Implement service-side surface synchronization

cc/surfaces/surface.cc

 // Copyright 2014 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.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
 
 #include "cc/base/container_util.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/output/copy_output_request.h"
+#include "cc/surfaces/pending_frame_observer.h"
 #include "cc/surfaces/surface_factory.h"
 #include "cc/surfaces/surface_id_allocator.h"
 #include "cc/surfaces/surface_manager.h"
 
 namespace cc {
 
 // The frame index starts at 2 so that empty frames will be treated as
 // completely damaged the first time they're drawn from.
 static const int kFrameIndexStart = 2;
 
 Surface::Surface(const SurfaceId& id, base::WeakPtr<SurfaceFactory> factory)
     : surface_id_(id),
       previous_frame_surface_id_(id),
       factory_(factory),
       frame_index_(kFrameIndexStart),
       destroyed_(false) {}
 
 Surface::~Surface() {
   ClearCopyRequests();
-  if (current_frame_ && factory_) {
-    UnrefFrameResources(*current_frame_);
+  if (factory_) {
+    if (pending_frame_)
+      UnrefFrameResources(*pending_frame_);
+    if (active_frame_)
+      UnrefFrameResources(*active_frame_);
   }
   if (!draw_callback_.is_null())
     draw_callback_.Run();
+
+  for (auto& observer : observers_)
+    observer.OnSurfaceDiscarded(this);
+  observers_.Clear();
 }
 
 void Surface::SetPreviousFrameSurface(Surface* surface) {
   DCHECK(surface);
   frame_index_ = surface->frame_index() + 1;
   previous_frame_surface_id_ = surface->surface_id();
 }
 
 void Surface::QueueFrame(CompositorFrame frame, const DrawCallback& callback) {

[vmpstr, 2017/02/07 22:46:19]

Can you extract the code between lines 60 and 96 to a helper function, something
like:

UpdateBlockedSurfaces(previous_pending_frame, frame);

? I think that might read better

[Fady Samuel, 2017/02/08 00:52:49]

Done.

-  DCHECK(factory_);
-  ClearCopyRequests();
+  base::Optional<CompositorFrame> previous_pending_frame =
+      std::move(pending_frame_);
+  pending_frame_.reset();
 
-  TakeLatencyInfo(&frame.metadata.latency_info);
+  std::unordered_set<SurfaceId, SurfaceIdHash> new_blocked_on_surfaces;
 
-  base::Optional<CompositorFrame> previous_frame = std::move(current_frame_);
-  current_frame_ = std::move(frame);
-
-  if (current_frame_) {
-    factory_->ReceiveFromChild(current_frame_->resource_list);
+  for (const SurfaceId& surface_id : frame.metadata.referenced_surfaces) {
+    Surface* surface = factory_->manager()->GetSurfaceForId(surface_id);
+    // If a referenced surface does not have a corresponding active frame in the
+    // display compositor, then it blocks this frame.
+    if (!surface || !surface->HasActiveFrame())
+      new_blocked_on_surfaces.insert(surface_id);
   }
 
-  // Empty frames shouldn't be drawn and shouldn't contribute damage, so don't
-  // increment frame index for them.
-  if (current_frame_ && !current_frame_->render_pass_list.empty()) {
-    ++frame_index_;
+  // If this Surface has a previous pending frame, then we must determine the
+  // changes in dependencies so that we can update the
+  // DisplayCompositorLockManager map.
+  if (previous_pending_frame.has_value()) {
+    SurfaceDependencies added_dependencies;

[vmpstr, 2017/02/07 22:46:19]

move this to right before the second for loop please, so it's clear which loop
populates what

[Fady Samuel, 2017/02/08 00:52:49]

Done.

+    SurfaceDependencies removed_dependencies;
+
+    for (const SurfaceId& surface_id : blocked_on_surfaces_) {

[vmpstr, 2017/02/07 22:46:19]

If you use flat_sets which are ordered, then I think you could use
std::set_difference here, but tbh I think this is fine.

[Fady Samuel, 2017/02/08 00:52:49]

I'll leave it as is for now.

+      if (!new_blocked_on_surfaces.count(surface_id))
+        removed_dependencies.insert(surface_id);
+    }
+
+    for (const SurfaceId& surface_id : new_blocked_on_surfaces) {
+      if (!blocked_on_surfaces_.count(surface_id))
+        added_dependencies.insert(surface_id);
+    }
+
+    // If there is a change in the dependency set, then inform observers.
+    if (!added_dependencies.empty() || !removed_dependencies.empty()) {
+      for (auto& observer : observers_) {
+        observer.OnSurfaceChanged(this, added_dependencies,
+                                  removed_dependencies);
+      }
+    }
   }
 
-  previous_frame_surface_id_ = surface_id();
+  blocked_on_surfaces_ = std::move(new_blocked_on_surfaces);
 
-  if (previous_frame)
-    UnrefFrameResources(*previous_frame);
+  if (!blocked_on_surfaces_.empty()) {
+    pending_frame_ = std::move(frame);
+    if (pending_frame_) {
+      factory_->ReceiveFromChild(pending_frame_->resource_list);
+      // Ask the surface manager to inform |this| when its dependencies are
+      // resolved.
+      factory_->manager()->RequestSurfaceResolution(this);
+    }
+  } else {
+    // If there are no blockers, then immediately activate the frame.
+    ActivateFrame(std::move(frame));
+  }
+
+  // Returns resources for the previous pending frame.
+  if (previous_pending_frame)
+    UnrefFrameResources(*previous_pending_frame);
 
   if (!draw_callback_.is_null())
     draw_callback_.Run();
   draw_callback_ = callback;
-
-  referenced_surfaces_ = current_frame_->metadata.referenced_surfaces;
 }
 
 void Surface::EvictFrame() {
   QueueFrame(CompositorFrame(), DrawCallback());
-  current_frame_.reset();
+  active_frame_.reset();
 }
 
 void Surface::RequestCopyOfOutput(
     std::unique_ptr<CopyOutputRequest> copy_request) {
-  if (current_frame_ && !current_frame_->render_pass_list.empty()) {
+  if (active_frame_ && !active_frame_->render_pass_list.empty()) {

[vmpstr, 2017/02/07 22:46:19]

minor nit: while here, I think this would read better as

if (!active_frame_ || active_frame_->render_pass_list.empty()) {
  copy_request->SendEmptyResult();
  return;
}

...

[Fady Samuel, 2017/02/08 00:52:49]

Done.

     std::vector<std::unique_ptr<CopyOutputRequest>>& copy_requests =
-        current_frame_->render_pass_list.back()->copy_requests;
+        active_frame_->render_pass_list.back()->copy_requests;
 
     if (copy_request->has_source()) {
       const base::UnguessableToken& source = copy_request->source();
       // Remove existing CopyOutputRequests made on the Surface by the same
       // source.
       auto to_remove = std::remove_if(
           copy_requests.begin(), copy_requests.end(),
           [&source](const std::unique_ptr<CopyOutputRequest>& x) {
             return x->has_source() && x->source() == source;
           });
       copy_requests.erase(to_remove, copy_requests.end());
     }
     copy_requests.push_back(std::move(copy_request));
   } else {
     copy_request->SendEmptyResult();
   }
 }
 
+void Surface::ReportSurfaceIdAvailable(const SurfaceId& surface_id) {
+  auto it = blocked_on_surfaces_.find(surface_id);
+  // This surface may no longer have blockers if the deadline has passed.
+  if (it == blocked_on_surfaces_.end())
+    return;
+
+  blocked_on_surfaces_.erase(it);
+
+  if (!blocked_on_surfaces_.empty())
+    return;
+
+  // All blockers have been cleared. The surface can be activated now.
+  ActivatePendingFrame();

[vmpstr, 2017/02/07 22:46:19]

Are we guaranteed to have a pending frame at this point?

[Fady Samuel, 2017/02/08 00:52:49]

We got this far, which means we had a blocker (and thus a pending frame), that
blocker was cleared, and now we can activate the pending frame so I think we are
guaranteed to have a pending frame at this point. I have a DCHECK in
ActivatePendingFrame.

+}
+
+void Surface::AddObserver(PendingFrameObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void Surface::RemoveObserver(PendingFrameObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void Surface::ActivatePendingFrameForDeadline() {
+  if (!pending_frame_ || !pending_frame_->metadata.respect_deadline)
+    return;
+
+  // If a frame is being activated because of a deadline, then clear its set
+  // of blockers.
+  blocked_on_surfaces_.clear();
+  ActivatePendingFrame();
+}
+
+void Surface::ActivatePendingFrame() {
+  ActivateFrame(std::move(pending_frame_.value()));
+  pending_frame_.reset();
+  // ActiveFrame resources are now double ref-ed. Unref.
+  UnrefFrameResources(*active_frame_);
+}
+
+void Surface::ActivateFrame(CompositorFrame frame) {

[vmpstr, 2017/02/07 22:46:19]

Can you add a comment at the top of the function to just outline what it takes
to activate a frame

[Fady Samuel, 2017/02/08 00:52:49]

Done.

+  DCHECK(factory_);
+  ClearCopyRequests();
+
+  TakeLatencyInfo(&frame.metadata.latency_info);
+
+  base::Optional<CompositorFrame> previous_frame = std::move(active_frame_);
+  active_frame_ = std::move(frame);
+
+  if (active_frame_)

[vmpstr, 2017/02/07 22:46:19]

In what situations can we not have an active_frame_ here?

Also, you can combine this if with the next one

if (active_frame) {
  ...
  if (!active_frame->render_pass_list_empty())
    ...
}

[Fady Samuel, 2017/02/08 00:52:49]

Heh, We just set the active_frame_ so we should have an active_frame_. I think
this is cruft that carried over from old code.

+    factory_->ReceiveFromChild(active_frame_->resource_list);
+
+  // Empty frames shouldn't be drawn and shouldn't contribute damage, so don't
+  // increment frame index for them.
+  if (active_frame_ && !active_frame_->render_pass_list.empty())
+    ++frame_index_;
+
+  previous_frame_surface_id_ = surface_id();
+
+  if (previous_frame)
+    UnrefFrameResources(*previous_frame);
+
+  referenced_surfaces_ = active_frame_->metadata.referenced_surfaces;
+
+  for (auto& observer : observers_)
+    observer.OnSurfaceActivated(this);
+}
+
 void Surface::TakeCopyOutputRequests(
     std::multimap<int, std::unique_ptr<CopyOutputRequest>>* copy_requests) {
   DCHECK(copy_requests->empty());
-  if (current_frame_) {
-    for (const auto& render_pass : current_frame_->render_pass_list) {
+  if (active_frame_) {

[vmpstr, 2017/02/07 22:46:19]

nit:

if (!active_frame_)
  return;

...

[Fady Samuel, 2017/02/08 00:52:49]

Done.

+    for (const auto& render_pass : active_frame_->render_pass_list) {
       for (auto& request : render_pass->copy_requests) {
         copy_requests->insert(
             std::make_pair(render_pass->id, std::move(request)));
       }
       render_pass->copy_requests.clear();
     }
   }
 }
 
-const CompositorFrame& Surface::GetEligibleFrame() const {
-  DCHECK(current_frame_);
-  return current_frame_.value();
+const CompositorFrame& Surface::GetActiveFrame() const {
+  DCHECK(active_frame_);
+  return active_frame_.value();
+}
+
+const CompositorFrame& Surface::GetPendingFrame() {
+  DCHECK(pending_frame_);
+  return pending_frame_.value();
 }
 
 void Surface::TakeLatencyInfo(std::vector<ui::LatencyInfo>* latency_info) {
-  if (!current_frame_)
+  if (!active_frame_)
     return;
   if (latency_info->empty()) {
-    current_frame_->metadata.latency_info.swap(*latency_info);
+    active_frame_->metadata.latency_info.swap(*latency_info);
     return;
   }
-  std::copy(current_frame_->metadata.latency_info.begin(),
-            current_frame_->metadata.latency_info.end(),
+  std::copy(active_frame_->metadata.latency_info.begin(),
+            active_frame_->metadata.latency_info.end(),
             std::back_inserter(*latency_info));
-  current_frame_->metadata.latency_info.clear();
+  active_frame_->metadata.latency_info.clear();
 }
 
 void Surface::RunDrawCallbacks() {
   if (!draw_callback_.is_null()) {
     DrawCallback callback = draw_callback_;
     draw_callback_ = DrawCallback();
     callback.Run();
   }
 }
 
@@ skipping 17 matching lines @@
 void Surface::UnrefFrameResources(const CompositorFrame& frame) {
   ReturnedResourceArray resources;
   TransferableResource::ReturnResources(frame.resource_list, &resources);
   // No point in returning same sync token to sender.
   for (auto& resource : resources)
     resource.sync_token.Clear();
   factory_->UnrefResources(resources);
 }
 
 void Surface::ClearCopyRequests() {
-  if (current_frame_) {
-    for (const auto& render_pass : current_frame_->render_pass_list) {
+  if (active_frame_) {
+    for (const auto& render_pass : active_frame_->render_pass_list) {
       for (const auto& copy_request : render_pass->copy_requests)
         copy_request->SendEmptyResult();
     }
   }
 }
 
 }  // namespace cc