src/ui/scenic/lib/flatland/link_system.cc

// Copyright 2019 The Fuchsia 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 "src/ui/scenic/lib/flatland/link_system.h"

#include "src/lib/fxl/logging.h"

using fuchsia::ui::scenic::internal::ContentLink;
using fuchsia::ui::scenic::internal::ContentLinkStatus;
using fuchsia::ui::scenic::internal::ContentLinkToken;
using fuchsia::ui::scenic::internal::GraphLink;
using fuchsia::ui::scenic::internal::GraphLinkStatus;
using fuchsia::ui::scenic::internal::GraphLinkToken;
using fuchsia::ui::scenic::internal::LayoutInfo;

namespace flatland {

LinkSystem::LinkSystem(TransformHandle::InstanceId instance_id)
    : instance_id_(instance_id), link_graph_(instance_id_) {}

LinkSystem::ChildLink LinkSystem::CreateChildLink(
    ContentLinkToken token, fuchsia::ui::scenic::internal::LinkProperties initial_properties,
    fidl::InterfaceRequest<ContentLink> content_link, TransformHandle graph_handle) {
  FXL_DCHECK(token.value.is_valid());

  auto impl = std::make_shared<GraphLinkImpl>();
  const TransformHandle link_handle = link_graph_.CreateTransform();

  ObjectLinker::ImportLink importer =
      linker_.CreateImport(std::move(content_link), std::move(token.value),
                           /* error_reporter */ nullptr);

  importer.Initialize(
      /* link_resolved = */
      [ref = shared_from_this(), impl = impl, graph_handle = graph_handle,
       link_handle = link_handle,
       initial_properties = std::move(initial_properties)](GraphLinkRequest request) {
        // Immediately send out the initial properties over the channel. This callback is fired from
        // one of the Flatland instance threads, but since we haven't stored the Link impl anywhere
        // yet, we still have exclusive access and can safely call functions without
        // synchronization.
        if (initial_properties.has_logical_size()) {
          LayoutInfo info;
          info.set_logical_size(initial_properties.logical_size());
          impl->UpdateLayoutInfo(std::move(info));
        }

        {
          // Mutate shared state while holding our mutex.
          std::scoped_lock lock(ref->map_mutex_);
          ref->graph_link_bindings_.AddBinding(impl, std::move(request.interface));
          ref->graph_link_map_[graph_handle] = impl;

          // The topology is constructed here, instead of in the link_resolved closure of the
          // ParentLink object, so that its destruction (which depends on the link_handle) can occur
          // on the same endpoint.
          ref->link_topologies_[link_handle] = request.child_handle;
        }
      },
      /* link_invalidated = */
      [ref = shared_from_this(), impl = impl, graph_handle = graph_handle,
       link_handle = link_handle](bool on_link_destruction) {
        {
          std::scoped_lock lock(ref->map_mutex_);
          ref->graph_link_map_.erase(graph_handle);
          ref->graph_link_bindings_.RemoveBinding(impl);

          ref->link_topologies_.erase(link_handle);
          ref->link_graph_.ReleaseTransform(link_handle);
        }
      });

  return ChildLink({
      .graph_handle = graph_handle,
      .link_handle = link_handle,
      .importer = std::move(importer),
  });
}

LinkSystem::ParentLink LinkSystem::CreateParentLink(GraphLinkToken token,
                                                    fidl::InterfaceRequest<GraphLink> graph_link,
                                                    TransformHandle link_origin) {
  FXL_DCHECK(token.value.is_valid());

  auto impl = std::make_shared<ContentLinkImpl>();

  ObjectLinker::ExportLink exporter =
      linker_.CreateExport({.interface = std::move(graph_link), .child_handle = link_origin},
                           std::move(token.value), /* error_reporter */ nullptr);

  exporter.Initialize(
      /* link_resolved = */
      [ref = shared_from_this(), impl = impl,
       link_origin = link_origin](fidl::InterfaceRequest<ContentLink> request) {
        std::scoped_lock lock(ref->map_mutex_);
        ref->content_link_bindings_.AddBinding(impl, std::move(request));
        ref->content_link_map_[link_origin] = impl;
      },
      /* link_invalidated = */
      [ref = shared_from_this(), impl = impl, link_origin = link_origin](bool on_link_destruction) {
        std::scoped_lock lock(ref->map_mutex_);
        ref->content_link_map_.erase(link_origin);
        ref->content_link_bindings_.RemoveBinding(impl);
      });

  return ParentLink({
      .link_origin = link_origin,
      .exporter = std::move(exporter),
  });
}

void LinkSystem::SetLinkProperties(TransformHandle handle,
                                   fuchsia::ui::scenic::internal::LinkProperties properties) {
  // Link properties should never be set on LinkSystem-created handles.
  FXL_DCHECK(handle.GetInstanceId() != instance_id_);

  std::scoped_lock lock(map_mutex_);
  link_properties_map_[handle] = std::move(properties);
}

void LinkSystem::ClearLinkProperties(TransformHandle handle) {
  // Link properties should never be set on LinkSystem-created handles.
  FXL_DCHECK(handle.GetInstanceId() != instance_id_);

  std::scoped_lock lock(map_mutex_);
  link_properties_map_.erase(handle);
}

void LinkSystem::UpdateLinks(const TransformGraph::TopologyVector& global_topology,
                             const std::unordered_set<TransformHandle>& live_handles) {
  std::scoped_lock lock(map_mutex_);

  for (auto& graph_link_kv : graph_link_map_) {
    graph_link_kv.second->UpdateLinkStatus(live_handles.count(graph_link_kv.first)
                                               ? GraphLinkStatus::CONNECTED_TO_DISPLAY
                                               : GraphLinkStatus::DISCONNECTED_FROM_DISPLAY);
  }

  for (const auto& entry : global_topology) {
    auto content_iter = content_link_map_.find(entry.handle);
    if (content_iter != content_link_map_.end()) {
      // Confirm that the ContentLink handle has at least one child (i.e., the link_origin of the
      // child Flatland instance). If not, then the child has not yet called Present().
      if (entry.child_count > 0) {
        content_iter->second->UpdateLinkStatus(ContentLinkStatus::CONTENT_HAS_PRESENTED);
      }
    }

    // For a particular Link, the LinkProperties and GraphLinkImpl both live on the ChildLink's
    // |link_handle|. They can show up in either order (LinkProperties before GraphLinkImpl if the
    // parent Flatland calls Present() first, other way around if the link resolves first), so one
    // being present without another is not a bug.
    auto properties_kv = link_properties_map_.find(entry.handle);
    if (properties_kv != link_properties_map_.end()) {
      auto graph_iter = graph_link_map_.find(entry.handle);
      if (graph_iter != graph_link_map_.end()) {
        if (properties_kv->second.has_logical_size()) {
          LayoutInfo info;
          info.set_logical_size(properties_kv->second.logical_size());
          graph_iter->second->UpdateLayoutInfo(std::move(info));
        }
      }
    }
  }
}

LinkSystem::LinkTopologyMap LinkSystem::GetResolvedTopologyLinks() {
  LinkTopologyMap copy;

  // Acquire the lock and copy.
  {
    std::scoped_lock lock(map_mutex_);
    copy = link_topologies_;
  }
  return copy;
}

TransformHandle::InstanceId LinkSystem::GetInstanceId() const { return instance_id_; }

}  // namespace flatland