Fix media timeline so that thumb never exceeds buffered data

media/base/clock.h

 // Copyright (c) 2012 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.
 
 #ifndef MEDIA_BASE_CLOCK_H_
 #define MEDIA_BASE_CLOCK_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time.h"
@@ skipping 30 matching lines @@
   base::TimeDelta Play();
 
   // Stops the clock and returns the current media time, which will remain
   // constant until Play() is called.
   base::TimeDelta Pause();
 
   // Sets a new playback rate.  The rate at which the media time will increase
   // will now change.
   void SetPlaybackRate(float playback_rate);
 
-  // Forcefully sets the media time to the given time.  This should only be used
-  // where a discontinuity in the media is found (i.e., seeking).
-  void SetTime(const base::TimeDelta& time);
+  // Forcefully sets the media time to |current_time|. The second parameter is
+  // the |max_time| that the clock should progress after a call to Play(). This
+  // value is often the time of the end of the last frame buffered and decoded.
+  void SetTime(base::TimeDelta current_time, base::TimeDelta max_time);

[acolwell GONE FROM CHROMIUM, 2012/01/13 22:51:21]

Comment should mention that the values are clamped by duration_

[vrk (LEFT CHROMIUM), 2012/01/21 00:54:14]

Done.

+
+  void set_max_time(base::TimeDelta max_time) {
+    max_time_ = max_time;

[acolwell GONE FROM CHROMIUM, 2012/01/13 22:51:21]

Implementation should be in .cc & should be clamped to 0 <= max_time <=
duration_

[vrk (LEFT CHROMIUM), 2012/01/21 00:54:14]

Done.

+  }
 
   // Returns the current elapsed media time.
   base::TimeDelta Elapsed() const;
 
+  void set_media_duration(base::TimeDelta duration) { duration_ = duration; }

[acolwell GONE FROM CHROMIUM, 2012/01/13 22:51:21]

How about dropping media?
Impl in .cc & DCHECK(duration >= base::TimeDelta())
We should probably also add a DCHECK() to make sure duration_ doesn't get
smaller if it has already been set. If that was allowed it could cause the clock
to go backwards!

[vrk (LEFT CHROMIUM), 2012/01/21 00:54:14]

Done.

+  base::TimeDelta media_duration() { return duration_; }
+
  private:
   // Returns the current media time treating the given time as the latest
   // value as returned by |time_provider_|.
   base::TimeDelta ElapsedViaProvidedTime(const base::Time& time) const;
 
   base::Time GetTimeFromProvider() const;
 
   // Function returning current time in base::Time units.
   TimeProvider* time_provider_;
 
   // Whether the clock is running.
   bool playing_;
 
   // The system clock time when this clock last starting playing or had its
   // time set via SetTime().
   base::Time reference_;
 
   // Current accumulated amount of media time.  The remaining portion must be
   // calculated by comparing the system time to the reference time.
   base::TimeDelta media_time_;
 
   // Current playback rate.
   float playback_rate_;
 
+  // The maximum time that can be returned by calls to GetCurrentTime.
+  base::TimeDelta max_time_;
+
+  // Duration of the media.
+  base::TimeDelta duration_;
+
   DISALLOW_COPY_AND_ASSIGN(Clock);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_CLOCK_H_