Implement SkBaseDevice snapshot support

src/core/SkBitmapDevice.cpp

Index: src/core/SkBitmapDevice.cpp
diff --git a/src/core/SkBitmapDevice.cpp b/src/core/SkBitmapDevice.cpp
index 2d2fe9e6d4049a8802f27302059a0b866604cf54..a09821e941b8c25d0009703c1c991e40c43ac838 100644
--- a/src/core/SkBitmapDevice.cpp
+++ b/src/core/SkBitmapDevice.cpp
@@ -9,6 +9,7 @@
 #include "SkConfig8888.h"
 #include "SkDeviceProperties.h"
 #include "SkDraw.h"
+#include "SkImagePriv.h"
 #include "SkImage_Base.h"
 #include "SkRasterClip.h"
 #include "SkShader.h"
@@ -70,6 +71,9 @@ SkBitmapDevice::SkBitmapDevice(const SkBitmap& bitmap, const SkDeviceProperties&
     SkASSERT(valid_for_bitmap_device(bitmap.info(), NULL));
 }
 
+SkBitmapDevice::~SkBitmapDevice() {
+}
+
 SkBitmapDevice* SkBitmapDevice::Create(const SkImageInfo& origInfo,
                                        const SkDeviceProperties* props) {
     SkAlphaType newAT = origInfo.alphaType();
@@ -104,11 +108,15 @@ SkImageInfo SkBitmapDevice::imageInfo() const {
     return fBitmap.info();
 }
 
-void SkBitmapDevice::replaceBitmapBackendForRasterSurface(const SkBitmap& bm) {
-    SkASSERT(bm.width() == fBitmap.width());
-    SkASSERT(bm.height() == fBitmap.height());
-    fBitmap = bm;   // intent is to use bm's pixelRef (and rowbytes/config)
-    fBitmap.lockPixels();
+void SkBitmapDevice::deepCopyBackendIfNeeded() {
+    if (NULL != fSnapshot) {
+        if (!fSnapshot->unique()) {
+            SkBitmap prev(fBitmap);
+            prev.deepCopyTo(&fBitmap);
+            fBitmap.lockPixels();
+        }
+        fSnapshot.reset(NULL);
+    }
 }
 
 SkBaseDevice* SkBitmapDevice::onCreateDevice(const CreateInfo& cinfo, const SkPaint*) {
@@ -129,11 +137,13 @@ void SkBitmapDevice::unlockPixels() {
 }
 
 const SkBitmap& SkBitmapDevice::onAccessBitmap() {
+    this->deepCopyBackendIfNeeded();
     return fBitmap;
 }
 
 void* SkBitmapDevice::onAccessPixels(SkImageInfo* info, size_t* rowBytes) {
     if (fBitmap.getPixels()) {
+        this->deepCopyBackendIfNeeded();
         *info = fBitmap.info();
         *rowBytes = fBitmap.rowBytes();
         return fBitmap.getPixels();
@@ -351,7 +361,14 @@ void SkBitmapDevice::drawVertices(const SkDraw& draw, SkCanvas::VertexMode vmode
 
 void SkBitmapDevice::drawDevice(const SkDraw& draw, SkBaseDevice* device,
                                 int x, int y, const SkPaint& paint) {
-    const SkBitmap& src = device->accessBitmap(false);
+    SkAutoTUnref<SkImage> image(device->newImageSnapshot());
+    if (NULL == image) {
+        return;
+    }
+    SkBitmap src;
+    if (!as_IB(image.get())->getROPixels(&src)) {
+        return;
+    }
     draw.drawSprite(src, x, y, paint);
 }
 
@@ -359,6 +376,27 @@ SkSurface* SkBitmapDevice::newSurface(const SkImageInfo& info, const SkSurfacePr
     return SkSurface::NewRaster(info, &props);
 }
 
+void SkBitmapDevice::discard() {
+    if (NULL != fSnapshot) {
+        if (!fSnapshot->unique()) {
+            fBitmap.setPixelRef(NULL);
+            fBitmap.allocPixels();
+        }
+        fSnapshot.reset(NULL);
+    }
+}
+
+SkImage* SkBitmapDevice::newImageSnapshot() {
+    if (NULL == fSnapshot) {
+        fSnapshot.reset(this->onNewImageSnapshot());
+    }
+    return SkSafeRef(fSnapshot.get());
+}
+
+SkImage* SkBitmapDevice::onNewImageSnapshot() {
+    return SkNewImageFromBitmap(fBitmap, NULL);
+}
+
 const void* SkBitmapDevice::peekPixels(SkImageInfo* info, size_t* rowBytes) {
     const SkImageInfo bmInfo = fBitmap.info();
     if (fBitmap.getPixels() && (kUnknown_SkColorType != bmInfo.colorType())) {