Align physical pixels of scrolled layers

cc/layer_tree_host_common_unittest.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layer_tree_host_common.h"
 
 #include "cc/content_layer.h"
 #include "cc/content_layer_client.h"
 #include "cc/heads_up_display_layer_impl.h"
 #include "cc/layer.h"
@@ skipping 240 matching lines @@
     // Case 7: Verify that position pre-multiplies the layer transform.
     //         The current implementation of calculateDrawProperties does this implicitly, but it is
     //         still worth testing to detect accidental regressions.
     expectedResult = positionTransform * translationToAnchor * layerTransform * inverse(translationToAnchor);
     setLayerPropertiesForTesting(layer.get(), layerTransform, identityMatrix, gfx::PointF(0.5, 0), gfx::PointF(0, 1.2f), gfx::Size(10, 12), false);
     executeCalculateDrawProperties(root.get());
     EXPECT_TRANSFORMATION_MATRIX_EQ(expectedResult, layer->drawTransform());
     EXPECT_TRANSFORMATION_MATRIX_EQ(expectedResult, layer->screenSpaceTransform());
 }
 
+TEST(LayerTreeHostCommonTest, verifyTransformsAboutScrollOffset)
+{
+    const gfx::Vector2d kScrollOffset(50, 100);
+    const gfx::Vector2dF kScrollDelta(2.34, 5.67);
+    const gfx::PointF kScrollLayerPosition(-kScrollOffset.x(), -kScrollOffset.y());
+    const float kPageScale = 0.888;
+    const float kDeviceScale = 1.666;
+
+    FakeImplProxy proxy;
+    FakeLayerTreeHostImpl hostImpl(&proxy);
+
+    gfx::Transform identityMatrix;
+    scoped_ptr<LayerImpl> sublayerScopedPtr(LayerImpl::create(hostImpl.activeTree(), 1));
+    LayerImpl* sublayer = sublayerScopedPtr.get();
+    sublayer->setContentsScale(kPageScale * kDeviceScale, kPageScale * kDeviceScale);
+    setLayerPropertiesForTesting(sublayer, identityMatrix, identityMatrix, gfx::Point(0, 0), gfx::PointF(0, 0), gfx::Size(500, 500), false);
+
+    scoped_ptr<LayerImpl> scrollLayer(LayerImpl::create(hostImpl.activeTree(), 2));
+    setLayerPropertiesForTesting(scrollLayer.get(), identityMatrix, identityMatrix, gfx::PointF(0, 0), gfx::PointF(0, 0), gfx::Size(10, 20), false);
+    scrollLayer->setScrollable(true);
+    scrollLayer->setScrollOffset(kScrollOffset);
+    scrollLayer->setScrollDelta(kScrollDelta);
+    scrollLayer->setPosition(kScrollLayerPosition);
+    gfx::Transform implTransform;
+    implTransform.Scale(kPageScale, kPageScale);
+    scrollLayer->setImplTransform(implTransform);
+    scrollLayer->addChild(sublayerScopedPtr.Pass());
+
+    scoped_ptr<LayerImpl> root(LayerImpl::create(hostImpl.activeTree(), 3));
+    setLayerPropertiesForTesting(root.get(), identityMatrix, identityMatrix, gfx::PointF(0, 0), gfx::PointF(0, 0), gfx::Size(3, 4), false);
+    root->addChild(scrollLayer.Pass());
+
+    executeCalculateDrawProperties(root.get(), kDeviceScale, kPageScale);
+    gfx::Transform expectedTransform = identityMatrix;
+    gfx::PointF subLayerScreenPosition = kScrollLayerPosition - kScrollDelta;
+    subLayerScreenPosition.Scale(kPageScale * kDeviceScale);
+    expectedTransform.Translate(round(subLayerScreenPosition.x()), round(subLayerScreenPosition.y()));
+    EXPECT_TRANSFORMATION_MATRIX_EQ(expectedTransform, sublayer->drawTransform());
+    EXPECT_TRANSFORMATION_MATRIX_EQ(expectedTransform, sublayer->screenSpaceTransform());
+}
+
 TEST(LayerTreeHostCommonTest, verifyTransformsForSimpleHierarchy)
 {
     gfx::Transform identityMatrix;
     scoped_refptr<Layer> root = Layer::create();
     scoped_refptr<Layer> parent = Layer::create();
     scoped_refptr<Layer> child = Layer::create();
     scoped_refptr<Layer> grandChild = Layer::create();
     root->addChild(parent);
     parent->addChild(child);
     child->addChild(grandChild);
@@ skipping 4819 matching lines @@
     EXPECT_EQ(m_canUseLCDText, m_grandChild->canUseLCDText());
 }
 
 INSTANTIATE_TEST_CASE_P(LayerTreeHostCommonTest,
                         LCDTextTest,
                         testing::Combine(testing::Bool(),
                                          testing::Bool()));
 
 }  // namespace
 }  // namespace cc