Ignore rounding error between clip_layer_length_ and scroll_layer_length_

cc/layers/scrollbar_layer_unittest.cc

 // Copyright 2012 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 <stddef.h>
 
 #include <unordered_map>
 
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "cc/animation/animation_host.h"
 #include "cc/input/scrollbar_animation_controller.h"
 #include "cc/layers/append_quads_data.h"
 #include "cc/layers/painted_overlay_scrollbar_layer.h"
 #include "cc/layers/painted_scrollbar_layer.h"
 #include "cc/layers/painted_scrollbar_layer_impl.h"
 #include "cc/layers/scrollbar_layer_interface.h"
 #include "cc/layers/solid_color_scrollbar_layer.h"
 #include "cc/layers/solid_color_scrollbar_layer_impl.h"
 #include "cc/quads/solid_color_draw_quad.h"
 #include "cc/resources/ui_resource_manager.h"
 #include "cc/test/fake_impl_task_runner_provider.h"
 #include "cc/test/fake_layer_tree_host.h"
 #include "cc/test/fake_layer_tree_host_client.h"
 #include "cc/test/fake_layer_tree_host_impl.h"
 #include "cc/test/fake_painted_scrollbar_layer.h"
 #include "cc/test/fake_scrollbar.h"
 #include "cc/test/geometry_test_utils.h"
+#include "cc/test/layer_test_common.h"
 #include "cc/test/layer_tree_test.h"
 #include "cc/test/mock_occlusion_tracker.h"
 #include "cc/test/stub_layer_tree_host_single_thread_client.h"
 #include "cc/test/test_context_provider.h"
 #include "cc/test/test_task_graph_runner.h"
 #include "cc/test/test_web_graphics_context_3d.h"
 #include "cc/trees/effect_node.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/layer_tree_impl.h"
 #include "cc/trees/occlusion_tracker.h"
@@ skipping 723 matching lines @@
   layer_tree_host_->UpdateLayers();
   host_impl->CreatePendingTree();
   layer_tree_host_->CommitAndCreatePendingTree();
   host_impl->ActivateSyncTree();
   EffectNode* node =
       host_impl->active_tree()->property_trees()->effect_tree.Node(
           scrollbar_layer->effect_tree_index());
   EXPECT_EQ(node->opacity, 1.f);
 }
 
+TEST_F(ScrollbarLayerTest, SubPixelCanScrollOrientation) {
+  gfx::Size viewport_size(100, 100);
+
+  LayerTestCommon::LayerImplTest impl;
+
+  LayerImpl* clip_layer = impl.AddChildToRoot<LayerImpl>();
+  LayerImpl* scroll_layer = impl.AddChild<LayerImpl>(clip_layer);
+
+  scroll_layer->SetScrollClipLayer(clip_layer->id());
+
+  const int kTrackStart = 0;
+  const int kThumbThickness = 10;
+  const bool kIsLeftSideVerticalScrollbar = false;
+  const bool kIsOverlayScrollbar = false;
+
+  SolidColorScrollbarLayerImpl* scrollbar_layer =
+      impl.AddChild<SolidColorScrollbarLayerImpl>(
+          scroll_layer, HORIZONTAL, kThumbThickness, kTrackStart,
+          kIsLeftSideVerticalScrollbar, kIsOverlayScrollbar);
+
+  scrollbar_layer->SetScrollInfo(scroll_layer->id(),
+                                 scrollbar_layer->element_id());
+  clip_layer->SetBounds(gfx::Size(100, 100));
+  scroll_layer->SetBounds(gfx::Size(100, 100));
+
+  impl.CalcDrawProps(viewport_size);
+
+  // Fake device scale.
+  impl.host_impl()->active_tree()->SetDeviceScaleFactor(3);
+
+  // Fake clip layer length to scrollbar to mock rounding error.
+  scrollbar_layer->SetClipLayerLength(99.99f);
+
+  EXPECT_FALSE(scrollbar_layer->CanScrollOrientation());
+
+  // Fake clip layer length to scrollbar to 1 device pixel shorter than scroll
+  // layer.
+  scrollbar_layer->SetClipLayerLength(99.65f);
+
+  EXPECT_TRUE(scrollbar_layer->CanScrollOrientation());
+}
+
 class ScrollbarLayerSolidColorThumbTest : public testing::Test {
  public:
   ScrollbarLayerSolidColorThumbTest() {
     LayerTreeSettings layer_tree_settings;
     host_impl_.reset(new FakeLayerTreeHostImpl(
         layer_tree_settings, &task_runner_provider_, &task_graph_runner_));
 
     const int kThumbThickness = 3;
     const int kTrackStart = 0;
     const bool kIsLeftSideVerticalScrollbar = false;
@@ skipping 467 matching lines @@
   TestScale(gfx::Rect(1240, 0, 15, 1333), 2.7754839f);
   TestScale(gfx::Rect(1240, 0, 15, 677), 2.46677136f);
 
   // Horizontal Scrollbars.
   TestScale(gfx::Rect(0, 1240, 1333, 15), 2.7754839f);
   TestScale(gfx::Rect(0, 1240, 677, 15), 2.46677136f);
 }
 
 }  // namespace
 }  // namespace cc