Swap render target instead of creating a new gpu device for surface copy-on-write

src/image/SkSurface_Gpu.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkSurface_Gpu.h"
 
 #include "GrGpuResourcePriv.h"
 #include "SkCanvas.h"
 #include "SkGpuDevice.h"
 #include "SkImage_Base.h"
 #include "SkImagePriv.h"
 #include "SkSurface_Base.h"
 
 #if SK_SUPPORT_GPU
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkSurface_Gpu::SkSurface_Gpu(SkGpuDevice* device)
     : INHERITED(device->width(), device->height(), &device->surfaceProps())
     , fDevice(SkRef(device)) {
 }
 
 SkSurface_Gpu::~SkSurface_Gpu() {
-    SkSafeUnref(fDevice);
+    fDevice->unref();
 }
 
 SkCanvas* SkSurface_Gpu::onNewCanvas() {
     SkCanvas::InitFlags flags = SkCanvas::kDefault_InitFlags;
     // When we think this works...
 //    flags |= SkCanvas::kConservativeRasterClip_InitFlag;
 
     return SkNEW_ARGS(SkCanvas, (fDevice, &this->props(), flags));
 }
 
@@ skipping 14 matching lines @@
         as_IB(image)->initWithProps(this->props());
     }
     return image;
 }
 
 void SkSurface_Gpu::onDraw(SkCanvas* canvas, SkScalar x, SkScalar y,
                               const SkPaint* paint) {
     canvas->drawBitmap(fDevice->accessBitmap(false), x, y, paint);
 }
 
-// Create a new SkGpuDevice and, if necessary, copy the contents of the old
-// device into it. Note that this flushes the SkGpuDevice but
+// Create a new render target and, if necessary, copy the contents of the old
+// render target into it. Note that this flushes the SkGpuDevice but
 // doesn't force an OpenGL flush.
 void SkSurface_Gpu::onCopyOnWrite(ContentChangeMode mode) {
     GrRenderTarget* rt = fDevice->accessRenderTarget();
     // are we sharing our render target with the image? Note this call should never create a new
     // image because onCopyOnWrite is only called when there is a cached image.
     SkImage* image = this->getCachedImage(kNo_Budgeted);
     SkASSERT(image);
     if (rt->asTexture() == SkTextureImageGetTexture(image)) {
         GrRenderTarget* oldRT = this->fDevice->accessRenderTarget();
         SkSurface::Budgeted budgeted = oldRT->resourcePriv().isBudgeted() ? kYes_Budgeted :
-                                                                            kNo_Budgeted;
-        SkAutoTUnref<SkGpuDevice> newDevice(
-            SkGpuDevice::Create(oldRT->getContext(), budgeted, fDevice->imageInfo(),
-                                oldRT->numSamples(), &this->props(), 0));
-        if (kRetain_ContentChangeMode == mode && !oldRT->wasDestroyed() && newDevice) {
-            oldRT->getContext()->copySurface(newDevice->accessRenderTarget(), oldRT);
+                kNo_Budgeted;
+        SkAutoTUnref<GrRenderTarget> newRT(
+            SkGpuDevice::CreateRenderTarget(oldRT->getContext(), budgeted, fDevice->imageInfo(),
+                                            oldRT->numSamples()));
+
+        if (kRetain_ContentChangeMode == mode && !oldRT->wasDestroyed() && newRT) {
+            oldRT->getContext()->copySurface(newRT, oldRT);
         }
 
         SkASSERT(this->getCachedCanvas());
         SkASSERT(this->getCachedCanvas()->getDevice() == fDevice);
 
-        this->getCachedCanvas()->setRootDevice(newDevice);
-        SkRefCnt_SafeAssign(fDevice, newDevice.get());
+        this->fDevice->swapRenderTarget(newRT);
 
         SkTextureImageApplyBudgetedDecision(image);
     } else if (kDiscard_ContentChangeMode == mode) {
         this->SkSurface_Gpu::onDiscard();
     }
 }
 
 void SkSurface_Gpu::onDiscard() {
     fDevice->accessRenderTarget()->discard();
 }
 
+
 ///////////////////////////////////////////////////////////////////////////////
 
 SkSurface* SkSurface::NewRenderTargetDirect(GrRenderTarget* target, const SkSurfaceProps* props) {
     SkAutoTUnref<SkGpuDevice> device(SkGpuDevice::Create(target, props));
     if (!device) {
         return NULL;
     }
     return SkNEW_ARGS(SkSurface_Gpu, (device));
 }
 
 SkSurface* SkSurface::NewRenderTarget(GrContext* ctx, Budgeted budgeted, const SkImageInfo& info,
                                       int sampleCount, const SkSurfaceProps* props) {
-    SkAutoTUnref<SkGpuDevice> device(SkGpuDevice::Create(ctx, budgeted, info, sampleCount, props,
-                                                         SkGpuDevice::kNeedClear_Flag));
-    if (!device) {
+    SkAutoTUnref<GrRenderTarget> rt(SkGpuDevice::CreateRenderTarget(ctx, budgeted, info,

[bsalomon, 2015/02/18 14:29:37]

It seems a tad unfortunate to require this two step creation for the initial
SkGpuDevice.

[Kimmo Kinnunen, 2015/02/18 15:06:46]

Yeah.. Once the texture creation succeeds, the SkGpuDevice creation can not
fail. I'd prefer constructing the SkGpuDevice inside SkSurface_Gpu constructor,
since surface constructor is where the device is created. I did not do this,
since it would imply SkGpuDevice::Create should be removed. I did not remove it,
because I was afraid of changing the API would cause the patch review/merge to
stall.

[Kimmo Kinnunen, 2015/02/19 15:52:18]

Done.

+                                                                    sampleCount));
+    if (NULL == rt) {
+        return NULL;
+    }
+    SkAutoTUnref<SkGpuDevice> device(SkGpuDevice::Create(rt, props, SkGpuDevice::kNeedClear_Flag));
+    if (NULL == device) {
         return NULL;
     }
     return SkNEW_ARGS(SkSurface_Gpu, (device));
 }
 
 #endif