[WIP] Move media/capture to device/capture

media/capture/content/capture_resolution_chooser.h

-// Copyright 2015 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_CAPTURE_CONTENT_CAPTURE_RESOLUTION_CHOOSER_H_
-#define MEDIA_CAPTURE_CONTENT_CAPTURE_RESOLUTION_CHOOSER_H_
-
-#include <vector>
-
-#include "media/base/video_capture_types.h"
-#include "media/capture/capture_export.h"
-#include "ui/gfx/geometry/size.h"
-
-namespace media {
-
-// Encapsulates the logic that determines the capture frame resolution based on:
-//   1. The configured maximum frame resolution and resolution change policy.
-//   2. Changes to resolution of the source content.
-//   3. Changes to the (externally-computed) target data volume, provided in
-//      terms of the number of pixels in the frame.
-//
-// CaptureResolutionChooser always computes capture sizes less than the maximum
-// frame size, and adheres to the configured resolution change policy.  Within
-// those hard limits, the capture size is computed to be as close to the
-// targeted frame area as possible.
-//
-// In variable-resolution use cases, the capture sizes are "snapped" to a small
-// (i.e., usually less than a dozen) set of possibilities.  This is to prevent
-// the end-to-end system from having to deal with rapidly-changing video frame
-// resolutions that results from providing a fine-grained range of values.  The
-// possibile snapped frame sizes are computed relative to the resolution of the
-// source content: They are the same or smaller in size, and are of the same
-// aspect ratio.
-class CAPTURE_EXPORT CaptureResolutionChooser {
- public:
-  // media::ResolutionChangePolicy determines whether the variable frame
-  // resolutions being computed must adhere to a fixed aspect ratio or not, or
-  // that there must only be a single fixed resolution.
-  CaptureResolutionChooser(const gfx::Size& max_frame_size,
-                           ResolutionChangePolicy resolution_change_policy);
-  ~CaptureResolutionChooser();
-
-  // Returns the current capture frame resolution to use.
-  gfx::Size capture_size() const { return capture_size_; }
-
-  // Updates the capture size based on a change in the resolution of the source
-  // content.
-  void SetSourceSize(const gfx::Size& source_size);
-
-  // Updates the capture size to target the given frame area, in terms of
-  // gfx::Size::GetArea().  The initial target frame area is the maximum int
-  // (i.e., always target the source size).
-  void SetTargetFrameArea(int area);
-
-  // Search functions to, given a frame |area|, return the nearest snapped frame
-  // size, or N size steps up/down.  Snapped frame sizes are based on the
-  // current source size.
-  gfx::Size FindNearestFrameSize(int area) const;
-  gfx::Size FindLargerFrameSize(int area, int num_steps_up) const;
-  gfx::Size FindSmallerFrameSize(int area, int num_steps_down) const;
-
- private:
-  // Called after any update that requires |capture_size_| be re-computed.
-  void RecomputeCaptureSize();
-
-  // Recomputes the |snapped_sizes_| cache.
-  void UpdateSnappedFrameSizes(const gfx::Size& constrained_size);
-
-  // Hard constraints.
-  const gfx::Size max_frame_size_;
-  const gfx::Size min_frame_size_;  // Computed from the ctor arguments.
-
-  // Specifies the set of heuristics to use.
-  const ResolutionChangePolicy resolution_change_policy_;
-
-  // |capture_size_| will be computed such that its area is as close to this
-  // value as possible.
-  int target_area_;
-
-  // The current computed capture frame resolution.
-  gfx::Size capture_size_;
-
-  // Cache of the set of possible values |capture_size_| can have, in order from
-  // smallest to largest.  This is recomputed whenever UpdateSnappedFrameSizes()
-  // is called.
-  std::vector<gfx::Size> snapped_sizes_;
-};
-
-}  // namespace media
-
-#endif  // MEDIA_CAPTURE_CONTENT_CAPTURE_RESOLUTION_CHOOSER_H_