Implement service-side surface synchronization

cc/surfaces/surface_dependency_tracker.cc

Index: cc/surfaces/surface_dependency_tracker.cc
diff --git a/cc/surfaces/surface_dependency_tracker.cc b/cc/surfaces/surface_dependency_tracker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..934586bbb53757c654ba28c6d660b1359ff06ced
--- /dev/null
+++ b/cc/surfaces/surface_dependency_tracker.cc
@@ -0,0 +1,180 @@
+// Copyright 2016 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/surfaces/surface_dependency_tracker.h"
+
+#include "cc/surfaces/surface.h"
+#include "cc/surfaces/surface_info.h"
+#include "cc/surfaces/surface_manager.h"
+
+namespace cc {
+
+namespace {
+constexpr uint32_t kMaxBeginFrameCount = 4;
+}
+
+SurfaceDependencyTracker::SurfaceDependencyTracker(
+    SurfaceManager* surface_manager,
+    BeginFrameSource* begin_frame_source)
+    : surface_manager_(surface_manager),
+      begin_frame_source_(begin_frame_source) {
+  surface_manager_->AddObserver(this);
+  begin_frame_source_->AddObserver(this);
+}
+
+SurfaceDependencyTracker::~SurfaceDependencyTracker() {
+  surface_manager_->RemoveObserver(this);
+  begin_frame_source_->RemoveObserver(this);
+}
+
+void SurfaceDependencyTracker::RequestSurfaceResolution(Surface* surface) {
+  DCHECK(surface->HasPendingFrame());
+
+  const CompositorFrame& pending_frame = surface->GetPendingFrame();
+  bool needs_begin_frame =
+      pending_frame.metadata.can_activate_before_dependencies;
+
+  // Referenced surface IDs that aren't currently known to the surface manager
+  // or do not have an active CompsotiorFrame block this frame.
+  for (const SurfaceId& surface_id :
+       pending_frame.metadata.referenced_surfaces) {
+    Surface* surface_dependency = surface_manager_->GetSurfaceForId(surface_id);
+    if (!surface_dependency || !surface_dependency->HasActiveFrame())
+      blocked_surfaces_[surface_id].insert(surface);
+  }
+
+  if (!pending_surfaces_.count(surface)) {
+    surface->AddObserver(this);
+    pending_surfaces_.insert(surface);
+  }
+
+  if (needs_begin_frame && !frames_since_deadline_set_)
+    frames_since_deadline_set_ = 0;
+}
+
+void SurfaceDependencyTracker::OnBeginFrame(const BeginFrameArgs& args) {
+  // If no deadline is set then we have nothing to do.
+  if (!frames_since_deadline_set_)
+    return;
+
+  // TODO(fsamuel, kylechar): We have a single global deadline here. We should
+  // scope deadlines to surface subtrees. We cannot do that until
+  // SurfaceReferences have been fully implemented
+  // (see https://crbug.com/689719).
+  last_begin_frame_args_ = args;
+  // Nothing to do if we haven't hit a deadline yet.
+  if (++(*frames_since_deadline_set_) != kMaxBeginFrameCount)
+    return;
+
+  // Activate all surfaces that respect the deadline.
+  PendingSurfaceSet pending_surfaces(pending_surfaces_);
+  for (Surface* pending_surface : pending_surfaces)
+    pending_surface->ActivatePendingFrameForDeadline();
+
+  frames_since_deadline_set_.reset();
+}
+
+const BeginFrameArgs& SurfaceDependencyTracker::LastUsedBeginFrameArgs() const {
+  return last_begin_frame_args_;
+}
+
+void SurfaceDependencyTracker::OnBeginFrameSourcePausedChanged(bool paused) {}
+
+void SurfaceDependencyTracker::OnSurfaceDiscarded(Surface* surface) {
+  // If the surface being destroyed doesn't have a pending frame then we have
+  // nothing to do here.
+  if (!surface->HasPendingFrame())
+    return;
+
+  const CompositorFrame& pending_frame = surface->GetPendingFrame();
+
+  DCHECK(!pending_frame.metadata.referenced_surfaces.empty());
+
+  for (const SurfaceId& surface_id :
+       pending_frame.metadata.referenced_surfaces) {
+    auto it = blocked_surfaces_.find(surface_id);
+    if (it == blocked_surfaces_.end())
+      continue;
+
+    auto& pending_surface_set = it->second;
+    auto pending_surface_it = pending_surface_set.find(surface);
+    if (pending_surface_it != pending_surface_set.end()) {
+      pending_surface_set.erase(surface);
+      if (pending_surface_set.empty())
+        blocked_surfaces_.erase(surface_id);
+    }
+  }
+
+  if (blocked_surfaces_.empty())
+    frames_since_deadline_set_.reset();
+
+  pending_surfaces_.erase(surface);
+  surface->RemoveObserver(this);
+
+  // TODO(fsamuel): We should consider removing this surface as a dependency on
+  // other surfaces. This dependency will be removed when the deadline hits
+  // anyway but maybe we should try to actiate these frames early (see
+  // https://crbug.com/689725).
+}
+
+void SurfaceDependencyTracker::OnSurfaceActivated(Surface* surface) {
+  surface->RemoveObserver(this);
+  pending_surfaces_.erase(surface);
+  NotifySurfaceIdAvailable(surface->surface_id());
+}
+
+void SurfaceDependencyTracker::OnSurfaceDependenciesChanged(
+    Surface* surface,
+    const SurfaceDependencies& added_dependencies,
+    const SurfaceDependencies& removed_dependencies) {
+  // Update the |blocked_surfaces_| map with the changes in dependencies.
+  for (const SurfaceId& surface_id : added_dependencies)
+    blocked_surfaces_[surface_id].insert(surface);
+
+  for (const SurfaceId& surface_id : removed_dependencies) {
+    auto it = blocked_surfaces_.find(surface_id);
+    it->second.erase(surface);
+    if (it->second.empty())
+      blocked_surfaces_.erase(it);
+  }
+
+  // If there are no more dependencies to resolve then we don't need to have a
+  // deadline.
+  if (blocked_surfaces_.empty())
+    frames_since_deadline_set_.reset();
+}
+
+// SurfaceObserver implementation:
+void SurfaceDependencyTracker::OnSurfaceCreated(
+    const SurfaceInfo& surface_info) {
+  // This is called when a Surface has an activated frame for the first time.
+  // SurfaceDependencyTracker only observes Surfaces that contain pending
+  // frames. SurfaceDependencyTracker becomes aware of CompositorFrames that
+  // activate immediately go through here.
+  NotifySurfaceIdAvailable(surface_info.id());
+}
+
+void SurfaceDependencyTracker::OnSurfaceDamaged(const SurfaceId& surface_id,
+                                                bool* changed) {}
+
+void SurfaceDependencyTracker::NotifySurfaceIdAvailable(
+    const SurfaceId& surface_id) {
+  auto it = blocked_surfaces_.find(surface_id);
+  if (it == blocked_surfaces_.end())
+    return;
+
+  // Unblock surfaces that depend on this |surface_id|.
+  PendingSurfaceSet blocked_pending_surface_set(it->second);
+  blocked_surfaces_.erase(it);
+  // If there are no more blockers in the system, then we no longer need to
+  // have a deadline.
+  if (blocked_surfaces_.empty())
+    frames_since_deadline_set_.reset();
+
+  // Tell each surface about the availability of its blocker.
+  for (Surface* blocked_pending_surface : blocked_pending_surface_set)
+    blocked_pending_surface->NotifySurfaceIdAvailable(surface_id);
+}
+
+}  // namespace cc