const char originalFiddleData[] =
+        "M-0.3383152268862998,-0.11217565719203619L-0.33846085183212765,-0.11212264406895281"
+        "L-0.338509393480737,-0.11210607966681395L-0.33857792286700894,-0.1121889121487573"
+        "L-0.3383866116636664,-0.11228834570924921L-0.33842087635680235,-0.11246078673250548"
+        "L-0.33809536177201055,-0.11245415228342878L-0.33797257995493996,-0.11216571641452182"
+        "L-0.33802112160354925,-0.11201996164188659L-0.33819815585141844,-0.11218559834671019Z";
+    test_tiny_path_convexity(reporter, originalFiddleData, 280081.4116670522f, 93268.04618493588f,
+            826357.3384828606f);
+}
+
+static void test_crbug_495894(skiatest::Reporter* reporter) {
+    const char originalFiddleData[] =
+        "M-0.34004273849857214,-0.11332803232216355L-0.34008271397389744,-0.11324483772714951"
+        "L-0.3401940742265893,-0.11324483772714951L-0.34017694188002134,-0.11329807920275889"
+        "L-0.3402026403998733,-0.11333468903941245L-0.34029972369709194,-0.11334134592705701"
+        "L-0.3403054344792813,-0.11344121970007795L-0.3403140006525653,-0.11351115418399343"
+        "L-0.34024261587519866,-0.11353446986281181L-0.3402197727464413,-0.11360442946144192"
+        "L-0.34013696640469604,-0.11359110237029302L-0.34009128014718143,-0.1135877707043939"
+        "L-0.3400598708451401,-0.11360776134112742L-0.34004273849857214,-0.11355112520064405"
+        "L-0.3400113291965308,-0.11355112520064405L-0.3399970522410575,-0.11359110237029302"
+        "L-0.33997135372120546,-0.11355112520064405L-0.3399627875479215,-0.11353780084493197"
+        "L-0.3399485105924481,-0.11350782354357004L-0.3400027630232468,-0.11346452910331437"
+        "L-0.3399485105924481,-0.11340126558629839L-0.33993994441916414,-0.11340126558629839"
+        "L-0.33988283659727087,-0.11331804756574679L-0.33989140277055485,-0.11324483772714951"
+        "L-0.33997991989448945,-0.11324483772714951L-0.3399856306766788,-0.11324483772714951"
+        "L-0.34002560615200417,-0.11334467443478255ZM-0.3400684370184241,-0.11338461985124307"
+        "L-0.340154098751264,-0.11341791238732665L-0.340162664924548,-0.1134378899559977"
+        "L-0.34017979727111597,-0.11340126558629839L-0.3401655203156427,-0.11338129083212668"
+        "L-0.34012268944922275,-0.11332137577529414L-0.34007414780061346,-0.11334467443478255Z"
+        "M-0.3400027630232468,-0.11290567901106024L-0.3400113291965308,-0.11298876531245433"
+        "L-0.33997991989448945,-0.11301535852306784L-0.33990282433493346,-0.11296217481488612"
+        "L-0.33993994441916414,-0.11288906492739594Z";
+    test_tiny_path_convexity(reporter, originalFiddleData, 22682.240000000005f,7819.72220766405f,
+            65536);
+}
+
 static void test_addrect(skiatest::Reporter* reporter) {
     SkPath path;
     path.lineTo(0, 0);
@@ -3758,6 +3820,8 @@ DEF_TEST(Paths, reporter) {
     test_tricky_cubic();
     test_clipped_cubic();
     test_crbug_170666();
+    test_crbug_493450(reporter);
+    test_crbug_495894(reporter);
     test_bad_cubic_crbug229478();
     test_bad_cubic_crbug234190();
     test_gen_id(reporter);