cc: Return whether any layer was scrolled from InputHandlerClient::scrollBy.

BUG=none

Review URL: https://codereview.chromium.org/11365238

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@167721 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 47 insertions, 8 deletions

diff --git a/cc/input_handler.h b/cc/input_handler.h
index 6898c1f..0a2a542 100644
--- a/cc/input_handler.h
+++ b/cc/input_handler.h
@@ -41,9 +41,11 @@ public:
     // should be in viewport (logical pixel) coordinates. Otherwise they are in
     // scrolling layer's (logical pixel) space. If there is no room to move the
     // layer in the requested direction, its first ancestor layer that can be
-    // scrolled will be moved instead. Should only be called if scrollBegin()
-    // returned ScrollStarted.
-    virtual void scrollBy(gfx::Point, gfx::Vector2d) = 0;
+    // scrolled will be moved instead. If no layer can be moved in the requested
+    // direction at all, then false is returned. If any layer is moved, then
+    // true is returned.
+    // Should only be called if scrollBegin() returned ScrollStarted.
+    virtual bool scrollBy(const gfx::Point&, const gfx::Vector2d&) = 0;
 
     // Stop scrolling the selected layer. Should only be called if scrollBegin()
     // returned ScrollStarted.
diff --git a/cc/layer_tree_host_impl.cc b/cc/layer_tree_host_impl.cc
index 32366d3..21207b1 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -1145,11 +1145,12 @@ static gfx::Vector2dF scrollLayerWithLocalDelta(LayerImpl& layerImpl, gfx::Vecto
     return layerImpl.scrollDelta() - previousDelta;
 }
 
-void LayerTreeHostImpl::scrollBy(gfx::Point viewportPoint, gfx::Vector2d scrollDelta)
+bool LayerTreeHostImpl::scrollBy(const gfx::Point& viewportPoint,
+                                 const gfx::Vector2d& scrollDelta)
 {
     TRACE_EVENT0("cc", "LayerTreeHostImpl::scrollBy");
     if (!m_currentlyScrollingLayerImpl)
-        return;
+        return false;
 
     gfx::Vector2dF pendingDelta = scrollDelta;
 
@@ -1190,7 +1191,9 @@ void LayerTreeHostImpl::scrollBy(gfx::Point viewportPoint, gfx::Vector2d scrollD
     if (!scrollDelta.IsZero() && gfx::ToFlooredVector2d(pendingDelta).IsZero()) {
         m_client->setNeedsCommitOnImplThread();
         m_client->setNeedsRedrawOnImplThread();
+        return true;
     }
+    return false;
 }
 
 void LayerTreeHostImpl::clearCurrentlyScrollingLayer()
diff --git a/cc/layer_tree_host_impl.h b/cc/layer_tree_host_impl.h
index 10020c8..8e59c62 100644
--- a/cc/layer_tree_host_impl.h
+++ b/cc/layer_tree_host_impl.h
@@ -111,7 +111,7 @@ public:
 
     // InputHandlerClient implementation
     virtual InputHandlerClient::ScrollStatus scrollBegin(gfx::Point, InputHandlerClient::ScrollInputType) OVERRIDE;
-    virtual void scrollBy(gfx::Point, gfx::Vector2d) OVERRIDE;
+    virtual bool scrollBy(const gfx::Point&, const gfx::Vector2d&) OVERRIDE;
     virtual void scrollEnd() OVERRIDE;
     virtual void pinchGestureBegin() OVERRIDE;
     virtual void pinchGestureUpdate(float, gfx::Point) OVERRIDE;
diff --git a/cc/layer_tree_host_impl_unittest.cc b/cc/layer_tree_host_impl_unittest.cc
index ce71ced..9ac8970 100644
--- a/cc/layer_tree_host_impl_unittest.cc
+++ b/cc/layer_tree_host_impl_unittest.cc
@@ -479,6 +479,35 @@ TEST_P(LayerTreeHostImplTest, nonFastScrollableRegionWithOffset)
     EXPECT_EQ(m_hostImpl->scrollBegin(gfx::Point(10, 10), InputHandlerClient::Wheel), InputHandlerClient::ScrollOnMainThread);
 }
 
+TEST_P(LayerTreeHostImplTest, scrollByReturnsCorrectValue)
+{
+    setupScrollAndContentsLayers(gfx::Size(200, 200));
+    m_hostImpl->setViewportSize(gfx::Size(100, 100), gfx::Size(100, 100));
+
+    initializeRendererAndDrawFrame();
+
+    EXPECT_EQ(InputHandlerClient::ScrollStarted,
+        m_hostImpl->scrollBegin(gfx::Point(0, 0), InputHandlerClient::Gesture));
+
+    // Trying to scroll to the left/top will not succeed.
+    EXPECT_FALSE(m_hostImpl->scrollBy(gfx::Point(), gfx::Vector2d(-10, 0)));
+    EXPECT_FALSE(m_hostImpl->scrollBy(gfx::Point(), gfx::Vector2d(0, -10)));
+    EXPECT_FALSE(m_hostImpl->scrollBy(gfx::Point(), gfx::Vector2d(-10, -10)));
+
+    // Scrolling to the right/bottom will succeed.
+    EXPECT_TRUE(m_hostImpl->scrollBy(gfx::Point(), gfx::Vector2d(10, 0)));
+    EXPECT_TRUE(m_hostImpl->scrollBy(gfx::Point(), gfx::Vector2d(0, 10)));
+    EXPECT_TRUE(m_hostImpl->scrollBy(gfx::Point(), gfx::Vector2d(10, 10)));
+
+    // Scrolling to left/top will now succeed.
+    EXPECT_TRUE(m_hostImpl->scrollBy(gfx::Point(), gfx::Vector2d(-10, 0)));
+    EXPECT_TRUE(m_hostImpl->scrollBy(gfx::Point(), gfx::Vector2d(0, -10)));
+    EXPECT_TRUE(m_hostImpl->scrollBy(gfx::Point(), gfx::Vector2d(-10, -10)));
+
+    // Trying to scroll more than the available space will also succeed.
+    EXPECT_TRUE(m_hostImpl->scrollBy(gfx::Point(), gfx::Vector2d(5000, 5000)));
+}
+
 TEST_P(LayerTreeHostImplTest, maxScrollOffsetChangedByDeviceScaleFactor)
 {
     setupScrollAndContentsLayers(gfx::Size(100, 100));
diff --git a/webkit/compositor_bindings/web_to_ccinput_handler_adapter.cc b/webkit/compositor_bindings/web_to_ccinput_handler_adapter.cc
index 9d68cf3..30d105a 100644
--- a/webkit/compositor_bindings/web_to_ccinput_handler_adapter.cc
+++ b/webkit/compositor_bindings/web_to_ccinput_handler_adapter.cc
@@ -47,9 +47,14 @@ public:
         return static_cast<WebInputHandlerClient::ScrollStatus>(m_client->scrollBegin(point, static_cast<cc::InputHandlerClient::ScrollInputType>(type)));
     }
 
-    virtual void scrollBy(WebPoint point, WebSize offset) OVERRIDE
+    virtual void scrollBy(WebPoint point, WebSize offset)
     {
-        m_client->scrollBy(point, offset);
+        scrollByIfPossible(point, offset);
+    }
+
+    virtual bool scrollByIfPossible(WebPoint point, WebSize offset)
+    {
+      return m_client->scrollBy(point, offset);
     }
 
     virtual void scrollEnd() OVERRIDE