yoga/java/com/facebook/yoga/YogaConstants.java

/*
 *  Copyright (c) Facebook, Inc. and its affiliates.
 *
 *  This source code is licensed under the MIT license found in the LICENSE
 *  file in the root directory of this source tree.
 *
 */
package com.facebook.yoga;

public class YogaConstants {

  /**
   * Large positive number signifies that the property(float) is undefined. Earlier we used to have
   * YGundefined as NAN, but the downside of this is that we can't use -ffast-math compiler flag as
   * it assumes all floating-point calculation involve and result into finite numbers. For more
   * information regarding -ffast-math compiler flag in clang, have a look at
   * https://clang.llvm.org/docs/UsersManual.html#cmdoption-ffast-math
   */
  public static final float UNDEFINED = (float) (10E20);

  public static boolean isUndefined(float value) {
    // Value of a float in the case of it being not defined is 10.1E20. Earlier it used to be NAN,
    // the benefit of which
    // was that if NAN is involved in any mathematical expression the result was NAN. But since we
    // want to have `-ffast-math`
    // flag being used by compiler which assumes that the floating point values are not NAN and Inf,
    // we represent YGUndefined as 10.1E20.
    // But now if YGUndefined is involved in any mathematical operations this value(10.1E20) would
    // change.
    // So the following check makes sure that if the value is outside a range (-10E8, 10E8) then it
    // is undefined.
    return (Float.compare(value, (float) 10E8) >= 0 || Float.compare(value, (float) -10E8) <= 0);
  }

  public static boolean isUndefined(YogaValue value) {
    return value.unit == YogaUnit.UNDEFINED;
  }

  public static float getUndefined() {
    return UNDEFINED;
  }
}