Pixels class prototype and test (not to be committed).

runtime/lib/pixels.dart

+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// TODO(regis): Move abstract class pixels to sdk/lib/core/pixels.dart:
+abstract class pixels extends num {
+  static const pixels NAN = 0px / 0px;
+  static const pixels INFINITY = 1px / 0px;
+  static const pixels NEGATIVE_INFINITY = -INFINITY;
+  // TODO(regis): Expand as needed with API documentation.
+}
+
+class _Pixels implements pixels {
+  static const int _SCALING_BITS = 6;
+  static const int _SCALING_FACTOR = 1 << _SCALING_BITS;
+  static const int _HALF_VALUE = _SCALING_FACTOR >> 1;
+  static const int _NAN_VALUE = (1 << 30) - 1;  // Same as kSmiMax32. Positive.
+  static const int _PLUS_INF_VALUE = _NAN_VALUE - 1;  // Same as kSmiMax32 - 1.
+  static const int _MINUS_INF_VALUE = -_PLUS_INF_VALUE;  // Same as kSmiMin32 + 2.
+
+  // TODO(regis): Detect _NAN_VALUE, _PLUS_INF_VALUE and _MINUS_INF_VALUE as
+  // operands to all operations and treat as non finite values, rather than min and max.
+
+  final int _value;
+  static const pixels _PLUS_ONE = const _Pixels(1 << _SCALING_BITS);
+  static const pixels _MINUS_ONE = const _Pixels(-1 << _SCALING_BITS);
+  static const pixels _PLUS_INF = const _Pixels(_PLUS_INF_VALUE);
+  static const pixels _MINUS_INF = const _Pixels(_MINUS_INF_VALUE);
+  static const pixels _NAN = const _Pixels(_NAN_VALUE);
+
+  // Argument is already a scaled value in valid range.
+  const _Pixels(int this._value);
+
+  // Argument is already a scaled value, but not necessarily in valid range.
+  _Pixels._clamp(int this._value) {
+    if (_value > _PLUS_INF_VALUE) _value = _PLUS_INF_VALUE;
+    else if (_value < _MINUS_INF_VALUE) _value = _MINUS_INF_VALUE;
+  }
+
+  factory _Pixels.fromInteger(int value) => new _Pixels._clamp(value << _SCALING_BITS);
+
+  factory _Pixels.fromDouble(double value) => value.toPixels();
+
+  _Pixels.fromPixelsLiteral(String value) {
+    final decimalPoint = ".".codeUnits.first;
+    final digit0 = "0".codeUnits.first;
+    final digit9 = "9".codeUnits.first;
+    var numerator = 0;
+    var denominator = 1;
+    bool seenDecimalPoint = false;
+    for (var i = 0; i < value.length; i++) {
+      var c = value.codeUnitAt(i);
+      if (!seenDecimalPoint && c == decimalPoint) {
+        seenDecimalPoint = true;
+      } else if (digit0 <= c && c <= digit9) {
+        numerator = numerator*10 + (c - digit0);
+        if (seenDecimalPoint) denominator *= 10;
+      } else {
+        break;  // TODO(regis): Error handling. Expect px or PX here.
+      }
+    }
+    _value = (numerator << _SCALING_BITS) ~/ denominator;
+    if (_value > _PLUS_INF_VALUE) _value = _PLUS_INF_VALUE;
+  }
+
+  Type get runtimeType => pixels;
+
+  int get _identityHashCode {
+    return _value;
+  }
+
+  num operator +(num other) {
+    return other._toDoubleOrPixels()._addFromPixels(this);
+  }
+  pixels _addFromPixels(pixels other) {
+    return other._add(this);
+  }
+  pixels _add(pixels other) {
+    return new _Pixels._clamp(_value + other._value);
+  }
+
+  num operator -(num other) {
+    return other._toDoubleOrPixels()._subFromPixels(this);
+  }
+  pixels _subFromPixels(pixels other) {
+    return other._sub(this);
+  }
+  pixels _sub(pixels other) {
+    return new _Pixels._clamp(_value - other._value);
+  }
+
+  num operator *(num other) {
+    return other._toDoubleOrPixels()._mulFromPixels(this);
+  }
+  pixels _mulFromPixels(pixels other) {
+    return other._mul(this);
+  }
+  pixels _mul(pixels other) {
+    // Use rounding.
+    return new _Pixels._clamp((_value*other._value + _HALF_VALUE) >> _SCALING_BITS);
+  }
+
+  num operator /(num other) {
+    return other._toDoubleOrPixels()._divFromPixels(this);
+  }
+  pixels _divFromPixels(pixels other) {
+    return other._div(this);
+  }
+  pixels _div(pixels other) {
+    if (other._value == 0) {
+      if (_value > 0) {
+        return _PLUS_INF;
+      } else if (_value == 0) {
+        return _NAN;
+      } else {
+        return _MINUS_INF;
+      }
+    }
+    return new _Pixels._clamp((_value << _SCALING_BITS) ~/ other._value);
+  }
+
+  num operator %(num other) {
+    return other._toDoubleOrPixels()._moduloFromPixels(this);
+  }
+  pixels _moduloFromPixels(pixels other) {
+    return other._modulo(this);
+  }
+  pixels _modulo(pixels other) {
+    var q = _div(other);  // TODO(regis): Check NAN.
+    if (other._value < 0) {
+      q = q.ceil();
+    } else {
+      q = q.floor();
+    }
+    return _sub(q.toPixels()._mul(other));
+  }
+
+  int operator ~/(num other) {
+    return other._toDoubleOrPixels()._truncDivFromPixels(this);
+  }
+  int _truncDivFromPixels(pixels other) {
+    return other._truncDiv(this);
+  }
+  int _truncDiv(pixels other) {
+    if (other._value == 0) throw const IntegerDivisionByZeroException();
+    return _value ~/ other._value;
+  }
+
+  num remainder(num other) {
+    return other._toDoubleOrPixels()._remainderFromPixels(this);
+  }
+  pixels _remainderFromPixels(pixels other) {
+    return other._remainder(this);
+  }
+  pixels _remainder(pixels other) {
+    if (other._value == 0) throw const IntegerDivisionByZeroException();
+    return new _Pixels._clamp(_value - other._value*(_value ~/ other._value));
+  }
+
+  pixels operator -() {
+    if (isNaN) return this;
+    return new _Pixels(-_value);
+  }
+
+  bool operator ==(other) {
+    if (!(other is num)) return false;
+    return other._equalToPixels(this);
+  }
+  bool _equalToPixels(pixels other) {
+    return other._equal(this);
+  }
+  bool _equal(pixels other) {
+    return _value == other._value;
+  }
+
+  bool _equalToInteger(int other) {
+    return _value == (other << _SCALING_BITS);
+  }
+
+  bool operator <(num other) {
+    return other > this;
+  }
+  bool operator >(num other) {
+    return other._greaterThanFromPixels(this);
+  }
+  bool _greaterThanFromPixels(pixels other) {
+    return other._value > _value;
+  }
+  bool operator >=(num other) {
+    return (this == other) || (this > other);
+  }
+  bool operator <=(num other) {
+    return (this == other) || (this < other);
+  }
+
+  pixels _addFromInteger(int other) {
+    return new _Pixels._clamp((other << _SCALING_BITS) + _value);
+  }
+
+  pixels _subFromInteger(int other) {
+    return new _Pixels._clamp((other << _SCALING_BITS) - _value);
+  }
+
+  pixels _mulFromInteger(int other) {
+    return new _Pixels._clamp(other * _value);
+  }
+
+  pixels _divFromInteger(int other) {
+    if (_value == 0) {
+      if (other > 0) {
+        return _PLUS_INF;
+      } else if (other == 0) {
+        return _NAN;
+      } else {
+        return _MINUS_INF;
+      }
+    }
+    return new _Pixels._clamp((other << (2*_SCALING_BITS)) ~/ _value);
+  }
+
+  pixels _moduloFromInteger(int other) {
+    var q = _divFromInteger(other);
+    if (_value < 0) {
+      q = q.ceil();
+    } else {
+      q = q.floor();
+    }
+    return _mul(q.toPixels())._subFromInteger(other);
+  }
+
+  int _truncDivFromInteger(int other) {
+    if (_value == 0) throw const IntegerDivisionByZeroException();
+    return (other << _SCALING_BITS) ~/ _value;
+  }
+
+  pixels _remainderFromInteger(int other) {
+    if (_value == 0) throw const IntegerDivisionByZeroException();
+    return new _Pixels._clamp(
+        (other << _SCALING_BITS) - _value*((other << _SCALING_BITS) ~/ _value));
+  }
+
+  bool _greaterThanFromInteger(int other) {
+    return (other << _SCALING_BITS) > _value;
+  }
+
+  bool get isNegative {
+    return _value < 0;
+  }
+
+  bool get isInfinite {
+    return (_value == _PLUS_INF_VALUE) || (_value == _MINUS_INF_VALUE);
+  }
+  bool get isNaN => _value == _NAN_VALUE;
+  bool get isFinite {
+    return (_value != _PLUS_INF_VALUE) &&
+           (_value != _MINUS_INF_VALUE) &&
+           (_value != _NAN_VALUE);
+  }
+
+  pixels abs() {
+    return isNegative ? -this : this;
+  }
+
+  pixels get sign {
+    if (_value > 0) return _PLUS_ONE;
+    if (_value < 0) return _MINUS_ONE;
+    return this;
+  }
+
+  int round() {
+    if (!isFinite) throw new UnsupportedError("Must be finite");
+    return (_value + _HALF_VALUE) >> _SCALING_BITS;
+  }
+  int floor() {
+    if (!isFinite) throw new UnsupportedError("Must be finite");
+    return _value >> _SCALING_BITS;
+  }
+  int ceil() {
+    if (!isFinite) throw new UnsupportedError("Must be finite");
+    return (_value + _SCALING_FACTOR - 1) >> _SCALING_BITS;
+  }
+  int truncate() {
+    if (!isFinite) throw new UnsupportedError("Must be finite");
+    return (_value + ((_value < 0) ? (_SCALING_FACTOR - 1) : 0)) >> _SCALING_BITS;
+  }
+
+  double roundToDouble() => round().toDouble();
+  double floorToDouble() => floor().toDouble();
+  double ceilToDouble() => ceil().toDouble();
+  double truncateToDouble() => truncate().toDouble();
+
+  num clamp(num lowerLimit, num upperLimit) {
+    if (lowerLimit is! num) {
+      throw new ArgumentError.value(lowerLimit, "lowerLimit", "not a number");
+    }
+    if (upperLimit is! num) {
+      throw new ArgumentError.value(upperLimit, "upperLimit", "not a number");
+    }
+
+    if (lowerLimit.compareTo(upperLimit) > 0) {
+      throw new ArgumentError(lowerLimit);
+    }
+    if (lowerLimit.isNaN) return lowerLimit;
+    if (this.compareTo(lowerLimit) < 0) return lowerLimit;
+    if (this.compareTo(upperLimit) > 0) return upperLimit;
+    return this;
+  }
+
+  int toInt() => truncate();  // TODO(regis): Should we use round() instead?
+  double toDouble() {
+    if (_value == _PLUS_INF_VALUE) return double.INFINITY;
+    if (_value == _MINUS_INF_VALUE) return double.NEGATIVE_INFINITY;
+    if (_value == _NAN_VALUE) return double.NAN;
+    return _value / _SCALING_FACTOR;
+  }
+  pixels toPixels() { return this; }
+  pixels _toDoubleOrPixels() { return this; }
+  num _toBigintIfInteger() { return this; }
+
+  String toString() => "${toDouble()}px";
+
+  int compareTo(num other) {
+    const int EQUAL = 0, LESS = -1, GREATER = 1;
+    if (isNaN) {
+      return GREATER;  // TODO(regis): Correct?
+    }
+    if (other is double) {
+      double d = other;
+      if (d.isInfinite) {
+        if (isInfinite) {
+          if (((d == double.NEGATIVE_INFINITY) && (_value < 0)) ||
+              ((d == double.INFINITY) && (_value > 0))) {
+            return EQUAL;
+          }
+        }
+        return _value > 0 ? GREATER : LESS;
+      }
+      if (d.isNaN) {
+        return LESS;  // TODO(regis): unless this.isNaN? See above.
+      }
+      if ((d == 0.0) && (_value == 0)) {
+        return d.isNegative ? GREATER : EQUAL;
+      }
+      other = other.toPixels();
+    }
+    if (this < other) {
+      return LESS;
+    } else if (this > other) {
+      return GREATER;
+    } else {
+      return EQUAL;
+    }
+  }
+}
+