change SkCanvasStack to take ownership of its subcanvases

Inspired by https://bugs.chromium.org/p/chromium/issues/detail?id=663959

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4799

Change-Id: I69f7ac73386bb7ca96778e2fec4cb2757b982a52
Reviewed-on: https://skia-review.googlesource.com/4799
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/src/utils/SkCanvasStack.cpp b/src/utils/SkCanvasStack.cpp
index 58607d7d29..8e4bd37540 100644
--- a/src/utils/SkCanvasStack.cpp
+++ b/src/utils/SkCanvasStack.cpp
@@ -13,18 +13,19 @@ SkCanvasStack::~SkCanvasStack() {
     this->removeAll();
 }
 
-void SkCanvasStack::pushCanvas(SkCanvas* canvas, const SkIPoint& origin) {
+void SkCanvasStack::pushCanvas(std::unique_ptr<SkCanvas> canvas, const SkIPoint& origin) {
     if (canvas) {
         // compute the bounds of this canvas
         const SkIRect canvasBounds = SkIRect::MakeSize(canvas->getDeviceSize());
 
         // push the canvas onto the stack
-        this->INHERITED::addCanvas(canvas);
+        this->INHERITED::addCanvas(canvas.get());
 
         // push the canvas data onto the stack
         CanvasData* data = &fCanvasData.push_back();
         data->origin = origin;
         data->requiredClip.setRect(canvasBounds);
+        data->ownedCanvas = std::move(canvas);
 
         // subtract this region from the canvas objects already on the stack.
         // This ensures they do not draw into the space occupied by the layers
@@ -41,8 +42,8 @@ void SkCanvasStack::pushCanvas(SkCanvas* canvas, const SkIPoint& origin) {
 }
 
 void SkCanvasStack::removeAll() {
+    this->INHERITED::removeAll();   // call the baseclass *before* we actually delete the canvases
     fCanvasData.reset();
-    this->INHERITED::removeAll();
 }
 
 /**