cull edges that are to the right of the clip

BUG=skia:

Review URL: https://codereview.chromium.org/913503002

7 files changed, 30 insertions, 24 deletions

diff --git a/src/core/SkEdgeBuilder.cpp b/src/core/SkEdgeBuilder.cpp
index 00811203b4..6a8ea8926a 100644
--- a/src/core/SkEdgeBuilder.cpp
+++ b/src/core/SkEdgeBuilder.cpp
@@ -80,7 +80,7 @@ static void setShiftedClip(SkRect* dst, const SkIRect& src, int shift) {
 }
 
 int SkEdgeBuilder::buildPoly(const SkPath& path, const SkIRect* iclip, int shiftUp,
-                             bool clipToTheRight) {
+                             bool canCullToTheRight) {
     SkPath::Iter    iter(path, true);
     SkPoint         pts[4];
     SkPath::Verb    verb;
@@ -115,7 +115,7 @@ int SkEdgeBuilder::buildPoly(const SkPath& path, const SkIRect* iclip, int shift
                     break;
                 case SkPath::kLine_Verb: {
                     SkPoint lines[SkLineClipper::kMaxPoints];
-                    int lineCount = SkLineClipper::ClipLine(pts, clip, lines, clipToTheRight);
+                    int lineCount = SkLineClipper::ClipLine(pts, clip, lines, canCullToTheRight);
                     SkASSERT(lineCount <= SkLineClipper::kMaxClippedLineSegments);
                     for (int i = 0; i < lineCount; i++) {
                         if (edge->setLine(lines[i], lines[i + 1], shiftUp)) {
@@ -162,13 +162,13 @@ static void handle_quad(SkEdgeBuilder* builder, const SkPoint pts[3]) {
 }
 
 int SkEdgeBuilder::build(const SkPath& path, const SkIRect* iclip, int shiftUp,
-                         bool clipToTheRight) {
+                         bool canCullToTheRight) {
     fAlloc.reset();
     fList.reset();
     fShiftUp = shiftUp;
 
     if (SkPath::kLine_SegmentMask == path.getSegmentMasks()) {
-        return this->buildPoly(path, iclip, shiftUp, clipToTheRight);
+        return this->buildPoly(path, iclip, shiftUp, canCullToTheRight);
     }
 
     SkAutoConicToQuads quadder;
@@ -181,7 +181,7 @@ int SkEdgeBuilder::build(const SkPath& path, const SkIRect* iclip, int shiftUp,
     if (iclip) {
         SkRect clip;
         setShiftedClip(&clip, *iclip, shiftUp);
-        SkEdgeClipper clipper;
+        SkEdgeClipper clipper(canCullToTheRight);
 
         while ((verb = iter.next(pts, false)) != SkPath::kDone_Verb) {
             switch (verb) {
@@ -192,7 +192,7 @@ int SkEdgeBuilder::build(const SkPath& path, const SkIRect* iclip, int shiftUp,
                     break;
                 case SkPath::kLine_Verb: {
                     SkPoint lines[SkLineClipper::kMaxPoints];
-                    int lineCount = SkLineClipper::ClipLine(pts, clip, lines, clipToTheRight);
+                    int lineCount = SkLineClipper::ClipLine(pts, clip, lines, canCullToTheRight);
                     for (int i = 0; i < lineCount; i++) {
                         this->addLine(&lines[i]);
                     }
diff --git a/src/core/SkEdgeClipper.cpp b/src/core/SkEdgeClipper.cpp
index 00a1dd2494..32277bcf8e 100644
--- a/src/core/SkEdgeClipper.cpp
+++ b/src/core/SkEdgeClipper.cpp
@@ -148,7 +148,9 @@ void SkEdgeClipper::clipMonoQuad(const SkPoint srcPts[3], const SkRect& clip) {
         return;
     }
     if (pts[0].fX >= clip.fRight) {  // wholly to the right
-        this->appendVLine(clip.fRight, pts[0].fY, pts[2].fY, reverse);
+        if (!this->canCullToTheRight()) {
+            this->appendVLine(clip.fRight, pts[0].fY, pts[2].fY, reverse);
+        }
         return;
     }
 
@@ -350,7 +352,9 @@ void SkEdgeClipper::clipMonoCubic(const SkPoint src[4], const SkRect& clip) {
         return;
     }
     if (pts[0].fX >= clip.fRight) {  // wholly to the right
-        this->appendVLine(clip.fRight, pts[0].fY, pts[3].fY, reverse);
+        if (!this->canCullToTheRight()) {
+            this->appendVLine(clip.fRight, pts[0].fY, pts[3].fY, reverse);
+        }
         return;
     }
 
diff --git a/src/core/SkEdgeClipper.h b/src/core/SkEdgeClipper.h
index e16ed552ca..16887b4a32 100644
--- a/src/core/SkEdgeClipper.h
+++ b/src/core/SkEdgeClipper.h
@@ -17,14 +17,19 @@
  */
 class SkEdgeClipper {
 public:
+    SkEdgeClipper(bool canCullToTheRight) : fCanCullToTheRight(canCullToTheRight) {}
+
     bool clipQuad(const SkPoint pts[3], const SkRect& clip);
     bool clipCubic(const SkPoint pts[4], const SkRect& clip);
 
     SkPath::Verb next(SkPoint pts[]);
 
+    bool canCullToTheRight() const { return fCanCullToTheRight; }
+
 private:
     SkPoint*        fCurrPoint;
     SkPath::Verb*   fCurrVerb;
+    const bool      fCanCullToTheRight;
 
     enum {
         kMaxVerbs = 13,
diff --git a/src/core/SkLineClipper.cpp b/src/core/SkLineClipper.cpp
index 3ff8948913..4558430e33 100644
--- a/src/core/SkLineClipper.cpp
+++ b/src/core/SkLineClipper.cpp
@@ -1,10 +1,10 @@
-
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
+
 #include "SkLineClipper.h"
 
 template <typename T> T pin_unsorted(T value, T limit0, T limit1) {
@@ -172,12 +172,8 @@ static void sect_with_horizontal_test_for_pin_results() {
 }
 #endif
 
-int SkLineClipper::ClipLine(const SkPoint pts[], const SkRect& clip,
-                            SkPoint lines[], bool canClipToTheRight) {
-#if 1
-    // Disable this while we investigate layouttest failures
-    canClipToTheRight = false;
-#endif
+int SkLineClipper::ClipLine(const SkPoint pts[], const SkRect& clip, SkPoint lines[],
+                            bool canCullToTheRight) {
 
 #ifdef SK_DEBUG
     {
@@ -246,7 +242,7 @@ int SkLineClipper::ClipLine(const SkPoint pts[], const SkRect& clip,
         result = tmp;
         reverse = false;
     } else if (tmp[index0].fX >= clip.fRight) {    // wholly to the right
-        if (canClipToTheRight) {
+        if (canCullToTheRight) {
             return 0;
         }
         tmp[0].fX = tmp[1].fX = clip.fRight;
diff --git a/src/core/SkLineClipper.h b/src/core/SkLineClipper.h
index d966dbc74c..11e0a73ca2 100644
--- a/src/core/SkLineClipper.h
+++ b/src/core/SkLineClipper.h
@@ -30,7 +30,7 @@ public:
             3rd segment: lines[2]..lines[3]
      */
     static int ClipLine(const SkPoint pts[2], const SkRect& clip,
-                        SkPoint lines[kMaxPoints], bool canClipToTheRight);
+                        SkPoint lines[kMaxPoints], bool canCullToTheRight);
 
     /*  Intersect the line segment against the rect. If there is a non-empty
         resulting segment, return true and set dst[] to that segment. If not,
@@ -40,8 +40,7 @@ public:
         segments on the sides to show where the line extended beyond the
         left or right sides. IntersectLine does not.
      */
-    static bool IntersectLine(const SkPoint src[2], const SkRect& clip,
-                              SkPoint dst[2]);
+    static bool IntersectLine(const SkPoint src[2], const SkRect& clip, SkPoint dst[2]);
 };
 
 #endif
diff --git a/src/core/SkScan_Path.cpp b/src/core/SkScan_Path.cpp
index 4142d1092f..fd04609c21 100644
--- a/src/core/SkScan_Path.cpp
+++ b/src/core/SkScan_Path.cpp
@@ -431,12 +431,14 @@ void sk_fill_path(const SkPath& path, const SkIRect* clipRect, SkBlitter* blitte
     SkEdgeBuilder   builder;
 
     // If we're convex, then we need both edges, even the right edge is past the clip
-    const bool cullToTheRight = !path.isConvex();
+    const bool canCullToTheRight = !path.isConvex();
+
+    int count = builder.build(path, clipRect, shiftEdgesUp, canCullToTheRight);
+    SkASSERT(count >= 0);
 
-    int count = builder.build(path, clipRect, shiftEdgesUp, cullToTheRight);
     SkEdge**    list = builder.edgeList();
 
-    if (count < 2) {
+    if (0 == count) {
         if (path.isInverseFillType()) {
             /*
              *  Since we are in inverse-fill, our caller has already drawn above
@@ -458,7 +460,6 @@ void sk_fill_path(const SkPath& path, const SkIRect* clipRect, SkBlitter* blitte
                                   rect.height() << shiftEdgesUp);
             }
         }
-
         return;
     }
 
@@ -498,6 +499,7 @@ void sk_fill_path(const SkPath& path, const SkIRect* clipRect, SkBlitter* blitte
     }
 
     if (path.isConvex() && (NULL == proc)) {
+        SkASSERT(count >= 2);   // convex walker does not handle missing right edges
         walk_convex_edges(&headEdge, path.getFillType(), blitter, start_y, stop_y, NULL);
     } else {
         int rightEdge;
diff --git a/tests/ClipperTest.cpp b/tests/ClipperTest.cpp
index 00b62293b2..8ebd9b479f 100644
--- a/tests/ClipperTest.cpp
+++ b/tests/ClipperTest.cpp
@@ -48,7 +48,7 @@ static void test_hairclipping(skiatest::Reporter* reporter) {
 }
 
 static void test_edgeclipper() {
-    SkEdgeClipper clipper;
+    SkEdgeClipper clipper(false);
 
     const SkPoint pts[] = {
         { 3.0995476e+010f,  42.929779f },