ash: Avoid unnecessary laser pointer updates.

ash/laser/laser_pointer_controller.cc

 // 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 "ash/laser/laser_pointer_controller.h"
 
 #include "ash/common/system/chromeos/palette/palette_utils.h"
 #include "ash/laser/laser_pointer_view.h"
 #include "ash/shell.h"
 #include "ui/display/screen.h"
 #include "ui/views/widget/widget.h"
 
 namespace ash {
 namespace {
 
 // A point gets removed from the collection if it is older than
 // |kPointLifeDurationMs|.
 const int kPointLifeDurationMs = 200;
 
 // When no move events are being received we add a new point every
 // |kAddStationaryPointsDelayMs| so that points older than
 // |kPointLifeDurationMs| can get removed.
-const int kAddStationaryPointsDelayMs = 5;
+// Note: Using a delay less than the screen refresh interval will not
+// provide a visual benefit but instead just waste time performing
+// unnecessary updates. 16ms is the refresh interval on most devices.
+// TODO(reveman): Use real VSYNC interval instead of a hard-coded delay.
+const int kAddStationaryPointsDelayMs = 16;
 
 }  // namespace
 
 LaserPointerController::LaserPointerController()
     : stationary_timer_(new base::Timer(
           FROM_HERE,
           base::TimeDelta::FromMilliseconds(kAddStationaryPointsDelayMs),
           base::Bind(&LaserPointerController::AddStationaryPoint,
                      base::Unretained(this)),
           true /* is_repeating */)) {
@@ skipping 87 matching lines @@
   // add points when |laser_pointer_view_| is null.
   stationary_timer_->Stop();
   if (laser_pointer_view_) {
     is_fading_away_ = false;
     laser_pointer_view_.reset();
   }
 }
 
 void LaserPointerController::RestartTimer() {
   stationary_timer_repeat_count_ = 0;
-  if (!stationary_timer_->IsRunning())
-    stationary_timer_->Reset();
+  stationary_timer_->Reset();
 }
 
 void LaserPointerController::AddStationaryPoint() {
   if (is_fading_away_)
     laser_pointer_view_->UpdateTime();
   else
     laser_pointer_view_->AddNewPoint(current_stylus_location_);
 
   // We can stop repeating the timer once the stylus has been stationary for
   // longer than the life of a point.
   if (stationary_timer_repeat_count_ * kAddStationaryPointsDelayMs >=
       kPointLifeDurationMs) {
     stationary_timer_->Stop();
     // Reset the view if the timer expires and the view was in process of fading
     // away.
     if (is_fading_away_)
       DestroyLaserPointerView();
   }
   stationary_timer_repeat_count_++;
 }
 }  // namespace ash