From edf6249e07bbb8a627aa6b376bf293be6178fc79 Mon Sep 17 00:00:00 2001
From: liyuqian <liyuqian@google.com>
Date: Thu, 27 Sep 2018 11:48:27 -0700
Subject: [PATCH] Add pushOffset to SceneBuilder (#6349)

For https://github.com/flutter/flutter/pull/21619#discussion_r220390088
---
 lib/ui/compositing.dart             | 7 +++++++
 lib/ui/compositing/scene_builder.cc | 7 +++++++
 lib/ui/compositing/scene_builder.h  | 1 +
 3 files changed, 15 insertions(+)

diff --git a/lib/ui/compositing.dart b/lib/ui/compositing.dart
index ff2cbec38..1e2af6802 100644
--- a/lib/ui/compositing.dart
+++ b/lib/ui/compositing.dart
@@ -64,6 +64,13 @@ class SceneBuilder extends NativeFieldWrapperClass2 {
   }
   void _pushTransform(Float64List matrix4) native 'SceneBuilder_pushTransform';
 
+  /// Pushes an offset operation onto the operation stack.
+  ///
+  /// This is equivalent to [pushTransform] with a matrix with only translation.
+  ///
+  /// See [pop] for details about the operation stack.
+  void pushOffset(double dx, double dy) native 'SceneBuilder_pushOffset';
+
   /// Pushes a rectangular clip operation onto the operation stack.
   ///
   /// Rasterization outside the given rectangle is discarded.
diff --git a/lib/ui/compositing/scene_builder.cc b/lib/ui/compositing/scene_builder.cc
index bf3e8c0ed..a52c6ea15 100644
--- a/lib/ui/compositing/scene_builder.cc
+++ b/lib/ui/compositing/scene_builder.cc
@@ -93,6 +93,13 @@ void SceneBuilder::pushTransform(const tonic::Float64List& matrix4) {
   PushLayer(std::move(layer), cullRect);
 }
 
+void SceneBuilder::pushOffset(double dx, double dy) {
+  SkMatrix sk_matrix = SkMatrix::MakeTrans(dx, dy);
+  auto layer = std::make_unique<flow::TransformLayer>();
+  layer->set_transform(sk_matrix);
+  PushLayer(std::move(layer), cull_rects_.top().makeOffset(-dx, -dy));
+}
+
 void SceneBuilder::pushClipRect(double left,
                                 double right,
                                 double top,
diff --git a/lib/ui/compositing/scene_builder.h b/lib/ui/compositing/scene_builder.h
index fc7bcc6a9..94fe954a8 100644
--- a/lib/ui/compositing/scene_builder.h
+++ b/lib/ui/compositing/scene_builder.h
@@ -33,6 +33,7 @@ class SceneBuilder : public RefCountedDartWrappable<SceneBuilder> {
   ~SceneBuilder() override;
 
   void pushTransform(const tonic::Float64List& matrix4);
+  void pushOffset(double dx, double dy);
   void pushClipRect(double left,
                     double right,
                     double top,
-- 
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