add optional cull-rect to patheffects, so they can do less work if their results
lie outside of the current clip-bounds (the cull rect).
Review URL: https://codereview.appspot.com/7206044

git-svn-id: http://skia.googlecode.com/svn/trunk@7378 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkDraw.cpp b/src/core/SkDraw.cpp
index 45a023b..87f117b 100644
--- a/src/core/SkDraw.cpp
+++ b/src/core/SkDraw.cpp
@@ -122,6 +122,23 @@
     memcpy(this, &src, sizeof(*this));
 }
 
+bool SkDraw::computeConservativeLocalClipBounds(SkRect* localBounds) const {
+    if (fRC->isEmpty()) {
+        return false;
+    }
+
+    SkMatrix inverse;
+    if (!fMatrix->invert(&inverse)) {
+        return false;
+    }
+
+    SkIRect devBounds = fRC->getBounds();
+    // outset to have slop for antialasing and hairlines
+    devBounds.outset(1, 1);
+    inverse.mapRect(localBounds, SkRect::Make(devBounds));
+    return true;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 typedef void (*BitmapXferProc)(void* pixels, size_t bytes, uint32_t data);
@@ -668,7 +685,10 @@
                     path.moveTo(pts[0]);
                     path.lineTo(pts[1]);
 
-                    if (paint.getPathEffect()->asPoints(&pointData, path, rec, *fMatrix)) {
+                    SkRect cullRect = SkRect::Make(fRC->getBounds());
+                    
+                    if (paint.getPathEffect()->asPoints(&pointData, path, rec,
+                                                        *fMatrix, &cullRect)) {
                         // 'asPoints' managed to find some fast path
 
                         SkPaint newP(paint);
@@ -1057,7 +1077,12 @@
     }
 
     if (paint->getPathEffect() || paint->getStyle() != SkPaint::kFill_Style) {
-        doFill = paint->getFillPath(*pathPtr, &tmpPath);
+        SkRect cullRect;
+        const SkRect* cullRectPtr = NULL;
+        if (this->computeConservativeLocalClipBounds(&cullRect)) {
+            cullRectPtr = &cullRect;
+        }
+        doFill = paint->getFillPath(*pathPtr, &tmpPath, cullRectPtr);
         pathPtr = &tmpPath;
     }
 
@@ -2765,3 +2790,4 @@
 
     return true;
 }
+
diff --git a/src/core/SkPaint.cpp b/src/core/SkPaint.cpp
index 8f14ba8..71a68ef 100644
--- a/src/core/SkPaint.cpp
+++ b/src/core/SkPaint.cpp
@@ -2145,13 +2145,14 @@
 
 ///////////////////////////////////////////////////////////////////////////////
 
-bool SkPaint::getFillPath(const SkPath& src, SkPath* dst) const {
+bool SkPaint::getFillPath(const SkPath& src, SkPath* dst,
+                          const SkRect* cullRect) const {
     SkStrokeRec rec(*this);
 
     const SkPath* srcPtr = &src;
     SkPath tmpPath;
 
-    if (fPathEffect && fPathEffect->filterPath(&tmpPath, src, &rec)) {
+    if (fPathEffect && fPathEffect->filterPath(&tmpPath, src, &rec, cullRect)) {
         srcPtr = &tmpPath;
     }
 
diff --git a/src/core/SkPathEffect.cpp b/src/core/SkPathEffect.cpp
index ebbfd6d..38332a4 100644
--- a/src/core/SkPathEffect.cpp
+++ b/src/core/SkPathEffect.cpp
@@ -19,7 +19,7 @@
 }
 
 bool SkPathEffect::asPoints(PointData* results, const SkPath& src,
-                            const SkStrokeRec&, const SkMatrix&) const {
+                    const SkStrokeRec&, const SkMatrix&, const SkRect*) const {
     return false;
 }
 
@@ -56,7 +56,7 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 bool SkComposePathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                     SkStrokeRec* rec) const {
+                             SkStrokeRec* rec, const SkRect* cullRect) const {
     // we may have failed to unflatten these, so we have to check
     if (!fPE0 || !fPE1) {
         return false;
@@ -65,16 +65,18 @@
     SkPath          tmp;
     const SkPath*   ptr = &src;
 
-    if (fPE1->filterPath(&tmp, src, rec)) {
+    if (fPE1->filterPath(&tmp, src, rec, cullRect)) {
         ptr = &tmp;
     }
-    return fPE0->filterPath(dst, *ptr, rec);
+    return fPE0->filterPath(dst, *ptr, rec, cullRect);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 bool SkSumPathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                 SkStrokeRec* rec) const {
+                             SkStrokeRec* rec, const SkRect* cullRect) const {
     // use bit-or so that we always call both, even if the first one succeeds
-    return fPE0->filterPath(dst, src, rec) | fPE1->filterPath(dst, src, rec);
+    return fPE0->filterPath(dst, src, rec, cullRect) |
+           fPE1->filterPath(dst, src, rec, cullRect);
 }
+
diff --git a/src/core/SkScalerContext.cpp b/src/core/SkScalerContext.cpp
index c16fa76..c35c0db 100644
--- a/src/core/SkScalerContext.cpp
+++ b/src/core/SkScalerContext.cpp
@@ -638,7 +638,7 @@
 
         if (fPathEffect) {
             SkPath effectPath;
-            if (fPathEffect->filterPath(&effectPath, localPath, &rec)) {
+            if (fPathEffect->filterPath(&effectPath, localPath, &rec, NULL)) {
                 localPath.swap(effectPath);
             }
         }
diff --git a/src/effects/Sk1DPathEffect.cpp b/src/effects/Sk1DPathEffect.cpp
index 3ef050c..10a68b9 100644
--- a/src/effects/Sk1DPathEffect.cpp
+++ b/src/effects/Sk1DPathEffect.cpp
@@ -12,7 +12,7 @@
 #include "SkPathMeasure.h"
 
 bool Sk1DPathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                SkStrokeRec*) const {
+                                SkStrokeRec*, const SkRect*) const {
     SkPathMeasure   meas(src, false);
     do {
         SkScalar    length = meas.getLength();
@@ -69,10 +69,10 @@
 }
 
 bool SkPath1DPathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                    SkStrokeRec* rec) const {
+                            SkStrokeRec* rec, const SkRect* cullRect) const {
     if (fAdvance > 0) {
         rec->setFillStyle();
-        return this->INHERITED::filterPath(dst, src, rec);
+        return this->INHERITED::filterPath(dst, src, rec, cullRect);
     }
     return false;
 }
diff --git a/src/effects/Sk2DPathEffect.cpp b/src/effects/Sk2DPathEffect.cpp
index a4ebe74..dc15f07 100644
--- a/src/effects/Sk2DPathEffect.cpp
+++ b/src/effects/Sk2DPathEffect.cpp
@@ -17,7 +17,7 @@
 }
 
 bool Sk2DPathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                SkStrokeRec*) const {
+                                SkStrokeRec*, const SkRect*) const {
     if (!fMatrixIsInvertible) {
         return false;
     }
@@ -80,8 +80,8 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 bool SkLine2DPathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                    SkStrokeRec* rec) const {
-    if (this->INHERITED::filterPath(dst, src, rec)) {
+                            SkStrokeRec* rec, const SkRect* cullRect) const {
+    if (this->INHERITED::filterPath(dst, src, rec, cullRect)) {
         rec->setStrokeStyle(fWidth);
         return true;
     }
diff --git a/src/effects/SkCornerPathEffect.cpp b/src/effects/SkCornerPathEffect.cpp
index b63045d..1cf797a 100644
--- a/src/effects/SkCornerPathEffect.cpp
+++ b/src/effects/SkCornerPathEffect.cpp
@@ -31,7 +31,7 @@
 }
 
 bool SkCornerPathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                    SkStrokeRec*) const {
+                                    SkStrokeRec*, const SkRect*) const {
     if (0 == fRadius) {
         return false;
     }
diff --git a/src/effects/SkDashPathEffect.cpp b/src/effects/SkDashPathEffect.cpp
index ef10ca5..d1ce526 100644
--- a/src/effects/SkDashPathEffect.cpp
+++ b/src/effects/SkDashPathEffect.cpp
@@ -88,10 +88,81 @@
     sk_free(fIntervals);
 }
 
+static void outset_for_stroke(SkRect* rect, const SkStrokeRec& rec) {
+    SkScalar radius = SkScalarHalf(rec.getWidth());
+    if (0 == radius) {
+        radius = SK_Scalar1;    // hairlines
+    }
+    if (SkPaint::kMiter_Join == rec.getJoin()) {
+        radius = SkScalarMul(radius, rec.getMiter());
+    }
+    rect->outset(radius, radius);
+}
+
+// Only handles lines for now. If returns true, dstPath is the new (smaller)
+// path. If returns false, then dstPath parameter is ignored.
+static bool cull_path(const SkPath& srcPath, const SkStrokeRec& rec,
+                      const SkRect* cullRect, SkScalar intervalLength,
+                      SkPath* dstPath) {
+    if (NULL == cullRect) {
+        return false;
+    }
+
+    SkPoint pts[2];
+    if (!srcPath.isLine(pts)) {
+        return false;
+    }
+
+    SkRect bounds = *cullRect;
+    outset_for_stroke(&bounds, rec);
+
+    SkScalar dx = pts[1].x() - pts[0].x();
+    SkScalar dy = pts[1].y() - pts[0].y();
+    
+    // just do horizontal lines for now (lazy)
+    if (dy) {
+        return false;
+    }
+
+    SkScalar minX = pts[0].fX;
+    SkScalar maxX = pts[1].fX;
+    
+    if (maxX < bounds.fLeft || minX > bounds.fRight) {
+        return false;
+    }
+    
+    if (dx < 0) {
+        SkTSwap(minX, maxX);
+    }
+
+    // Now we actually perform the chop, removing the excess to the left and
+    // right of the bounds (keeping our new line "in phase" with the dash,
+    // hence the (mod intervalLength).
+
+    if (minX < bounds.fLeft) {
+        minX = bounds.fLeft - SkScalarMod(bounds.fLeft - minX,
+                                          intervalLength);
+    }
+    if (maxX > bounds.fRight) {
+        maxX = bounds.fRight + SkScalarMod(maxX - bounds.fRight,
+                                           intervalLength);
+    }
+    
+    SkASSERT(maxX > minX);
+    if (dx < 0) {
+        SkTSwap(minX, maxX);
+    }
+    pts[0].fX = minX;
+    pts[1].fX = maxX;
+    
+    dstPath->moveTo(pts[0]);
+    dstPath->lineTo(pts[1]);
+    return true;
+}
+
 class SpecialLineRec {
 public:
     bool init(const SkPath& src, SkPath* dst, SkStrokeRec* rec,
-              SkScalar pathLength,
               int intervalCount, SkScalar intervalLength) {
         if (rec->isHairlineStyle() || !src.isLine(fPts)) {
             return false;
@@ -102,6 +173,8 @@
             return false;
         }
 
+        SkScalar pathLength = SkPoint::Distance(fPts[0], fPts[1]);
+
         fTangent = fPts[1] - fPts[0];
         if (fTangent.isZero()) {
             return false;
@@ -156,19 +229,25 @@
 };
 
 bool SkDashPathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                  SkStrokeRec* rec) const {
+                              SkStrokeRec* rec, const SkRect* cullRect) const {
     // we do nothing if the src wants to be filled, or if our dashlength is 0
     if (rec->isFillStyle() || fInitialDashLength < 0) {
         return false;
     }
 
-    SkPathMeasure   meas(src, false);
     const SkScalar* intervals = fIntervals;
     SkScalar        dashCount = 0;
 
+    SkPath cullPathStorage;
+    const SkPath* srcPtr = &src;
+    if (cull_path(src, *rec, cullRect, fIntervalLength, &cullPathStorage)) {
+        srcPtr = &cullPathStorage;
+    }
+    
     SpecialLineRec lineRec;
-    const bool specialLine = lineRec.init(src, dst, rec, meas.getLength(),
-                                          fCount >> 1, fIntervalLength);
+    bool specialLine = lineRec.init(src, dst, rec, fCount >> 1, fIntervalLength);
+
+    SkPathMeasure   meas(*srcPtr, false);
 
     do {
         bool        skipFirstSegment = meas.isClosed();
@@ -256,7 +335,8 @@
 bool SkDashPathEffect::asPoints(PointData* results,
                                 const SkPath& src,
                                 const SkStrokeRec& rec,
-                                const SkMatrix& matrix) const {
+                                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()) {
         return false;
diff --git a/src/effects/SkDiscretePathEffect.cpp b/src/effects/SkDiscretePathEffect.cpp
index a936be9..2c95208 100644
--- a/src/effects/SkDiscretePathEffect.cpp
+++ b/src/effects/SkDiscretePathEffect.cpp
@@ -26,7 +26,7 @@
 }
 
 bool SkDiscretePathEffect::filterPath(SkPath* dst, const SkPath& src,
-                                      SkStrokeRec* rec) const {
+                                      SkStrokeRec* rec, const SkRect*) const {
     bool doFill = rec->isFillStyle();
 
     SkPathMeasure   meas(src, doFill);
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 827fc52..3e20e3b 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -972,7 +972,9 @@
 
     SkStrokeRec stroke(paint);
     SkPathEffect* pathEffect = paint.getPathEffect();
-    if (pathEffect && pathEffect->filterPath(&effectPath, *pathPtr, &stroke)) {
+    const SkRect* cullRect = NULL;  // TODO: what is our bounds?
+    if (pathEffect && pathEffect->filterPath(&effectPath, *pathPtr, &stroke,
+                                             cullRect)) {
         pathPtr = &effectPath;
     }