Move code in isPaintOpaque from SkDeferredCanvas.cpp to SkPaintPriv

The purpose of this code move is to make it re-usable in order to implement
occlusion culling optimizations in SkPicture similar to what we have now
in SkDeferredCanvas.

BUG=https://code.google.com/p/chromium/issues/detail?id=164530
Review URL: https://codereview.appspot.com/7196046

git-svn-id: http://skia.googlecode.com/svn/trunk@7361 2bbb7eff-a529-9590-31e7-b0007b416f81

3 files changed, 105 insertions, 70 deletions

diff --git a/src/core/SkPaintPriv.cpp b/src/core/SkPaintPriv.cpp
new file mode 100644
index 0000000000..ce05389019
--- /dev/null
+++ b/src/core/SkPaintPriv.cpp
@@ -0,0 +1,78 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkPaintPriv.h"
+
+#include "SkBitmap.h"
+#include "SkColorFilter.h"
+#include "SkPaint.h"
+#include "SkShader.h"
+
+bool isPaintOpaque(const SkPaint* paint,
+                   const SkBitmap* bmpReplacesShader) {
+    // TODO: SkXfermode should have a virtual isOpaque method, which would
+    // make it possible to test modes that do not have a Coeff representation.
+
+    if (!paint) {
+        return bmpReplacesShader ? bmpReplacesShader->isOpaque() : true;
+    }
+
+    SkXfermode::Coeff srcCoeff, dstCoeff;
+    if (SkXfermode::AsCoeff(paint->getXfermode(), &srcCoeff, &dstCoeff)){
+        if (SkXfermode::kDA_Coeff == srcCoeff || SkXfermode::kDC_Coeff == srcCoeff ||
+            SkXfermode::kIDA_Coeff == srcCoeff || SkXfermode::kIDC_Coeff == srcCoeff) {
+            return false;
+        }
+        switch (dstCoeff) {
+        case SkXfermode::kZero_Coeff:
+            return true;
+        case SkXfermode::kISA_Coeff:
+            if (paint->getAlpha() != 255) {
+                break;
+            }
+            if (bmpReplacesShader) {
+                if (!bmpReplacesShader->isOpaque()) {
+                    break;
+                }
+            } else if (paint->getShader() && !paint->getShader()->isOpaque()) {
+                break;
+            }
+            if (paint->getColorFilter() &&
+                ((paint->getColorFilter()->getFlags() &
+                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
+                break;
+            }
+            return true;
+        case SkXfermode::kSA_Coeff:
+            if (paint->getAlpha() != 0) {
+                break;
+            }
+            if (paint->getColorFilter() &&
+                ((paint->getColorFilter()->getFlags() &
+                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
+                break;
+            }
+            return true;
+        case SkXfermode::kSC_Coeff:
+            if (paint->getColor() != 0) { // all components must be 0
+                break;
+            }
+            if (bmpReplacesShader || paint->getShader()) {
+                break;
+            }
+            if (paint->getColorFilter() && (
+                (paint->getColorFilter()->getFlags() &
+                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
+                break;
+            }
+            return true;
+        default:
+            break;
+        }
+    }
+    return false;
+}
diff --git a/src/core/SkPaintPriv.h b/src/core/SkPaintPriv.h
new file mode 100644
index 0000000000..38c9063e56
--- /dev/null
+++ b/src/core/SkPaintPriv.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkPaintPriv_DEFINED
+#define SkPaintPriv_DEFINED
+
+class SkBitmap;
+class SkPaint;
+
+#include "SkTypes.h"
+/** Returns true if draw calls that use the paint will completely occlude
+    canvas contents that are covered by the draw.
+    @param paint The paint to be analyzed, NULL is equivalent to
+        the default paint.
+    @param bmpReplacesShader a bitmap to be used in place of the paint's
+        shader.
+    @return true if paint is opaque
+*/
+bool isPaintOpaque(const SkPaint* paint,
+                   const SkBitmap* bmpReplacesShader = NULL);
+#endif
diff --git a/src/utils/SkDeferredCanvas.cpp b/src/utils/SkDeferredCanvas.cpp
index 3c6dc2c7ef..5119729447 100644
--- a/src/utils/SkDeferredCanvas.cpp
+++ b/src/utils/SkDeferredCanvas.cpp
@@ -1,6 +1,6 @@
 
 /*
- * Copyright 2012 Google Inc.
+ * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
@@ -14,6 +14,7 @@
 #include "SkDrawFilter.h"
 #include "SkGPipe.h"
 #include "SkPaint.h"
+#include "SkPaintPriv.h"
 #include "SkRRect.h"
 #include "SkShader.h"
 
@@ -54,75 +55,6 @@ bool shouldDrawImmediately(const SkBitmap* bitmap, const SkPaint* paint,
 }
 }
 
-namespace {
-
-bool isPaintOpaque(const SkPaint* paint,
-                   const SkBitmap* bmpReplacesShader = NULL) {
-    // TODO: SkXfermode should have a virtual isOpaque method, which would
-    // make it possible to test modes that do not have a Coeff representation.
-
-    if (!paint) {
-        return bmpReplacesShader ? bmpReplacesShader->isOpaque() : true;
-    }
-
-    SkXfermode::Coeff srcCoeff, dstCoeff;
-    if (SkXfermode::AsCoeff(paint->getXfermode(), &srcCoeff, &dstCoeff)){
-        if (SkXfermode::kDA_Coeff == srcCoeff || SkXfermode::kDC_Coeff == srcCoeff ||
-            SkXfermode::kIDA_Coeff == srcCoeff || SkXfermode::kIDC_Coeff == srcCoeff) {
-            return false;
-        }
-        switch (dstCoeff) {
-        case SkXfermode::kZero_Coeff:
-            return true;
-        case SkXfermode::kISA_Coeff:
-            if (paint->getAlpha() != 255) {
-                break;
-            }
-            if (bmpReplacesShader) {
-                if (!bmpReplacesShader->isOpaque()) {
-                    break;
-                }
-            } else if (paint->getShader() && !paint->getShader()->isOpaque()) {
-                break;
-            }
-            if (paint->getColorFilter() &&
-                ((paint->getColorFilter()->getFlags() &
-                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
-                break;
-            }
-            return true;
-        case SkXfermode::kSA_Coeff:
-            if (paint->getAlpha() != 0) {
-                break;
-            }
-            if (paint->getColorFilter() &&
-                ((paint->getColorFilter()->getFlags() &
-                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
-                break;
-            }
-            return true;
-        case SkXfermode::kSC_Coeff:
-            if (paint->getColor() != 0) { // all components must be 0
-                break;
-            }
-            if (bmpReplacesShader || paint->getShader()) {
-                break;
-            }
-            if (paint->getColorFilter() && (
-                (paint->getColorFilter()->getFlags() &
-                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
-                break;
-            }
-            return true;
-        default:
-            break;
-        }
-    }
-    return false;
-}
-
-} // unnamed namespace
-
 //-----------------------------------------------------------------------------
 // DeferredPipeController
 //-----------------------------------------------------------------------------