[WIP] Add Context to SkDrawLooper.

SkDrawLooper carries some state during draws. This CL extracts this state into
a separate class Context, which is then passed by the users of SkDrawLooper
into the appropriate methods.
This is a step towards making SkDrawLooper immutable.

BUG=skia:2141
R=scroggo@google.com, reed@google.com, sugoi@google.com

Author: dominikg@chromium.org

Review URL: https://codereview.chromium.org/155513012

git-svn-id: http://skia.googlecode.com/svn/trunk@13760 2bbb7eff-a529-9590-31e7-b0007b416f81

2 files changed, 27 insertions, 19 deletions

diff --git a/src/effects/SkBlurDrawLooper.cpp b/src/effects/SkBlurDrawLooper.cpp
index 3a5c697371..0bbc184049 100644
--- a/src/effects/SkBlurDrawLooper.cpp
+++ b/src/effects/SkBlurDrawLooper.cpp
@@ -33,7 +33,6 @@ void SkBlurDrawLooper::init(SkScalar sigma, SkScalar dx, SkScalar dy,
     fDy = dy;
     fBlurColor = color;
     fBlurFlags = flags;
-    fState = kDone;
 
     SkASSERT(flags <= kAll_BlurFlag);
     if (sigma > 0) {
@@ -90,11 +89,16 @@ void SkBlurDrawLooper::flatten(SkWriteBuffer& buffer) const {
     buffer.writeUInt(fBlurFlags);
 }
 
-void SkBlurDrawLooper::init(SkCanvas*) {
-    fState = kBeforeEdge;
+SkDrawLooper::Context* SkBlurDrawLooper::createContext(SkCanvas*, void* storage) const {
+    return SkNEW_PLACEMENT_ARGS(storage, BlurDrawLooperContext, (this));
 }
 
-bool SkBlurDrawLooper::next(SkCanvas* canvas, SkPaint* paint) {
+SkBlurDrawLooper::BlurDrawLooperContext::BlurDrawLooperContext(
+        const SkBlurDrawLooper* looper)
+    : fLooper(looper), fState(SkBlurDrawLooper::kBeforeEdge) {}
+
+bool SkBlurDrawLooper::BlurDrawLooperContext::next(SkCanvas* canvas,
+                                                   SkPaint* paint) {
     switch (fState) {
         case kBeforeEdge:
             // we do nothing if a maskfilter is already installed
@@ -104,23 +108,23 @@ bool SkBlurDrawLooper::next(SkCanvas* canvas, SkPaint* paint) {
             }
 #ifdef SK_BUILD_FOR_ANDROID
             SkColor blurColor;
-            blurColor = fBlurColor;
+            blurColor = fLooper->fBlurColor;
             if (SkColorGetA(blurColor) == 255) {
                 blurColor = SkColorSetA(blurColor, paint->getAlpha());
             }
             paint->setColor(blurColor);
 #else
-            paint->setColor(fBlurColor);
+            paint->setColor(fLooper->fBlurColor);
 #endif
-            paint->setMaskFilter(fBlur);
-            paint->setColorFilter(fColorFilter);
+            paint->setMaskFilter(fLooper->fBlur);
+            paint->setColorFilter(fLooper->fColorFilter);
             canvas->save(SkCanvas::kMatrix_SaveFlag);
-            if (fBlurFlags & kIgnoreTransform_BlurFlag) {
+            if (fLooper->fBlurFlags & kIgnoreTransform_BlurFlag) {
                 SkMatrix transform(canvas->getTotalMatrix());
-                transform.postTranslate(fDx, fDy);
+                transform.postTranslate(fLooper->fDx, fLooper->fDy);
                 canvas->setMatrix(transform);
             } else {
-                canvas->translate(fDx, fDy);
+                canvas->translate(fLooper->fDx, fLooper->fDy);
             }
             fState = kAfterEdge;
             return true;
diff --git a/src/effects/SkLayerDrawLooper.cpp b/src/effects/SkLayerDrawLooper.cpp
index cfe673db92..6d31c23a06 100644
--- a/src/effects/SkLayerDrawLooper.cpp
+++ b/src/effects/SkLayerDrawLooper.cpp
@@ -24,8 +24,7 @@ SkLayerDrawLooper::LayerInfo::LayerInfo() {
 SkLayerDrawLooper::SkLayerDrawLooper()
         : fRecs(NULL),
           fTopRec(NULL),
-          fCount(0),
-          fCurrRec(NULL) {
+          fCount(0) {
 }
 
 SkLayerDrawLooper::~SkLayerDrawLooper() {
@@ -75,9 +74,9 @@ SkPaint* SkLayerDrawLooper::addLayerOnTop(const LayerInfo& info) {
     return &rec->fPaint;
 }
 
-void SkLayerDrawLooper::init(SkCanvas* canvas) {
-    fCurrRec = fRecs;
+SkLayerDrawLooper::Context* SkLayerDrawLooper::createContext(SkCanvas* canvas, void* storage) const {
     canvas->save(SkCanvas::kMatrix_SaveFlag);
+    return SkNEW_PLACEMENT_ARGS(storage, LayerDrawLooperContext, (this));
 }
 
 static SkColor xferColor(SkColor src, SkColor dst, SkXfermode::Mode mode) {
@@ -98,8 +97,8 @@ static SkColor xferColor(SkColor src, SkColor dst, SkXfermode::Mode mode) {
 // Even with kEntirePaint_Bits, we always ensure that the master paint's
 // text-encoding is respected, since that controls how we interpret the
 // text/length parameters of a draw[Pos]Text call.
-void SkLayerDrawLooper::ApplyInfo(SkPaint* dst, const SkPaint& src,
-                                  const LayerInfo& info) {
+void SkLayerDrawLooper::LayerDrawLooperContext::ApplyInfo(
+        SkPaint* dst, const SkPaint& src, const LayerInfo& info) {
 
     dst->setColor(xferColor(src.getColor(), dst->getColor(), info.fColorMode));
 
@@ -167,7 +166,11 @@ static void postTranslate(SkCanvas* canvas, SkScalar dx, SkScalar dy) {
     canvas->setMatrix(m);
 }
 
-bool SkLayerDrawLooper::next(SkCanvas* canvas, SkPaint* paint) {
+SkLayerDrawLooper::LayerDrawLooperContext::LayerDrawLooperContext(
+        const SkLayerDrawLooper* looper) : fCurrRec(looper->fRecs) {}
+
+bool SkLayerDrawLooper::LayerDrawLooperContext::next(SkCanvas* canvas,
+                                                     SkPaint* paint) {
     canvas->restore();
     if (NULL == fCurrRec) {
         return false;
@@ -180,7 +183,8 @@ bool SkLayerDrawLooper::next(SkCanvas* canvas, SkPaint* paint) {
         postTranslate(canvas, fCurrRec->fInfo.fOffset.fX,
                       fCurrRec->fInfo.fOffset.fY);
     } else {
-        canvas->translate(fCurrRec->fInfo.fOffset.fX, fCurrRec->fInfo.fOffset.fY);
+        canvas->translate(fCurrRec->fInfo.fOffset.fX,
+                          fCurrRec->fInfo.fOffset.fY);
     }
     fCurrRec = fCurrRec->fNext;