Implement HitTestAggregator

components/viz/service/hit_test/hit_test_aggregator.cc

+// Copyright 2017 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 "components/viz/service/hit_test/hit_test_aggregator.h"
+#include "components/viz/common/hit_test/display_hit_test_data.h"
+
+namespace viz {
+namespace hit_test {
+
+namespace {
+// TODO(gklassen): Review and select appropriate sizes ( based on

[rjkroege, 2017/06/27 00:00:07]

same nit about spaces and (

[gklassen, 2017/06/27 21:46:32]

Done.

+// telemetry / UMA? ).
+constexpr int kInitialSize = 1024;
+constexpr int kIncrementalSize = 1024;
+
+bool ValidateHitTestRegion(
+    const hit_test::mojom::HitTestRegionPtr& hit_test_region) {
+  if (hit_test_region->flags == hit_test::mojom::kHitTestChildSurface) {
+    if (!hit_test_region->surface_id.is_valid())
+      return false;
+  }
+  return true;
+}
+bool ValidateHitTestData(const hit_test::mojom::HitTestDataPtr& hit_test_data) {
+  for (auto& region : hit_test_data->regions) {
+    if (!ValidateHitTestRegion(region)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+}  // namespace
+
+HitTestAggregator::HitTestAggregator(
+    std::unique_ptr<DisplayHitTestDataFactory> display_hit_test_data_factory)
+    : active_region_count_(0),
+      display_hit_test_data_factory_(std::move(display_hit_test_data_factory)),
+      weak_ptr_factory_(this) {
+  AllocateDisplayHitTestData();
+}
+HitTestAggregator::~HitTestAggregator() {}
+
+void HitTestAggregator::SubmitHitTestData(
+    hit_test::mojom::HitTestDataPtr hit_test_data) {
+  DCHECK(ValidateHitTestData(hit_test_data));
+  // TODO(gklassen): Runtime validation that hit_test_data is valid.
+  // TODO(gklassen): Inform FrameSink that the hit_test_data is invalid.
+  // TODO(gklassen): FrameSink needs to inform the host of a difficult renderer.
+  pending_[hit_test_data->surface_id] = std::move(hit_test_data);
+}
+
+bool HitTestAggregator::OnSurfaceDamaged(const cc::SurfaceId& surface_id,
+                                         const cc::BeginFrameAck& ack) {
+  return false;
+}
+
+void HitTestAggregator::OnSurfaceDiscarded(const cc::SurfaceId& surface_id) {
+  pending_.erase(surface_id);
+  active_.erase(surface_id);
+}
+
+void HitTestAggregator::OnSurfaceWillDraw(const cc::SurfaceId& surface_id) {
+  auto pending_search = pending_.find(surface_id);
+  if (pending_search == pending_.end()) {
+    // Have already activated pending hit_test_data objects for this surface.
+    return;
+  }
+  hit_test::mojom::HitTestData* hit_test_data = pending_search->second.get();
+
+  // Update the region count.
+  auto active_search = active_.find(surface_id);
+  if (active_search != active_.end()) {
+    hit_test::mojom::HitTestData* old_hit_test_data =
+        active_search->second.get();
+    active_region_count_ -= old_hit_test_data->regions.size();
+  }
+  active_region_count_ += hit_test_data->regions.size();
+  DCHECK_GE(active_region_count_, 0);
+
+  active_[surface_id] = std::move(pending_[surface_id]);
+  pending_.erase(surface_id);
+}
+
+void HitTestAggregator::AllocateDisplayHitTestData() {
+  AllocateDisplayHitTestData(kInitialSize);
+  Swap();
+  AllocateDisplayHitTestData(kInitialSize);
+}
+
+void HitTestAggregator::AllocateDisplayHitTestData(int size) {
+  // TODO(gklassen): free old memory
+
+  size_t byte_count =
+      sizeof(DisplayHitTestData) + size * sizeof(DisplayHitTestRegion);
+  write_display_hit_test_data_ = (DisplayHitTestData*)malloc(byte_count);
+
+  write_display_hit_test_data_->size = size;
+  write_display_hit_test_data_->regions[0].child_count = kEndOfList;
+}
+
+void HitTestAggregator::PostTaskAggregate(cc::SurfaceId display_surface_id) {
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE,
+      base::BindOnce(&HitTestAggregator::Aggregate,
+                     weak_ptr_factory_.GetWeakPtr(), display_surface_id));
+}
+
+void HitTestAggregator::Aggregate(cc::SurfaceId display_surface_id) {
+  // Size check.
+  int size = write_display_hit_test_data_->size;
+  int max_size = active_region_count_ + active_.size() + 1;
+  if (max_size > size) {
+    while (size < max_size)

[rjkroege, 2017/06/27 00:00:07]

it is conceivable that a client could try to DoS us. There should be a check
here to detect a client that has attempted to create too many regions? 

[gklassen, 2017/06/27 21:46:32]

Done.

+      size += kIncrementalSize;
+    AllocateDisplayHitTestData(size);
+  }
+
+  AppendRoot(display_surface_id);
+}
+
+void HitTestAggregator::AppendRoot(cc::SurfaceId surface_id) {
+  auto search = active_.find(surface_id);
+  if (search == active_.end()) {

[rjkroege, 2017/06/27 00:00:07]

how this can happen?

[gklassen, 2017/06/27 21:46:32]

Done.

+    // Referenced surface not found ( it may be late ).
+    return;
+  }
+  hit_test::mojom::HitTestData* hit_test_data = search->second.get();
+
+  DisplayHitTestRegion* element = write_display_hit_test_data_->regions;
+
+  element->frame_sink_id = hit_test_data->surface_id.frame_sink_id();
+  element->flags = hit_test_data->flags;
+  element->rect = hit_test_data->bounds;
+  element->transform = hit_test_data->transform;
+
+  int index = 1;
+  for (auto& region : hit_test_data->regions) {
+    index = AppendRegion(region, index);
+  }
+  DCHECK_GE(index, 1);
+  element->child_count = index - 1;
+  write_display_hit_test_data_->regions[index].child_count = kEndOfList;
+}
+
+int HitTestAggregator::AppendRegion(
+    const hit_test::mojom::HitTestRegionPtr& region,
+    int index) {
+  DisplayHitTestRegion* element = &write_display_hit_test_data_->regions[index];
+
+  element->frame_sink_id = region->surface_id.frame_sink_id();
+  element->flags = region->flags;
+  element->rect = region->rect;
+  element->transform = region->transform;
+
+  int parent_index = index++;
+
+  if (region->flags == hit_test::mojom::kHitTestChildSurface) {

[rjkroege, 2017/06/27 00:00:07]

why is this possible? You are only activating surfaces that are in the Display
CompositorFrame right?

[gklassen, 2017/06/27 21:46:32]

Yes, we are only activating surfaces that are in the Display Compositor Frame.

It is possible that a surface references a child frame and that child's
Compositor Frame is late and not included in the Display Compositor Frame and
this check is to handle that case (assuming it's possible). 

+    auto search = active_.find(region->surface_id);
+    if (search == active_.end()) {
+      // Surface HitTestData not found - it may be late.
+      // Don't include this region so that it doesn't receive events.
+      // TODO(gklassen): create test case for this case.
+      return parent_index;
+    }
+
+    // Rather than add a node in the tree for this hit_test_data element
+    // we can simplify the tree by merging the flags and transform into
+    // the kHitTestChildSurface element.
+    hit_test::mojom::HitTestData* hit_test_data = search->second.get();
+    if (!hit_test_data->transform.IsIdentity()) {
+      // TODO(gklassen): Add test case to validate this.
+      element->transform.PreconcatTransform(hit_test_data->transform);
+    }
+    element->flags |= hit_test_data->flags;
+
+    for (auto& child_region : hit_test_data->regions) {
+      index = AppendRegion(child_region, index);
+    }
+  }
+  DCHECK_GE(index - parent_index - 1, 0);
+  element->child_count = index - parent_index - 1;
+  return index;
+}
+
+void HitTestAggregator::Swap() {
+  DisplayHitTestData* temp = read_display_hit_test_data_;
+  read_display_hit_test_data_ = write_display_hit_test_data_;
+  write_display_hit_test_data_ = temp;
+}
+
+DisplayHitTestRegion* HitTestAggregator::GetCurrentRegions() {
+  return read_display_hit_test_data_->regions;
+}
+
+}  // namespace hit_test
+}  // namespace viz