Initialize OpacityLayer's matrix to identity (#8467) (#8548)

chingjun · web-flow · commit 4737fc5cd89b · 2019-04-11T13:17:59.000-07:00
Should have flutter/flutter#30586 fixed once the engine rolls.
diff --git a/flow/layers/opacity_layer.cc b/flow/layers/opacity_layer.cc
@@ -20,6 +20,13 @@ void OpacityLayer::EnsureSingleChild() {
   }
 
   auto new_child = std::make_shared<flow::TransformLayer>();
+
+  // Be careful: SkMatrix's default constructor doesn't initialize the matrix to
+  // identity. Hence we have to explicitly call SkMatrix::setIdentity.
+  SkMatrix identity;
+  identity.setIdentity();
+
+  new_child->set_transform(identity);
   for (auto& child : layers()) {
     new_child->Add(child);
   }
diff --git a/flow/layers/transform_layer.h b/flow/layers/transform_layer.h
@@ -9,6 +9,8 @@
 
 namespace flow {
 
+// Be careful that SkMatrix's default constructor doesn't initialize the matrix
+// at all. Hence |set_transform| must be called with an initialized SkMatrix.
 class TransformLayer : public ContainerLayer {
  public:
   TransformLayer();

Original file line number	Diff line number	Diff line change
`@@ -20,6 +20,13 @@ void OpacityLayer::EnsureSingleChild() {`
`20`	`20`	`}`
`21`	`21`
`22`	`22`	`auto new_child = std::make_shared<flow::TransformLayer>();`
	`23`	`+`
	`24`	`+ // Be careful: SkMatrix's default constructor doesn't initialize the matrix to`
	`25`	`+ // identity. Hence we have to explicitly call SkMatrix::setIdentity.`
	`26`	`+ SkMatrix identity;`
	`27`	`+ identity.setIdentity();`
	`28`	`+`
	`29`	`+ new_child->set_transform(identity);`
`23`	`30`	`for (auto& child : layers()) {`
`24`	`31`	`new_child->Add(child);`
`25`	`32`	`}`