// Copyright 2011 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/scheduler/scheduler.h"

#include <algorithm>
#include "base/auto_reset.h"
#include "base/debug/trace_event.h"
#include "base/logging.h"
#include "cc/debug/devtools_instrumentation.h"
#include "cc/debug/traced_value.h"
#include "ui/gfx/frame_time.h"

namespace cc {

Scheduler::Scheduler(SchedulerClient* client,
                     const SchedulerSettings& scheduler_settings,
                     int layer_tree_host_id)
    : settings_(scheduler_settings),
      client_(client),
      layer_tree_host_id_(layer_tree_host_id),
      last_set_needs_begin_impl_frame_(false),
      state_machine_(scheduler_settings),
      inside_process_scheduled_actions_(false),
      inside_action_(SchedulerStateMachine::ACTION_NONE),
      weak_factory_(this) {
  DCHECK(client_);
  DCHECK(!state_machine_.BeginImplFrameNeeded());
}

Scheduler::~Scheduler() {}

void Scheduler::SetCanStart() {
  state_machine_.SetCanStart();
  ProcessScheduledActions();
}

void Scheduler::SetVisible(bool visible) {
  state_machine_.SetVisible(visible);
  ProcessScheduledActions();
}

void Scheduler::SetCanDraw(bool can_draw) {
  state_machine_.SetCanDraw(can_draw);
  ProcessScheduledActions();
}

void Scheduler::NotifyReadyToActivate() {
  state_machine_.NotifyReadyToActivate();
  ProcessScheduledActions();
}

void Scheduler::ActivatePendingTree() {
  client_->ScheduledActionActivatePendingTree();
}

void Scheduler::SetNeedsCommit() {
  state_machine_.SetNeedsCommit();
  ProcessScheduledActions();
}

void Scheduler::SetNeedsForcedCommitForReadback() {
  state_machine_.SetNeedsCommit();
  state_machine_.SetNeedsForcedCommitForReadback();
  ProcessScheduledActions();
}

void Scheduler::SetNeedsRedraw() {
  state_machine_.SetNeedsRedraw();
  ProcessScheduledActions();
}

void Scheduler::SetNeedsManageTiles() {
  DCHECK(!IsInsideAction(SchedulerStateMachine::ACTION_MANAGE_TILES));
  state_machine_.SetNeedsManageTiles();
  ProcessScheduledActions();
}

void Scheduler::SetSwapUsedIncompleteTile(bool used_incomplete_tile) {
  state_machine_.SetSwapUsedIncompleteTile(used_incomplete_tile);
  ProcessScheduledActions();
}

void Scheduler::SetSmoothnessTakesPriority(bool smoothness_takes_priority) {
  state_machine_.SetSmoothnessTakesPriority(smoothness_takes_priority);
  ProcessScheduledActions();
}

void Scheduler::SetMainThreadNeedsLayerTextures() {
  state_machine_.SetMainThreadNeedsLayerTextures();
  ProcessScheduledActions();
}

void Scheduler::FinishCommit() {
  TRACE_EVENT0("cc", "Scheduler::FinishCommit");
  state_machine_.FinishCommit();
  ProcessScheduledActions();
}

void Scheduler::BeginMainFrameAborted(bool did_handle) {
  TRACE_EVENT0("cc", "Scheduler::BeginMainFrameAborted");
  state_machine_.BeginMainFrameAborted(did_handle);
  ProcessScheduledActions();
}

void Scheduler::DidManageTiles() {
  state_machine_.DidManageTiles();
}

void Scheduler::DidLoseOutputSurface() {
  TRACE_EVENT0("cc", "Scheduler::DidLoseOutputSurface");
  last_set_needs_begin_impl_frame_ = false;
  begin_impl_frame_deadline_closure_.Cancel();
  state_machine_.DidLoseOutputSurface();
  ProcessScheduledActions();
}

void Scheduler::DidCreateAndInitializeOutputSurface() {
  TRACE_EVENT0("cc", "Scheduler::DidCreateAndInitializeOutputSurface");
  DCHECK(!last_set_needs_begin_impl_frame_);
  DCHECK(begin_impl_frame_deadline_closure_.IsCancelled());
  state_machine_.DidCreateAndInitializeOutputSurface();
  ProcessScheduledActions();
}

base::TimeTicks Scheduler::AnticipatedDrawTime() {
  TRACE_EVENT0("cc", "Scheduler::AnticipatedDrawTime");

  if (!last_set_needs_begin_impl_frame_ ||
      last_begin_impl_frame_args_.interval <= base::TimeDelta())
    return base::TimeTicks();

  base::TimeTicks now = gfx::FrameTime::Now();
  base::TimeTicks timebase = std::max(last_begin_impl_frame_args_.frame_time,
                                      last_begin_impl_frame_args_.deadline);
  int64 intervals =
      1 + ((now - timebase) / last_begin_impl_frame_args_.interval);
  return timebase + (last_begin_impl_frame_args_.interval * intervals);
}

base::TimeTicks Scheduler::LastBeginImplFrameTime() {
  return last_begin_impl_frame_args_.frame_time;
}

void Scheduler::SetupNextBeginImplFrameIfNeeded() {
  bool needs_begin_impl_frame =
      state_machine_.BeginImplFrameNeeded();

  bool at_end_of_deadline =
      state_machine_.begin_impl_frame_state() ==
          SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE;

  bool should_call_set_needs_begin_impl_frame =
      // Always request the BeginImplFrame immediately if it wasn't needed
      // before.
      (needs_begin_impl_frame && !last_set_needs_begin_impl_frame_) ||
      // We always need to explicitly request our next BeginImplFrame.
      at_end_of_deadline;

  if (should_call_set_needs_begin_impl_frame) {
    client_->SetNeedsBeginImplFrame(needs_begin_impl_frame);
    last_set_needs_begin_impl_frame_ = needs_begin_impl_frame;
  }

  // Setup PollForAnticipatedDrawTriggers if we need to monitor state but
  // aren't expecting any more BeginImplFrames. This should only be needed by
  // the synchronous compositor when BeginImplFrameNeeded is false.
  if (state_machine_.ShouldPollForAnticipatedDrawTriggers()) {
    DCHECK(!state_machine_.SupportsProactiveBeginImplFrame());
    DCHECK(!needs_begin_impl_frame);
    if (poll_for_draw_triggers_closure_.IsCancelled()) {
      poll_for_draw_triggers_closure_.Reset(
          base::Bind(&Scheduler::PollForAnticipatedDrawTriggers,
                     weak_factory_.GetWeakPtr()));
      base::MessageLoop::current()->PostDelayedTask(
          FROM_HERE,
          poll_for_draw_triggers_closure_.callback(),
          last_begin_impl_frame_args_.interval);
    }
  } else {
    poll_for_draw_triggers_closure_.Cancel();

    // At this point we'd prefer to advance through the commit flow by
    // drawing a frame, however it's possible that the frame rate controller
    // will not give us a BeginImplFrame until the commit completes.  See
    // crbug.com/317430 for an example of a swap ack being held on commit. Thus
    // we set this repeating timer to poll on ProcessScheduledActions until we
    // successfully reach BeginImplFrame. Since we'd rather get a BeginImplFrame
    // by the normally mechanism, we set the interval to twice the interval from
    // the previous frame.
    if (state_machine_.IsCommitStateWaiting()) {
      advance_commit_state_timer_.Start(
          FROM_HERE,
          last_begin_impl_frame_args_.interval * 2,
          base::Bind(&Scheduler::ProcessScheduledActions,
                     base::Unretained(this)));
    }
  }
}

void Scheduler::BeginImplFrame(const BeginFrameArgs& args) {
  TRACE_EVENT0("cc", "Scheduler::BeginImplFrame");
  DCHECK(state_machine_.begin_impl_frame_state() ==
         SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
  DCHECK(state_machine_.HasInitializedOutputSurface());
  last_begin_impl_frame_args_ = args;
  last_begin_impl_frame_args_.deadline -= client_->DrawDurationEstimate();
  advance_commit_state_timer_.Stop();
  state_machine_.OnBeginImplFrame(last_begin_impl_frame_args_);

  if (settings_.switch_to_low_latency_if_possible) {
    state_machine_.SetSkipBeginMainFrameToReduceLatency(
        state_machine_.MainThreadIsInHighLatencyMode() &&
            CanCommitAndActivateBeforeDeadline());
  }

  ProcessScheduledActions();

  if (!state_machine_.HasInitializedOutputSurface())
    return;

  state_machine_.OnBeginImplFrameDeadlinePending();
  devtools_instrumentation::didBeginFrame(layer_tree_host_id_);
  if (settings_.using_synchronous_renderer_compositor) {
    // The synchronous renderer compositor has to make its GL calls
    // within this call to BeginImplFrame.
    // TODO(brianderson): Have the OutputSurface initiate the deadline tasks
    // so the sychronous renderer compositor can take advantage of splitting
    // up the BeginImplFrame and deadline as well.
    OnBeginImplFrameDeadline();
  } else if (!settings_.deadline_scheduling_enabled) {
    // We emulate the old non-deadline scheduler here by posting the
    // deadline task without any delay.
    PostBeginImplFrameDeadline(base::TimeTicks());
  } else if (state_machine_.ShouldTriggerBeginImplFrameDeadlineEarly()) {
    // We are ready to draw a new active tree immediately.
    PostBeginImplFrameDeadline(base::TimeTicks());
  } else if (state_machine_.needs_redraw()) {
    // We have an animation or fast input path on the impl thread that wants
    // to draw, so don't wait too long for a new active tree.
    PostBeginImplFrameDeadline(last_begin_impl_frame_args_.deadline);
  } else {
    // The impl thread doesn't have anything it wants to draw and we are just
    // waiting for a new active tree, so post the deadline for the next
    // expected BeginImplFrame start. This allows us to draw immediately when
    // there is a new active tree, instead of waiting for the next
    // BeginImplFrame.
    // TODO(brianderson): Handle long deadlines (that are past the next frame's
    // frame time) properly instead of using this hack.
    PostBeginImplFrameDeadline(last_begin_impl_frame_args_.frame_time +
                               last_begin_impl_frame_args_.interval);
  }
}

void Scheduler::PostBeginImplFrameDeadline(base::TimeTicks deadline) {
  begin_impl_frame_deadline_closure_.Cancel();
  begin_impl_frame_deadline_closure_.Reset(
      base::Bind(&Scheduler::OnBeginImplFrameDeadline,
                 weak_factory_.GetWeakPtr()));
  client_->PostBeginImplFrameDeadline(
      begin_impl_frame_deadline_closure_.callback(), deadline);
}

void Scheduler::OnBeginImplFrameDeadline() {
  TRACE_EVENT0("cc", "Scheduler::OnBeginImplFrameDeadline");
  DCHECK(state_machine_.HasInitializedOutputSurface());
  begin_impl_frame_deadline_closure_.Cancel();
  state_machine_.OnBeginImplFrameDeadline();
  ProcessScheduledActions();

  if (state_machine_.HasInitializedOutputSurface()) {
    // We only transition out of BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE when all
    // actions that occur back-to-back in response to entering
    // BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE have completed. This is important
    // because sending the BeginMainFrame will not occur if we transition to
    // BEGIN_IMPL_FRAME_STATE_IDLE too early.
    state_machine_.OnBeginImplFrameIdle();
  }

  client_->DidBeginImplFrameDeadline();
}

void Scheduler::PollForAnticipatedDrawTriggers() {
  TRACE_EVENT0("cc", "Scheduler::PollForAnticipatedDrawTriggers");
  poll_for_draw_triggers_closure_.Cancel();
  state_machine_.DidEnterPollForAnticipatedDrawTriggers();
  ProcessScheduledActions();
  state_machine_.DidLeavePollForAnticipatedDrawTriggers();
}

void Scheduler::DrawAndSwapIfPossible() {
  DrawSwapReadbackResult result =
      client_->ScheduledActionDrawAndSwapIfPossible();
  state_machine_.DidDrawIfPossibleCompleted(result.did_draw);
}

void Scheduler::DrawAndSwapForced() {
  client_->ScheduledActionDrawAndSwapForced();
}

void Scheduler::DrawAndReadback() {
  DrawSwapReadbackResult result = client_->ScheduledActionDrawAndReadback();
  DCHECK(!result.did_swap);
}

void Scheduler::ProcessScheduledActions() {
  // We do not allow ProcessScheduledActions to be recursive.
  // The top-level call will iteratively execute the next action for us anyway.
  if (inside_process_scheduled_actions_)
    return;

  base::AutoReset<bool> mark_inside(&inside_process_scheduled_actions_, true);

  SchedulerStateMachine::Action action;
  do {
    state_machine_.CheckInvariants();
    action = state_machine_.NextAction();
    TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler"),
                 "SchedulerStateMachine",
                 "state",
                 TracedValue::FromValue(state_machine_.AsValue().release()));
    state_machine_.UpdateState(action);
    base::AutoReset<SchedulerStateMachine::Action>
        mark_inside_action(&inside_action_, action);
    switch (action) {
      case SchedulerStateMachine::ACTION_NONE:
        break;
      case SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME:
        client_->ScheduledActionSendBeginMainFrame();
        break;
      case SchedulerStateMachine::ACTION_COMMIT:
        client_->ScheduledActionCommit();
        break;
      case SchedulerStateMachine::ACTION_UPDATE_VISIBLE_TILES:
        client_->ScheduledActionUpdateVisibleTiles();
        break;
      case SchedulerStateMachine::ACTION_ACTIVATE_PENDING_TREE:
        ActivatePendingTree();
        break;
      case SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE:
        DrawAndSwapIfPossible();
        break;
      case SchedulerStateMachine::ACTION_DRAW_AND_SWAP_FORCED:
        DrawAndSwapForced();
        break;
      case SchedulerStateMachine::ACTION_DRAW_AND_SWAP_ABORT:
        // No action is actually performed, but this allows the state machine to
        // advance out of its waiting to draw state without actually drawing.
        break;
      case SchedulerStateMachine::ACTION_DRAW_AND_READBACK:
        DrawAndReadback();
        break;
      case SchedulerStateMachine::ACTION_BEGIN_OUTPUT_SURFACE_CREATION:
        client_->ScheduledActionBeginOutputSurfaceCreation();
        break;
      case SchedulerStateMachine::ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD:
        client_->ScheduledActionAcquireLayerTexturesForMainThread();
        break;
      case SchedulerStateMachine::ACTION_MANAGE_TILES:
        client_->ScheduledActionManageTiles();
        break;
    }
  } while (action != SchedulerStateMachine::ACTION_NONE);

  SetupNextBeginImplFrameIfNeeded();
  client_->DidAnticipatedDrawTimeChange(AnticipatedDrawTime());

  if (state_machine_.ShouldTriggerBeginImplFrameDeadlineEarly())
    PostBeginImplFrameDeadline(base::TimeTicks());
}

bool Scheduler::WillDrawIfNeeded() const {
  return !state_machine_.PendingDrawsShouldBeAborted();
}

bool Scheduler::CanCommitAndActivateBeforeDeadline() const {
  // Check if the main thread computation and commit can be finished before the
  // impl thread's deadline.
  base::TimeTicks estimated_draw_time =
      last_begin_impl_frame_args_.frame_time +
      client_->BeginMainFrameToCommitDurationEstimate() +
      client_->CommitToActivateDurationEstimate();

  return estimated_draw_time < last_begin_impl_frame_args_.deadline;
}

}  // namespace cc