move getTransformTo method from RenderBox to RenderObject. (#10430)

* move getTransformTo method from RenderBox to RenderObject.

* Cleanup comment. Add slivers test.

packages/flutter/lib/src/rendering/box.dart

@@ -11,7 +11,6 @@ import 'package:flutter/gestures.dart';
 import 'package:vector_math/vector_math_64.dart';
 
 import 'debug.dart';
-import 'node.dart';
 import 'object.dart';
 
 // This class should only be used in debug builds.
@@ -1860,34 +1859,6 @@ abstract class RenderBox extends RenderObject {
     transform.translate(offset.dx, offset.dy);
   }
 
-  /// Returns a matrix that maps the local coordinate system to the coordinate
-  /// system of `ancestor`.
-  ///
-  /// If `ancestor` is null, this method returns a matrix that maps from the
-  /// local coordinate system to the coordinate system of the
-  /// [PipelineOwner.rootNode]. For the render tree owner by the
-  /// [RendererBinding] (i.e. for the main render tree displayed on the device)
-  /// this means that this method maps to the global coordinate system in
-  /// logical pixels. To get physical pixels, use [applyPaintTransform] from the
-  /// [RenderView] to further transform the coordinate.
-  Matrix4 getTransformTo(RenderObject ancestor) {
-    assert(attached);
-    if (ancestor == null) {
-      final AbstractNode rootNode = owner.rootNode;
-      if (rootNode is RenderObject)
-        ancestor = rootNode;
-    }
-    final List<RenderObject> renderers = <RenderObject>[];
-    for (RenderObject renderer = this; renderer != ancestor; renderer = renderer.parent) {
-      assert(renderer != null); // Failed to find ancestor in parent chain.
-      renderers.add(renderer);
-    }
-    final Matrix4 transform = new Matrix4.identity();
-    for (int index = renderers.length - 1; index > 0; index -= 1)
-      renderers[index].applyPaintTransform(renderers[index - 1], transform);
-    return transform;
-  }
-
   /// Convert the given point from the global coodinate system in logical pixels
   /// to the local coordinate system for this box.
   ///

packages/flutter/lib/src/rendering/object.dart

@@ -2312,6 +2312,37 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
     assert(child.parent == this);
   }
 
+  /// Applies the paint transform up the tree to `ancestor`.
+  ///
+  /// Returns a matrix that maps the local paint coordinate system to the
+  /// coordinate system of `ancestor`.
+  ///
+  /// If `ancestor` is null, this method returns a matrix that maps from the
+  /// local paint coordinate system to the coordinate system of the
+  /// [PipelineOwner.rootNode]. For the render tree owner by the
+  /// [RendererBinding] (i.e. for the main render tree displayed on the device)
+  /// this means that this method maps to the global coordinate system in
+  /// logical pixels. To get physical pixels, use [applyPaintTransform] from the
+  /// [RenderView] to further transform the coordinate.
+  Matrix4 getTransformTo(RenderObject ancestor) {
+    assert(attached);
+    if (ancestor == null) {
+      final AbstractNode rootNode = owner.rootNode;
+      if (rootNode is RenderObject)
+        ancestor = rootNode;
+    }
+    final List<RenderObject> renderers = <RenderObject>[];
+    for (RenderObject renderer = this; renderer != ancestor; renderer = renderer.parent) {
+      assert(renderer != null); // Failed to find ancestor in parent chain.
+      renderers.add(renderer);
+    }
+    final Matrix4 transform = new Matrix4.identity();
+    for (int index = renderers.length - 1; index > 0; index -= 1)
+      renderers[index].applyPaintTransform(renderers[index - 1], transform);
+    return transform;
+  }
+
+
   /// Returns a rect in this object's coordinate system that describes
   /// the approximate bounding box of the clip rect that would be
   /// applied to the given child during the paint phase, if any.

packages/flutter/test/rendering/slivers_test.dart

@@ -4,6 +4,7 @@
 
 import 'package:flutter/rendering.dart';
 import 'package:test/test.dart';
+import 'package:vector_math/vector_math_64.dart';
 
 import 'rendering_tester.dart';
 
@@ -128,6 +129,11 @@ void main() {
     expect(result.path.first.target, equals(c));
   });
 
+  Offset _getPaintOrigin(RenderObject render) {
+    final Vector3 transformed3 = render.getTransformTo(null).perspectiveTransform(new Vector3(0.0, 0.0, 0.0));
+    return new Offset(transformed3.x, transformed3.y);
+  }
+
   test('RenderViewport basic test - right', () {
     RenderBox a, b, c, d, e;
     final RenderViewport root = new RenderViewport(
@@ -146,12 +152,24 @@ void main() {
     expect(root.size.width, equals(800.0));
     expect(root.size.height, equals(600.0));
 
+    final RenderSliver sliverA = a.parent;
+    final RenderSliver sliverB = b.parent;
+    final RenderSliver sliverC = c.parent;
+    final RenderSliver sliverD = d.parent;
+    final RenderSliver sliverE = e.parent;
+
     expect(a.localToGlobal(const Offset(0.0, 0.0)), const Offset(0.0, 0.0));
     expect(b.localToGlobal(const Offset(0.0, 0.0)), const Offset(400.0, 0.0));
     expect(c.localToGlobal(const Offset(0.0, 0.0)), const Offset(800.0, 0.0));
     expect(d.localToGlobal(const Offset(0.0, 0.0)), const Offset(800.0, 0.0));
     expect(e.localToGlobal(const Offset(0.0, 0.0)), const Offset(800.0, 0.0));
 
+    expect(_getPaintOrigin(sliverA), const Offset(0.0, 0.0));
+    expect(_getPaintOrigin(sliverB), const Offset(400.0, 0.0));
+    expect(_getPaintOrigin(sliverC), const Offset(800.0, 0.0));
+    expect(_getPaintOrigin(sliverD), const Offset(800.0, 0.0));
+    expect(_getPaintOrigin(sliverE), const Offset(800.0, 0.0));
+
     root.offset = new ViewportOffset.fixed(200.0);
     pumpFrame();
     expect(a.localToGlobal(const Offset(0.0, 0.0)), const Offset(-200.0, 0.0));
@@ -160,6 +178,12 @@ void main() {
     expect(d.localToGlobal(const Offset(0.0, 0.0)), const Offset(800.0, 0.0));
     expect(e.localToGlobal(const Offset(0.0, 0.0)), const Offset(800.0, 0.0));
 
+    expect(_getPaintOrigin(sliverA), const Offset(000.0, 0.0));
+    expect(_getPaintOrigin(sliverB), const Offset(200.0, 0.0));
+    expect(_getPaintOrigin(sliverC), const Offset(600.0, 0.0));
+    expect(_getPaintOrigin(sliverD), const Offset(800.0, 0.0));
+    expect(_getPaintOrigin(sliverE), const Offset(800.0, 0.0));
+
     root.offset = new ViewportOffset.fixed(600.0);
     pumpFrame();
     expect(a.localToGlobal(const Offset(0.0, 0.0)), const Offset(-600.0, 0.0));
@@ -168,6 +192,12 @@ void main() {
     expect(d.localToGlobal(const Offset(0.0, 0.0)), const Offset(600.0, 0.0));
     expect(e.localToGlobal(const Offset(0.0, 0.0)), const Offset(800.0, 0.0));
 
+    expect(_getPaintOrigin(sliverA), const Offset(000.0, 0.0));
+    expect(_getPaintOrigin(sliverB), const Offset(000.0, 0.0));
+    expect(_getPaintOrigin(sliverC), const Offset(200.0, 0.0));
+    expect(_getPaintOrigin(sliverD), const Offset(600.0, 0.0));
+    expect(_getPaintOrigin(sliverE), const Offset(800.0, 0.0));
+
     root.offset = new ViewportOffset.fixed(900.0);
     pumpFrame();
     expect(a.localToGlobal(const Offset(0.0, 0.0)), const Offset(-900.0, 0.0));
@@ -176,6 +206,12 @@ void main() {
     expect(d.localToGlobal(const Offset(0.0, 0.0)), const Offset(300.0, 0.0));
     expect(e.localToGlobal(const Offset(0.0, 0.0)), const Offset(700.0, 0.0));
 
+    expect(_getPaintOrigin(sliverA), const Offset(000.0, 0.0));
+    expect(_getPaintOrigin(sliverB), const Offset(000.0, 0.0));
+    expect(_getPaintOrigin(sliverC), const Offset(000.0, 0.0));
+    expect(_getPaintOrigin(sliverD), const Offset(300.0, 0.0));
+    expect(_getPaintOrigin(sliverE), const Offset(700.0, 0.0));
+
     final HitTestResult result = new HitTestResult();
     root.hitTest(result, position: const Offset(150.0, 450.0));
     expect(result.path.first.target, equals(c));