Arrange compositor scrolling into scroll customization format

cc/layers/layer_impl.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 "cc/layers/layer_impl.h"
 
 #include "base/json/json_reader.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
 #include "cc/animation/animation_registrar.h"
 #include "cc/animation/scrollbar_animation_controller.h"
 #include "cc/base/math_util.h"
 #include "cc/base/simple_enclosed_region.h"
 #include "cc/debug/debug_colors.h"
 #include "cc/debug/layer_tree_debug_state.h"
 #include "cc/debug/micro_benchmark_impl.h"
 #include "cc/debug/traced_value.h"
+#include "cc/input/scroll_state.h"
 #include "cc/layers/layer_utils.h"
 #include "cc/layers/painted_scrollbar_layer_impl.h"
 #include "cc/output/copy_output_request.h"
 #include "cc/quads/debug_border_draw_quad.h"
 #include "cc/quads/render_pass.h"
 #include "cc/trees/layer_tree_host_common.h"
 #include "cc/trees/layer_tree_impl.h"
 #include "cc/trees/layer_tree_settings.h"
 #include "cc/trees/proxy.h"
 #include "ui/gfx/geometry/box_f.h"
@@ skipping 160 matching lines @@
   SetNeedsPushProperties();
 }
 
 void LayerImpl::SetScrollChildren(std::set<LayerImpl*>* children) {
   if (scroll_children_.get() == children)
     return;
   scroll_children_.reset(children);
   SetNeedsPushProperties();
 }
 
+void LayerImpl::DistributeScroll(ScrollState* scroll_state) {
+  DCHECK(scroll_state);
+  if (scroll_state->FullyConsumed())
+    return;
+
+  scroll_state->DistributeToScrollChainDescendant();
+
+  // If the scroll doesn't propagate, and we're currently scrolling
+  // a layer other than this one, prevent the scroll from
+  // propagating to this layer.
+  if (!scroll_state->should_propagate() &&
+      scroll_state->delta_consumed_for_scroll_sequence() &&

[Ian Vollick, 2015/07/30 19:02:25]

Hmm, what if we shouldn't propagate, and the true scrolling layer (that isn't
us) decides not to consume any scroll delta. Won't this cause us to ApplyScroll
incorrectly here? Or by not consuming any scrolling is it relinquishing the
right to be the scrolling layer?

[tdresser, 2015/07/30 20:34:20]

delta_consumed_for_scroll_sequence persists for the duration of the scroll.

The only case where we shouldn't propagate is within a touchscreen fling. In
this case, we want to scroll the very first scroller that scrolls, not
necessarily the innermost scroller.

So essentially yes, but not consuming any scroll it's relinquishing the right to
be the scrolling layer.

+      scroll_state->current_native_scrolling_layer() != this) {
+    return;
+  }
+
+  ApplyScroll(scroll_state);
+}
+
+void LayerImpl::ApplyScroll(ScrollState* scroll_state) {
+  DCHECK(scroll_state);
+  layer_tree_impl()->ApplyScroll(this, scroll_state);
+}
+
 void LayerImpl::SetNumDescendantsThatDrawContent(int num_descendants) {
   if (num_descendants_that_draw_content_ == num_descendants)
     return;
   num_descendants_that_draw_content_ = num_descendants;
   SetNeedsPushProperties();
 }
 
 void LayerImpl::SetClipParent(LayerImpl* ancestor) {
   if (clip_parent_ == ancestor)
     return;
@@ skipping 1639 matching lines @@
   }
 
   // TODO(enne): the transform needs to come from property trees instead of
   // draw properties.
   gfx::Vector2dF transform_scales = MathUtil::ComputeTransform2dScaleComponents(
       draw_properties().target_space_transform, default_scale);
   return std::max(transform_scales.x(), transform_scales.y());
 }
 
 }  // namespace cc