allow one zero length dash

If the constructed stroke that represents a dash has a
single dash of length zero, and the end cap is square or
round, draw the cap.

The old code initialized the initial dash length to zero,
making it ambiguous whether the first length is zero or
not.

R=robertphillips@google.com
BUG=583299
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1805963002

Review URL: https://codereview.chromium.org/1805963002

1 files changed, 4 insertions, 10 deletions

diff --git a/src/effects/SkDashPathEffect.cpp b/src/effects/SkDashPathEffect.cpp
index ced0aab69a..3816499915 100644
--- a/src/effects/SkDashPathEffect.cpp
+++ b/src/effects/SkDashPathEffect.cpp
@@ -14,7 +14,7 @@
 
 SkDashPathEffect::SkDashPathEffect(const SkScalar intervals[], int count, SkScalar phase)
         : fPhase(0)
-        , fInitialDashLength(0)
+        , fInitialDashLength(-1)
         , fInitialDashIndex(0)
         , fIntervalLength(0) {
     SkASSERT(intervals);
@@ -23,7 +23,6 @@ SkDashPathEffect::SkDashPathEffect(const SkScalar intervals[], int count, SkScal
     fIntervals = (SkScalar*)sk_malloc_throw(sizeof(SkScalar) * count);
     fCount = count;
     for (int i = 0; i < count; i++) {
-        SkASSERT(intervals[i] >= 0);
         fIntervals[i] = intervals[i];
     }
 
@@ -38,7 +37,7 @@ SkDashPathEffect::~SkDashPathEffect() {
 
 bool SkDashPathEffect::filterPath(SkPath* dst, const SkPath& src,
                               SkStrokeRec* rec, const SkRect* cullRect) const {
-    return SkDashPath::FilterDashPath(dst, src, rec, cullRect, fIntervals, fCount,
+    return SkDashPath::InternalFilter(dst, src, rec, cullRect, fIntervals, fCount,
                                       fInitialDashLength, fInitialDashIndex, fIntervalLength);
 }
 
@@ -162,7 +161,7 @@ bool SkDashPathEffect::asPoints(PointData* results,
                                 const SkMatrix& matrix,
                                 const SkRect* cullRect) const {
     // width < 0 -> fill && width == 0 -> hairline so requiring width > 0 rules both out
-    if (fInitialDashLength < 0 || 0 >= rec.getWidth()) {
+    if (0 >= rec.getWidth()) {
         return false;
     }
 
@@ -388,13 +387,8 @@ void SkDashPathEffect::toString(SkString* str) const {
 //////////////////////////////////////////////////////////////////////////////////////////////////
 
 SkPathEffect* SkDashPathEffect::Create(const SkScalar intervals[], int count, SkScalar phase) {
-    if ((count < 2) || !SkIsAlign2(count)) {
+    if (!SkDashPath::ValidDashPath(phase, intervals, count)) {
         return nullptr;
     }
-    for (int i = 0; i < count; i++) {
-        if (intervals[i] < 0) {
-            return nullptr;
-        }
-    }
     return new SkDashPathEffect(intervals, count, phase);
 }