cc: Do not allow gesture-scrolling 'overflow[-{x|y}]:hidden' layers.

cc/trees/layer_tree_host_impl_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/trees/layer_tree_host_impl.h"
 
 #include <cmath>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 741 matching lines @@
       vertical_scrollbar.get());
 
   // Trying to scroll with a vertical scrollbar will succeed.
   EXPECT_TRUE(host_impl_->ScrollVerticallyByPage(
       gfx::Point(), SCROLL_FORWARD));
   EXPECT_FLOAT_EQ(875.f, host_impl_->RootScrollLayer()->ScrollDelta().y());
   EXPECT_TRUE(host_impl_->ScrollVerticallyByPage(
       gfx::Point(), SCROLL_BACKWARD));
 }
 
+TEST_F(LayerTreeHostImplTest, ScrollWithUserUnscrollableLayers) {
+  LayerImpl* scroll_layer = SetupScrollAndContentsLayers(gfx::Size(200, 200));
+  host_impl_->SetViewportSize(gfx::Size(100, 100));
+
+  gfx::Size overflow_size(400, 400);
+  ASSERT_EQ(1, scroll_layer->children().size());
+  LayerImpl* overflow = scroll_layer->children()[0];
+  overflow->SetBounds(overflow_size);
+  overflow->SetContentBounds(overflow_size);
+  overflow->SetScrollable(true);
+  overflow->SetMaxScrollOffset(gfx::Vector2d(overflow_size.width(),
+                                             overflow_size.height()));
+  overflow->SetScrollOffset(gfx::Vector2d());
+  overflow->SetPosition(gfx::PointF());
+  overflow->SetAnchorPoint(gfx::PointF());
+
+  InitializeRendererAndDrawFrame();
+  gfx::Point scroll_position(10, 10);
+
+  EXPECT_EQ(InputHandler::ScrollStarted,
+            host_impl_->ScrollBegin(scroll_position, InputHandler::Wheel));
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(), scroll_layer->TotalScrollOffset());
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(), overflow->TotalScrollOffset());
+
+  gfx::Vector2dF scroll_delta(10, 10);
+  host_impl_->ScrollBy(scroll_position, scroll_delta);
+  host_impl_->ScrollEnd();
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(), scroll_layer->TotalScrollOffset());
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(10, 10), overflow->TotalScrollOffset());
+
+  overflow->SetUserScrollable(false, true);

[jamesr, 2013/10/21 22:36:34]

callsites like this are really hard to read - what does this mean?

i think exposing the pair:
set_user_scrollable_horizontal(bool)
set_user_scrollable_vertical(bool)

while slightly more verbose would be worth it in increased readability

[sadrul, 2013/10/21 22:39:03]

Should this be done for the blink change in
https://codereview.chromium.org/33413002/ too? Or just from WebLayerImpl
onwards?

[sadrul, 2013/10/21 23:11:17]

Done (replaced LayerImpl::SetUserScrollable() with
LayerImpl::set_user_scrollable_*())

+
+  EXPECT_EQ(InputHandler::ScrollStarted,
+            host_impl_->ScrollBegin(scroll_position, InputHandler::Wheel));
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(), scroll_layer->TotalScrollOffset());
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(10, 10), overflow->TotalScrollOffset());
+
+  host_impl_->ScrollBy(scroll_position, scroll_delta);
+  host_impl_->ScrollEnd();
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(10, 0), scroll_layer->TotalScrollOffset());
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(10, 20), overflow->TotalScrollOffset());
+
+  overflow->SetUserScrollable(false, false);
+
+  EXPECT_EQ(InputHandler::ScrollStarted,
+            host_impl_->ScrollBegin(scroll_position, InputHandler::Wheel));
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(10, 0), scroll_layer->TotalScrollOffset());
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(10, 20), overflow->TotalScrollOffset());
+
+  host_impl_->ScrollBy(scroll_position, scroll_delta);
+  host_impl_->ScrollEnd();
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(20, 10), scroll_layer->TotalScrollOffset());
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(10, 20), overflow->TotalScrollOffset());
+}
+
 TEST_F(LayerTreeHostImplTest,
        ClearRootRenderSurfaceAndHitTestTouchHandlerRegion) {
   SetupScrollAndContentsLayers(gfx::Size(100, 100));
   host_impl_->SetViewportSize(gfx::Size(50, 50));
   InitializeRendererAndDrawFrame();
 
   // We should be able to hit test for touch event handlers even if the root
   // layer loses its render surface after the most recent render.
   host_impl_->active_tree()->root_layer()->ClearRenderSurface();
   host_impl_->active_tree()->set_needs_update_draw_properties();
@@ skipping 4657 matching lines @@
     // The root should have scrolled.
     ASSERT_EQ(2u, scroll_info->scrolls.size());
     ExpectContains(*scroll_info.get(),
                    host_impl_->active_tree()->root_layer()->id(),
                    gfx::Vector2d(0, 10));
   }
 }
 
 }  // namespace
 }  // namespace cc