Add utility set classes to support getUserMedia constraint proccessing.

content/renderer/media/media_stream_constraints_util_sets.h

Index: content/renderer/media/media_stream_constraints_util_sets.h
diff --git a/content/renderer/media/media_stream_constraints_util_sets.h b/content/renderer/media/media_stream_constraints_util_sets.h
new file mode 100644
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+++ b/content/renderer/media/media_stream_constraints_util_sets.h
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+// Copyright 2017 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 CONTENT_RENDERER_MEDIA_MEDIA_STREAM_CONSTRAINTS_UTIL_SETS_H_
+#define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_CONSTRAINTS_UTIL_SETS_H_
+
+#include <algorithm>
+#include <limits>
+#include <utility>
+#include <vector>
+
+#include "base/gtest_prod_util.h"
+#include "base/logging.h"
+#include "content/common/content_export.h"
+#include "content/renderer/media/media_stream_constraints_util.h"
+
+namespace blink {
+struct WebMediaTrackConstraintSet;
+}
+
+namespace content {
+
+// This class template represents a set of candidates suitable for a numeric
+// range-based constraint.
+template <typename T>
+class NumericRangeSet {
+ public:
+  NumericRangeSet() : min_(0), max_(DefaultMax()) {}
+  NumericRangeSet(T min, T max) : min_(min), max_(max) {}
+  NumericRangeSet(const NumericRangeSet& other) = default;
+  NumericRangeSet& operator=(const NumericRangeSet& other) = default;
+  ~NumericRangeSet() = default;
+
+  T Min() const { return min_; }
+  T Max() const { return max_; }
+  bool IsEmpty() const { return max_ < min_; }
+
+  NumericRangeSet Intersection(const NumericRangeSet& other) const {
+    return NumericRangeSet(std::max(min_, other.min_),
+                           std::min(max_, other.max_));
+  }
+
+  // Creates a NumericRangeSet based on the minimum and maximum values of
+  // |constraint|.
+  template <typename ConstraintType>
+  static auto FromConstraint(ConstraintType constraint)
+      -> NumericRangeSet<decltype(constraint.min())> {
+    return NumericRangeSet<decltype(constraint.min())>(
+        ConstraintHasMin(constraint) ? ConstraintMin(constraint) : 0,
+        ConstraintHasMax(constraint) ? ConstraintMax(constraint)
+                                     : DefaultMax());
+  }
+
+ private:
+  static inline T DefaultMax() {
+    return std::numeric_limits<T>::has_infinity
+               ? std::numeric_limits<T>::infinity()
+               : std::numeric_limits<T>::max();
+  }
+  T min_;
+  T max_;
+};
+
+// This class defines a set of discrete elements suitable for resolving
+// constraints with a countable number of choices not suitable to be constrained
+// by range. Examples are strings, booleans and certain constraints of type
+// long. A DiscreteSet can be empty, have their elements explicitly stated, or
+// be the universal set. The universal set is a set that contains all possible
+// elements. The specific definition of what elements are in the universal set
+// is application defined (e.g., it could be all possible boolean values, all
+// possible strings of length N, or anything that suits a particular
+// application).
+template <typename T>
+class DiscreteSet {
+ public:
+  // Creates a set containing the elements in |elements|.
+  // It is the responsibility of the caller to ensure that |elements| is not
+  // equivalent to the universal set and that |elements| has no repeated
+  // values. Takes ownership of |elements|.
+  explicit DiscreteSet(std::vector<T> elements)
+      : is_universal_(false), elements_(std::move(elements)) {}
+  // Creates an empty set;
+  static DiscreteSet EmptySet() { return DiscreteSet(std::vector<T>()); }
+  static DiscreteSet UniversalSet() { return DiscreteSet(); }
+
+  DiscreteSet(const DiscreteSet& other) = default;
+  DiscreteSet& operator=(const DiscreteSet& other) = default;
+  DiscreteSet(DiscreteSet&& other) = default;
+  DiscreteSet& operator=(DiscreteSet&& other) = default;
+  ~DiscreteSet() = default;
+
+  bool Contains(const T& value) const {
+    return is_universal_ || std::find(elements_.begin(), elements_.end(),
+                                      value) != elements_.end();
+  }
+
+  bool IsEmpty() const { return !is_universal_ && elements_.empty(); }
+
+  bool HasExplicitElements() const { return !elements_.empty(); }
+
+  DiscreteSet Intersection(const DiscreteSet& other) const {
+    if (is_universal_)
+      return other;
+    if (other.is_universal_)
+      return *this;
+    if (IsEmpty() || other.IsEmpty())
+      return EmptySet();
+
+    // Both sets have explicit elements.
+    std::vector<T> intersection;
+    for (const auto& entry : elements_) {
+      auto it =
+          std::find(other.elements_.begin(), other.elements_.end(), entry);
+      if (it != other.elements_.end()) {
+        intersection.push_back(entry);
+      }
+    }
+    return DiscreteSet(std::move(intersection));
+  }
+
+  // Returns a copy of the first element in the set. This is useful as a simple
+  // tie-breaker rule. This applies only to constrained nonempty sets.
+  // Behavior is undefined if the set is empty or universal.
+  T FirstElement() const {
+    DCHECK(HasExplicitElements());
+    return elements_[0];
+  }
+
+  bool is_universal() const { return is_universal_; }
+
+ private:
+  // Creates a universal set.
+  DiscreteSet() : is_universal_(true) {}
+
+  bool is_universal_;
+  std::vector<T> elements_;
+};
+
+// This class represents a set of (height, width) screen resolution candidates
+// determined by width, height and aspect-ratio constraints.
+// This class supports widths and heights from 0 to kMaxDimension, both
+// inclusive and aspect ratios from 0.0 to positive infinity, both inclusive.
+class CONTENT_EXPORT ResolutionSet {
+ public:
+  static constexpr int kMaxDimension = std::numeric_limits<int>::max();
+
+  // Helper class that represents (height, width) points on a plane.
+  // TODO(guidou): Use a generic point/vector class that uses double once it
+  // becomes available (e.g., a gfx::Vector2dD).
+  class CONTENT_EXPORT Point {
+   public:
+    // Creates a (|height|, |width|) point. |height| and |width| must be finite.
+    Point(double height, double width);
+    Point(const Point& other);
+    Point& operator=(const Point& other);
+    ~Point();
+
+    // Accessors.
+    double height() const { return height_; }
+    double width() const { return width_; }
+    double AspectRatio() const { return width_ / height_; }
+
+    // Exact equality/inequality operators.
+    bool operator==(const Point& other) const;
+    bool operator!=(const Point& other) const;
+
+    // Returns true if the coordinates of this point and |other| are
+    // approximately equal.
+    bool IsApproximatelyEqualTo(const Point& other) const;
+
+    // Vector-style addition and subtraction operators.
+    Point operator+(const Point& other) const;
+    Point operator-(const Point& other) const;
+
+    // Returns the dot product between |p1| and |p2|.
+    static double Dot(const Point& p1, const Point& p2);
+
+    // Returns the square Euclidean distance between |p1| and |p2|.
+    static double SquareEuclideanDistance(const Point& p1, const Point& p2);
+
+    // Returns the point in the line segment determined by |s1| and |s2| that
+    // is closest to |p|.
+    static Point ClosestPointInSegment(const Point& p,
+                                       const Point& s1,
+                                       const Point& s2);
+
+   private:
+    double height_;
+    double width_;
+  };
+
+  // Creates a set with the maximum supported ranges for width, height and
+  // aspect ratio.
+  ResolutionSet();
+  ResolutionSet(int min_height,
+                int max_height,
+                int min_width,
+                int max_width,
+                double min_aspect_ratio,
+                double max_aspect_ratio);
+  ResolutionSet(const ResolutionSet& other);
+  ResolutionSet& operator=(const ResolutionSet& other);
+  ~ResolutionSet();
+
+  // Getters.
+  int min_height() const { return min_height_; }
+  int max_height() const { return max_height_; }
+  int min_width() const { return min_width_; }
+  int max_width() const { return max_width_; }
+  double min_aspect_ratio() const { return min_aspect_ratio_; }
+  double max_aspect_ratio() const { return max_aspect_ratio_; }
+
+  // Returns true if this set is empty.
+  bool IsEmpty() const;
+
+  // These functions return true if a particular variable causes the set to be
+  // empty.
+  bool IsHeightEmpty() const;
+  bool IsWidthEmpty() const;
+  bool IsAspectRatioEmpty() const;
+
+  // These functions return true if the given point is included in this set.
+  bool ContainsPoint(const Point& point) const;
+  bool ContainsPoint(int height, int width) const;
+
+  // Returns a new set with the intersection of |*this| and |other|.
+  ResolutionSet Intersection(const ResolutionSet& other) const;
+
+  // Returns a point in this (nonempty) set closest to the ideal values for the
+  // height, width and aspectRatio constraints in |constraint_set|.
+  // Note that this function ignores all the other data in |constraint_set|.
+  // Only the ideal height, width and aspect ratio are used, and from now on
+  // referred to as |ideal_height|, |ideal_width| and |ideal_aspect_ratio|
+  // respectively.
+  //
+  // * If all three ideal values are given, |ideal_aspect_ratio| is ignored and
+  //   the point closest to (|ideal_height|, |ideal_width|) is returned.
+  // * If two ideal values are given, they are used to determine a single ideal
+  //   point, which can be one of:
+  //    - (|ideal_height|, |ideal_width|),
+  //    - (|ideal_height|, |ideal_height|*|ideal_aspect_ratio|), or
+  //    - (|ideal_width| / |ideal_aspect_ratio|, |ideal_width|).
+  //   The point in the set closest to the ideal point is returned.
+  // * If a single ideal value is given, a point in the set closest to the line
+  //   defined by the ideal value is returned. If there is more than one point
+  //   closest to the ideal line, the following tie-breaker rules are used:
+  //  - If |ideal_height| is provided, the point closest to
+  //      (|ideal_height|, |ideal_height| * kDefaultAspectRatio).
+  //  - If |ideal_width| is provided, the point closest to
+  //      (|ideal_width| / kDefaultAspectRatio, |ideal_width|).
+  //  - If |ideal_aspect_ratio| is provided, the point with largest area among
+  //    the points closest to
+  //      (kDefaultHeight, kDefaultHeight * aspect_ratio) and
+  //      (kDefaultWidth / aspect_ratio, kDefaultWidth),
+  //    where aspect_ratio is |ideal_aspect_ratio| if the ideal line intersects
+  //    the set, and the closest aspect ratio to |ideal_aspect_ratio| among the
+  //    points in the set if no point in the set has an aspect ratio equal to
+  //    |ideal_aspect_ratio|.
+  // * If no ideal value is given, proceed as if only |ideal_aspect_ratio| was
+  //   provided with a value of kDefaultAspectRatio.
+  //
+  // This is intended to support the implementation of the spec algorithm for
+  // selection of track settings, as defined in
+  // https://w3c.github.io/mediacapture-main/#dfn-selectsettings.
+  //
+  // The main difference between this algorithm and the spec is that when ideal
+  // values are provided, the spec mandates finding a point that minimizes the
+  // sum of custom relative distances for each provided ideal value, while this
+  // algorithm minimizes either the Euclidean distance (sum of square distances)
+  // on a height-width plane for the cases where two or three ideal values are
+  // provided, or the absolute distance for the case with one ideal value.
+  // Also, in the case with three ideal values, this algorithm ignores the
+  // distance to the ideal aspect ratio.
+  // In most cases the difference in the final result should be negligible.
+  // The reason to follow this approach is that optimization in the worst case
+  // is reduced to projection of a point on line segment, which is a simple
+  // operation that provides exact results. Using the distance function of the
+  // spec, which is not continuous, would require complex optimization methods
+  // that do not necessarily guarantee finding the real optimal value.
+  //
+  // This function has undefined behavior if this set is empty.
+  Point SelectClosestPointToIdeal(
+      const blink::WebMediaTrackConstraintSet& constraint_set) const;
+
+  // Utilities that return ResolutionSets constrained on a specific variable.
+  static ResolutionSet FromHeight(int min, int max);
+  static ResolutionSet FromExactHeight(int value);
+  static ResolutionSet FromWidth(int min, int max);
+  static ResolutionSet FromExactWidth(int value);
+  static ResolutionSet FromAspectRatio(double min, double max);
+  static ResolutionSet FromExactAspectRatio(double value);
+
+  // Returns a ResolutionCandidateSet initialized with |constraint_set|'s
+  // width, height and aspectRatio constraints.
+  static ResolutionSet FromConstraintSet(
+      const blink::WebMediaTrackConstraintSet& constraint_set);
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(MediaStreamConstraintsUtilSetsTest,
+                           ResolutionVertices);
+  FRIEND_TEST_ALL_PREFIXES(MediaStreamConstraintsUtilSetsTest,
+                           ResolutionPointSetClosestPoint);
+  FRIEND_TEST_ALL_PREFIXES(MediaStreamConstraintsUtilSetsTest,
+                           ResolutionLineSetClosestPoint);
+  FRIEND_TEST_ALL_PREFIXES(MediaStreamConstraintsUtilSetsTest,
+                           ResolutionGeneralSetClosestPoint);
+  FRIEND_TEST_ALL_PREFIXES(MediaStreamConstraintsUtilSetsTest,
+                           ResolutionIdealOutsideSinglePoint);
+
+  // Implements SelectClosestPointToIdeal() for the case when only the ideal
+  // aspect ratio is provided.
+  Point SelectClosestPointToIdealAspectRatio(double ideal_aspect_ratio) const;
+
+  // Returns the closest point in this set to |point|. If |point| is included in
+  // this set, Point is returned. If this set is empty, behavior is undefined.
+  Point ClosestPointTo(const Point& point) const;
+
+  // Returns the vertices of the set that have the property accessed
+  // by |accessor| closest to |value|. The returned vector always has one or two
+  // elements. Behavior is undefined if the set is empty.
+  std::vector<Point> GetClosestVertices(double (Point::*accessor)() const,
+                                        double value) const;
+
+  // Returns a list of the vertices defined by the constraints on a height-width
+  // Cartesian plane.
+  // If the list is empty, the set is empty.
+  // If the list contains a single point, the set contains a single point.
+  // If the list contains two points, the set is composed of points on a line
+  // segment.
+  // If the list contains three to six points, they are the vertices of a
+  // convex polygon containing all valid points in the set. Each pair of
+  // consecutive vertices (modulo the size of the list) corresponds to a side of
+  // the polygon, with the vertices given in counterclockwise order.
+  // The list cannot contain more than six points.
+  std::vector<Point> ComputeVertices() const;
+
+  // Adds |point| to |vertices| if |point| is included in this candidate set.
+  void TryAddVertex(std::vector<ResolutionSet::Point>* vertices,
+                    const ResolutionSet::Point& point) const;
+
+  int min_height_;
+  int max_height_;
+  int min_width_;
+  int max_width_;
+  double min_aspect_ratio_;
+  double max_aspect_ratio_;
+};
+
+// Scalar multiplication for Points.
+ResolutionSet::Point CONTENT_EXPORT operator*(double d,
+                                              const ResolutionSet::Point& p);
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_CONSTRAINTS_UTIL_SETS_H_