Scrollbar ThumbLength is not updated when window size is changed.

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 "base/containers/hash_tables.h"
 #include "cc/animation/scrollbar_animation_controller.h"
 #include "cc/layers/append_quads_data.h"
 #include "cc/layers/painted_scrollbar_layer.h"
 #include "cc/layers/painted_scrollbar_layer_impl.h"
 #include "cc/layers/scrollbar_layer_interface.h"
@@ skipping 174 matching lines @@
 #define UPDATE_AND_EXTRACT_LAYER_POINTERS()                         \
   do {                                                              \
     scrollbar_layer->UpdateThumbAndTrackGeometry();                 \
     root_clip_layer_impl = host->CommitAndCreateLayerImplTree();    \
     root_layer_impl = root_clip_layer_impl->children()[0];          \
     scrollbar_layer_impl = static_cast<PaintedScrollbarLayerImpl*>( \
         root_layer_impl->children()[1]);                            \
     scrollbar_layer_impl->ScrollbarParametersDidChange();           \
   } while (false)
 
+TEST(ScrollbarLayerTest, UpdatePropertiesOfScrollBarWhenThumbRemoved) {
+  scoped_ptr<FakeLayerTreeHost> host = FakeLayerTreeHost::Create();
+  scoped_refptr<Layer> root_clip_layer = Layer::Create();
+  scoped_refptr<Layer> root_layer = Layer::Create();
+  scoped_refptr<Layer> content_layer = Layer::Create();
+  scoped_refptr<FakePaintedScrollbarLayer> scrollbar_layer =
+      FakePaintedScrollbarLayer::Create(false, true, root_layer->id());
+
+  root_layer->SetScrollClipLayerId(root_clip_layer->id());
+  // Give the root-clip a size that will result in MaxScrollOffset = (80, 0).
+  root_clip_layer->SetBounds(gfx::Size(20, 50));
+  root_layer->SetBounds(gfx::Size(100, 50));
+  content_layer->SetBounds(gfx::Size(100, 50));
+
+  host->SetRootLayer(root_clip_layer);
+  root_clip_layer->AddChild(root_layer);
+  root_layer->AddChild(content_layer);
+  root_layer->AddChild(scrollbar_layer);
+
+  root_layer->SetScrollOffset(gfx::Vector2d(0, 0));
+  scrollbar_layer->SetBounds(gfx::Size(70, 10));
+  scrollbar_layer->SetScrollLayer(root_layer->id());
+  scrollbar_layer->SetClipLayer(root_clip_layer->id());
+  scrollbar_layer->fake_scrollbar()->set_location(gfx::Point(20, 10));
+  scrollbar_layer->fake_scrollbar()->set_track_rect(gfx::Rect(30, 10, 50, 10));
+  scrollbar_layer->fake_scrollbar()->set_thumb_thickness(10);
+  scrollbar_layer->fake_scrollbar()->set_thumb_length(4);
+
+  scrollbar_layer->UpdateThumbAndTrackGeometry();
+  LayerImpl* root_clip_layer_impl = NULL;
+  LayerImpl* root_layer_impl = NULL;
+  PaintedScrollbarLayerImpl* scrollbar_layer_impl = NULL;
+
+  UPDATE_AND_EXTRACT_LAYER_POINTERS();
+  EXPECT_EQ(gfx::Rect(10, 0, 4, 10).ToString(),
+            scrollbar_layer_impl->ComputeThumbQuadRect().ToString());
+
+  scrollbar_layer->fake_scrollbar()->set_thumb_thickness(0);

[danakj, 2014/09/03 17:20:51]

Hm, I guess this is building the assumption that the real Scrollbar will do the
same thing when thumb is false. I don't feel super comfortable with that
assumption since we can't test it.

So, how about remove these 2 set_thumb_thickness/length calls here. And in the
scrollbar class if(has_thumb_) { use the values from Scrollbar } else { use 0 }

(Sorry to backpedal on this, I didn't realize it wasn't something we could test)

[MuVen, 2014/09/03 18:08:47]

Valid point !!! Changes Done.

+  scrollbar_layer->fake_scrollbar()->set_thumb_length(0);
+  scrollbar_layer->fake_scrollbar()->set_has_thumb(false);
+
+  UPDATE_AND_EXTRACT_LAYER_POINTERS();
+  EXPECT_EQ(gfx::Rect(10, 0, 0, 0).ToString(),
+            scrollbar_layer_impl->ComputeThumbQuadRect().ToString());
+}
+
 TEST(ScrollbarLayerTest, ThumbRect) {
   scoped_ptr<FakeLayerTreeHost> host = FakeLayerTreeHost::Create();
   scoped_refptr<Layer> root_clip_layer = Layer::Create();
   scoped_refptr<Layer> root_layer = Layer::Create();
   scoped_refptr<Layer> content_layer = Layer::Create();
   scoped_refptr<FakePaintedScrollbarLayer> scrollbar_layer =
       FakePaintedScrollbarLayer::Create(false, true, root_layer->id());
 
   root_layer->SetScrollClipLayerId(root_clip_layer->id());
   // Give the root-clip a size that will result in MaxScrollOffset = (80, 0).
@@ skipping 704 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