Move canvas->surface association to the device subclasses

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 7b881d60a298e31005aefd375d6428b55df6b70f..fda57984677eced76ba3cfeda87a30da99438aaf 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -16,6 +16,7 @@
 #include "GrContext.h"
 #include "GrBitmapTextContext.h"
 #include "GrDistanceFieldTextContext.h"
+#include "GrGpuResourcePriv.h"
 #include "GrLayerHoister.h"
 #include "GrRecordReplaceDraw.h"
 #include "GrStrokeInfo.h"
@@ -45,6 +46,7 @@
 #include "SkXfermode.h"
 #include "SkErrorInternals.h"
 
+
 #if SK_SUPPORT_GPU
 
 enum { kDefaultImageFilterCacheSize = 32 * 1024 * 1024 };
@@ -149,6 +151,7 @@ static SkSurfaceProps copy_or_default_props(const SkSurfaceProps* props) {
 SkGpuDevice::SkGpuDevice(GrRenderTarget* rt, const SkSurfaceProps* props, unsigned flags)
     : INHERITED(surfaceprops_to_deviceprops(props))
     , fSurfaceProps(copy_or_default_props(props))
+    , fSurface(NULL)
 {
     fDrawProcs = NULL;
 
@@ -233,12 +236,17 @@ SkGpuDevice::~SkGpuDevice() {
         fContext->setClip(NULL);
     }
 
-    fRenderTarget->unref();
     fContext->unref();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
+void SkGpuDevice::discard() {
+    if (fSurface) {
+        fSurface->aboutToDraw(SkSurface::kDiscard_ContentChangeMode);
+    }
+}
+
 bool SkGpuDevice::onReadPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
                                int x, int y) {
     DO_DEFERRED_CLEAR();
@@ -297,6 +305,9 @@ void SkGpuDevice::onDetachFromCanvas() {
 // and not the state from some other canvas/device
 void SkGpuDevice::prepareDraw(const SkDraw& draw) {
     SkASSERT(fClipData.fClipStack);
+    if (fSurface) {
+        fSurface->aboutToDraw(SkSurface::kRetain_ContentChangeMode);
+    }
 
     fContext->setRenderTarget(fRenderTarget);
 
@@ -322,16 +333,33 @@ void SkGpuDevice::clearAll() {
     fNeedClear = false;
 }
 
-void SkGpuDevice::swapRenderTarget(GrRenderTarget* newRenderTarget) {
+void SkGpuDevice::detachBackendRenderTarget(bool retainContent) {
     SkASSERT(!fNeedClear);
     if (fContext->getRenderTarget() == fRenderTarget) {
         fContext->setRenderTarget(NULL);
     }
-    SkRefCnt_SafeAssign(fRenderTarget, newRenderTarget);
-    SkASSERT(newRenderTarget->surfacePriv().info() == fLegacyBitmap.info());
-    SkPixelRef* pr = SkNEW_ARGS(SkGrPixelRef, (newRenderTarget->surfacePriv().info(),
-                                               newRenderTarget));
-    fLegacyBitmap.setPixelRef(pr)->unref();
+
+    GrRenderTarget* oldRT = fRenderTarget;
+    SkSurface::Budgeted budgeted = oldRT->resourcePriv().isBudgeted() ? SkSurface::kYes_Budgeted :
+            SkSurface::kNo_Budgeted;
+
+    GrRenderTarget* newRT = CreateRenderTarget(oldRT->getContext(), budgeted, this->imageInfo(),
+                                               oldRT->numSamples());
+    if (newRT) {
+        if (retainContent && !oldRT->wasDestroyed()) {
+            oldRT->getContext()->copySurface(newRT, oldRT);
+        }
+
+        if (fRenderTarget != newRT) {
+            fRenderTarget->unref();
+            fRenderTarget = newRT;
+        }
+
+        SkASSERT(newRT->surfacePriv().info() == fLegacyBitmap.info());
+        SkPixelRef* pr = SkNEW_ARGS(SkGrPixelRef, (newRT->surfacePriv().info(),
+                                                   newRT));
+        fLegacyBitmap.setPixelRef(pr)->unref();
+    }
 }
 
 ///////////////////////////////////////////////////////////////////////////////