/*
* Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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package javax.swing;
import java.awt.
Component;
/**
* An instance of the <code>Spring</code> class holds three properties that
* characterize its behavior: the <em>minimum</em>, <em>preferred</em>, and
* <em>maximum</em> values. Each of these properties may be involved in
* defining its fourth, <em>value</em>, property based on a series of rules.
* <p>
* An instance of the <code>Spring</code> class can be visualized as a
* mechanical spring that provides a corrective force as the spring is compressed
* or stretched away from its preferred value. This force is modelled
* as linear function of the distance from the preferred value, but with
* two different constants -- one for the compressional force and one for the
* tensional one. Those constants are specified by the minimum and maximum
* values of the spring such that a spring at its minimum value produces an
* equal and opposite force to that which is created when it is at its
* maximum value. The difference between the <em>preferred</em> and
* <em>minimum</em> values, therefore, represents the ease with which the
* spring can be compressed and the difference between its <em>maximum</em>
* and <em>preferred</em> values, indicates the ease with which the
* <code>Spring</code> can be extended.
* See the {@link #sum} method for details.
*
* <p>
* By defining simple arithmetic operations on <code>Spring</code>s,
* the behavior of a collection of <code>Spring</code>s
* can be reduced to that of an ordinary (non-compound) <code>Spring</code>. We define
* the "+", "-", <em>max</em>, and <em>min</em> operators on
* <code>Spring</code>s so that, in each case, the result is a <code>Spring</code>
* whose characteristics bear a useful mathematical relationship to its constituent
* springs.
*
* <p>
* A <code>Spring</code> can be treated as a pair of intervals
* with a single common point: the preferred value.
* The following rules define some of the
* arithmetic operators that can be applied to intervals
* (<code>[a, b]</code> refers to the interval
* from <code>a</code>
* to <code>b</code>,
* where <code>a <= b</code>).
*
* <pre>
* [a1, b1] + [a2, b2] = [a1 + a2, b1 + b2]
*
* -[a, b] = [-b, -a]
*
* max([a1, b1], [a2, b2]) = [max(a1, a2), max(b1, b2)]
* </pre>
* <p>
*
* If we denote <code>Spring</code>s as <code>[a, b, c]</code>,
* where <code>a <= b <= c</code>, we can define the same
* arithmetic operators on <code>Spring</code>s:
*
* <pre>
* [a1, b1, c1] + [a2, b2, c2] = [a1 + a2, b1 + b2, c1 + c2]
*
* -[a, b, c] = [-c, -b, -a]
*
* max([a1, b1, c1], [a2, b2, c2]) = [max(a1, a2), max(b1, b2), max(c1, c2)]
* </pre>
* <p>
* With both intervals and <code>Spring</code>s we can define "-" and <em>min</em>
* in terms of negation:
*
* <pre>
* X - Y = X + (-Y)
*
* min(X, Y) = -max(-X, -Y)
* </pre>
* <p>
* For the static methods in this class that embody the arithmetic
* operators, we do not actually perform the operation in question as
* that would snapshot the values of the properties of the method's arguments
* at the time the static method is called. Instead, the static methods
* create a new <code>Spring</code> instance containing references to
* the method's arguments so that the characteristics of the new spring track the
* potentially changing characteristics of the springs from which it
* was made. This is a little like the idea of a <em>lazy value</em>
* in a functional language.
* <p>
* If you are implementing a <code>SpringLayout</code> you
* can find further information and examples in
* <a
href="https://docs.oracle.com/javase/tutorial/uiswing/layout/spring.html">How to Use SpringLayout</a>,
* a section in <em>The Java Tutorial.</em>
* <p>
* <strong>Warning:</strong>
* Serialized objects of this class will not be compatible with
* future Swing releases. The current serialization support is
* appropriate for short term storage or RMI between applications running
* the same version of Swing. As of 1.4, support for long term storage
* of all JavaBeans™
* has been added to the <code>java.beans</code> package.
* Please see {@link java.beans.XMLEncoder}.
*
* @see SpringLayout
* @see SpringLayout.Constraints
*
* @author Philip Milne
* @since 1.4
*/
public abstract class
Spring {
/**
* An integer value signifying that a property value has not yet been calculated.
*/
public static final int
UNSET =
Integer.
MIN_VALUE;
/**
* Used by factory methods to create a <code>Spring</code>.
*
* @see #constant(int)
* @see #constant(int, int, int)
* @see #max
* @see #minus
* @see #sum
* @see SpringLayout.Constraints
*/
protected
Spring() {}
/**
* Returns the <em>minimum</em> value of this <code>Spring</code>.
*
* @return the <code>minimumValue</code> property of this <code>Spring</code>
*/
public abstract int
getMinimumValue();
/**
* Returns the <em>preferred</em> value of this <code>Spring</code>.
*
* @return the <code>preferredValue</code> of this <code>Spring</code>
*/
public abstract int
getPreferredValue();
/**
* Returns the <em>maximum</em> value of this <code>Spring</code>.
*
* @return the <code>maximumValue</code> property of this <code>Spring</code>
*/
public abstract int
getMaximumValue();
/**
* Returns the current <em>value</em> of this <code>Spring</code>.
*
* @return the <code>value</code> property of this <code>Spring</code>
*
* @see #setValue
*/
public abstract int
getValue();
/**
* Sets the current <em>value</em> of this <code>Spring</code> to <code>value</code>.
*
* @param value the new setting of the <code>value</code> property
*
* @see #getValue
*/
public abstract void
setValue(int
value);
private double
range(boolean
contract) {
return
contract ? (
getPreferredValue() -
getMinimumValue()) :
(
getMaximumValue() -
getPreferredValue());
}
/*pp*/ double
getStrain() {
double
delta = (
getValue() -
getPreferredValue());
return
delta/
range(
getValue() <
getPreferredValue());
}
/*pp*/ void
setStrain(double
strain) {
setValue(
getPreferredValue() + (int)(
strain *
range(
strain < 0)));
}
/*pp*/ boolean
isCyclic(
SpringLayout l) {
return false;
}
/*pp*/ static abstract class
AbstractSpring extends
Spring {
protected int
size =
UNSET;
public int
getValue() {
return
size !=
UNSET ?
size :
getPreferredValue();
}
public final void
setValue(int
size) {
if (this.
size ==
size) {
return;
}
if (
size ==
UNSET) {
clear();
} else {
setNonClearValue(
size);
}
}
protected void
clear() {
size =
UNSET;
}
protected void
setNonClearValue(int
size) {
this.
size =
size;
}
}
private static class
StaticSpring extends
AbstractSpring {
protected int
min;
protected int
pref;
protected int
max;
public
StaticSpring(int
pref) {
this(
pref,
pref,
pref);
}
public
StaticSpring(int
min, int
pref, int
max) {
this.
min =
min;
this.
pref =
pref;
this.
max =
max;
}
public
String toString() {
return "StaticSpring [" +
min + ", " +
pref + ", " +
max + "]";
}
public int
getMinimumValue() {
return
min;
}
public int
getPreferredValue() {
return
pref;
}
public int
getMaximumValue() {
return
max;
}
}
private static class
NegativeSpring extends
Spring {
private
Spring s;
public
NegativeSpring(
Spring s) {
this.
s =
s;
}
// Note the use of max value rather than minimum value here.
// See the opening preamble on arithmetic with springs.
public int
getMinimumValue() {
return -
s.
getMaximumValue();
}
public int
getPreferredValue() {
return -
s.
getPreferredValue();
}
public int
getMaximumValue() {
return -
s.
getMinimumValue();
}
public int
getValue() {
return -
s.
getValue();
}
public void
setValue(int
size) {
// No need to check for UNSET as
// Integer.MIN_VALUE == -Integer.MIN_VALUE.
s.
setValue(-
size);
}
/*pp*/ boolean
isCyclic(
SpringLayout l) {
return
s.
isCyclic(
l);
}
}
private static class
ScaleSpring extends
Spring {
private
Spring s;
private float
factor;
private
ScaleSpring(
Spring s, float
factor) {
this.
s =
s;
this.
factor =
factor;
}
public int
getMinimumValue() {
return
Math.
round((
factor < 0 ?
s.
getMaximumValue() :
s.
getMinimumValue()) *
factor);
}
public int
getPreferredValue() {
return
Math.
round(
s.
getPreferredValue() *
factor);
}
public int
getMaximumValue() {
return
Math.
round((
factor < 0 ?
s.
getMinimumValue() :
s.
getMaximumValue()) *
factor);
}
public int
getValue() {
return
Math.
round(
s.
getValue() *
factor);
}
public void
setValue(int
value) {
if (
value ==
UNSET) {
s.
setValue(
UNSET);
} else {
s.
setValue(
Math.
round(
value /
factor));
}
}
/*pp*/ boolean
isCyclic(
SpringLayout l) {
return
s.
isCyclic(
l);
}
}
/*pp*/ static class
WidthSpring extends
AbstractSpring {
/*pp*/
Component c;
public
WidthSpring(
Component c) {
this.
c =
c;
}
public int
getMinimumValue() {
return
c.
getMinimumSize().
width;
}
public int
getPreferredValue() {
return
c.
getPreferredSize().
width;
}
public int
getMaximumValue() {
// We will be doing arithmetic with the results of this call,
// so if a returned value is Integer.MAX_VALUE we will get
// arithmetic overflow. Truncate such values.
return
Math.
min(
Short.
MAX_VALUE,
c.
getMaximumSize().
width);
}
}
/*pp*/ static class
HeightSpring extends
AbstractSpring {
/*pp*/
Component c;
public
HeightSpring(
Component c) {
this.
c =
c;
}
public int
getMinimumValue() {
return
c.
getMinimumSize().
height;
}
public int
getPreferredValue() {
return
c.
getPreferredSize().
height;
}
public int
getMaximumValue() {
return
Math.
min(
Short.
MAX_VALUE,
c.
getMaximumSize().
height);
}
}
/*pp*/ static abstract class
SpringMap extends
Spring {
private
Spring s;
public
SpringMap(
Spring s) {
this.
s =
s;
}
protected abstract int
map(int
i);
protected abstract int
inv(int
i);
public int
getMinimumValue() {
return
map(
s.
getMinimumValue());
}
public int
getPreferredValue() {
return
map(
s.
getPreferredValue());
}
public int
getMaximumValue() {
return
Math.
min(
Short.
MAX_VALUE,
map(
s.
getMaximumValue()));
}
public int
getValue() {
return
map(
s.
getValue());
}
public void
setValue(int
value) {
if (
value ==
UNSET) {
s.
setValue(
UNSET);
} else {
s.
setValue(
inv(
value));
}
}
/*pp*/ boolean
isCyclic(
SpringLayout l) {
return
s.
isCyclic(
l);
}
}
// Use the instance variables of the StaticSpring superclass to
// cache values that have already been calculated.
/*pp*/ static abstract class
CompoundSpring extends
StaticSpring {
protected
Spring s1;
protected
Spring s2;
public
CompoundSpring(
Spring s1,
Spring s2) {
super(
UNSET);
this.
s1 =
s1;
this.
s2 =
s2;
}
public
String toString() {
return "CompoundSpring of " +
s1 + " and " +
s2;
}
protected void
clear() {
super.clear();
min =
pref =
max =
UNSET;
s1.
setValue(
UNSET);
s2.
setValue(
UNSET);
}
protected abstract int
op(int
x, int
y);
public int
getMinimumValue() {
if (
min ==
UNSET) {
min =
op(
s1.
getMinimumValue(),
s2.
getMinimumValue());
}
return
min;
}
public int
getPreferredValue() {
if (
pref ==
UNSET) {
pref =
op(
s1.
getPreferredValue(),
s2.
getPreferredValue());
}
return
pref;
}
public int
getMaximumValue() {
if (
max ==
UNSET) {
max =
op(
s1.
getMaximumValue(),
s2.
getMaximumValue());
}
return
max;
}
public int
getValue() {
if (
size ==
UNSET) {
size =
op(
s1.
getValue(),
s2.
getValue());
}
return
size;
}
/*pp*/ boolean
isCyclic(
SpringLayout l) {
return
l.
isCyclic(
s1) ||
l.
isCyclic(
s2);
}
};
private static class
SumSpring extends
CompoundSpring {
public
SumSpring(
Spring s1,
Spring s2) {
super(
s1,
s2);
}
protected int
op(int
x, int
y) {
return
x +
y;
}
protected void
setNonClearValue(int
size) {
super.setNonClearValue(
size);
s1.
setStrain(this.
getStrain());
s2.
setValue(
size -
s1.
getValue());
}
}
private static class
MaxSpring extends
CompoundSpring {
public
MaxSpring(
Spring s1,
Spring s2) {
super(
s1,
s2);
}
protected int
op(int
x, int
y) {
return
Math.
max(
x,
y);
}
protected void
setNonClearValue(int
size) {
super.setNonClearValue(
size);
s1.
setValue(
size);
s2.
setValue(
size);
}
}
/**
* Returns a strut -- a spring whose <em>minimum</em>, <em>preferred</em>, and
* <em>maximum</em> values each have the value <code>pref</code>.
*
* @param pref the <em>minimum</em>, <em>preferred</em>, and
* <em>maximum</em> values of the new spring
* @return a spring whose <em>minimum</em>, <em>preferred</em>, and
* <em>maximum</em> values each have the value <code>pref</code>
*
* @see Spring
*/
public static
Spring constant(int
pref) {
return
constant(
pref,
pref,
pref);
}
/**
* Returns a spring whose <em>minimum</em>, <em>preferred</em>, and
* <em>maximum</em> values have the values: <code>min</code>, <code>pref</code>,
* and <code>max</code> respectively.
*
* @param min the <em>minimum</em> value of the new spring
* @param pref the <em>preferred</em> value of the new spring
* @param max the <em>maximum</em> value of the new spring
* @return a spring whose <em>minimum</em>, <em>preferred</em>, and
* <em>maximum</em> values have the values: <code>min</code>, <code>pref</code>,
* and <code>max</code> respectively
*
* @see Spring
*/
public static
Spring constant(int
min, int
pref, int
max) {
return new
StaticSpring(
min,
pref,
max);
}
/**
* Returns <code>-s</code>: a spring running in the opposite direction to <code>s</code>.
*
* @return <code>-s</code>: a spring running in the opposite direction to <code>s</code>
*
* @see Spring
*/
public static
Spring minus(
Spring s) {
return new
NegativeSpring(
s);
}
/**
* Returns <code>s1+s2</code>: a spring representing <code>s1</code> and <code>s2</code>
* in series. In a sum, <code>s3</code>, of two springs, <code>s1</code> and <code>s2</code>,
* the <em>strains</em> of <code>s1</code>, <code>s2</code>, and <code>s3</code> are maintained
* at the same level (to within the precision implied by their integer <em>value</em>s).
* The strain of a spring in compression is:
* <pre>
* value - pref
* ------------
* pref - min
* </pre>
* and the strain of a spring in tension is:
* <pre>
* value - pref
* ------------
* max - pref
* </pre>
* When <code>setValue</code> is called on the sum spring, <code>s3</code>, the strain
* in <code>s3</code> is calculated using one of the formulas above. Once the strain of
* the sum is known, the <em>value</em>s of <code>s1</code> and <code>s2</code> are
* then set so that they are have a strain equal to that of the sum. The formulas are
* evaluated so as to take rounding errors into account and ensure that the sum of
* the <em>value</em>s of <code>s1</code> and <code>s2</code> is exactly equal to
* the <em>value</em> of <code>s3</code>.
*
* @return <code>s1+s2</code>: a spring representing <code>s1</code> and <code>s2</code> in series
*
* @see Spring
*/
public static
Spring sum(
Spring s1,
Spring s2) {
return new
SumSpring(
s1,
s2);
}
/**
* Returns <code>max(s1, s2)</code>: a spring whose value is always greater than (or equal to)
* the values of both <code>s1</code> and <code>s2</code>.
*
* @return <code>max(s1, s2)</code>: a spring whose value is always greater than (or equal to)
* the values of both <code>s1</code> and <code>s2</code>
* @see Spring
*/
public static
Spring max(
Spring s1,
Spring s2) {
return new
MaxSpring(
s1,
s2);
}
// Remove these, they're not used often and can be created using minus -
// as per these implementations.
/*pp*/ static
Spring difference(
Spring s1,
Spring s2) {
return
sum(
s1,
minus(
s2));
}
/*
public static Spring min(Spring s1, Spring s2) {
return minus(max(minus(s1), minus(s2)));
}
*/
/**
* Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em>
* and <em>value</em> properties are each multiples of the properties of the
* argument spring, <code>s</code>. Minimum and maximum properties are
* swapped when <code>factor</code> is negative (in accordance with the
* rules of interval arithmetic).
* <p>
* When factor is, for example, 0.5f the result represents 'the mid-point'
* of its input - an operation that is useful for centering components in
* a container.
*
* @param s the spring to scale
* @param factor amount to scale by.
* @return a spring whose properties are those of the input spring <code>s</code>
* multiplied by <code>factor</code>
* @throws NullPointerException if <code>s</code> is null
* @since 1.5
*/
public static
Spring scale(
Spring s, float
factor) {
checkArg(
s);
return new
ScaleSpring(
s,
factor);
}
/**
* Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em>
* and <em>value</em> properties are defined by the widths of the <em>minimumSize</em>,
* <em>preferredSize</em>, <em>maximumSize</em> and <em>size</em> properties
* of the supplied component. The returned spring is a 'wrapper' implementation
* whose methods call the appropriate size methods of the supplied component.
* The minimum, preferred, maximum and value properties of the returned spring
* therefore report the current state of the appropriate properties in the
* component and track them as they change.
*
* @param c Component used for calculating size
* @return a spring whose properties are defined by the horizontal component
* of the component's size methods.
* @throws NullPointerException if <code>c</code> is null
* @since 1.5
*/
public static
Spring width(
Component c) {
checkArg(
c);
return new
WidthSpring(
c);
}
/**
* Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em>
* and <em>value</em> properties are defined by the heights of the <em>minimumSize</em>,
* <em>preferredSize</em>, <em>maximumSize</em> and <em>size</em> properties
* of the supplied component. The returned spring is a 'wrapper' implementation
* whose methods call the appropriate size methods of the supplied component.
* The minimum, preferred, maximum and value properties of the returned spring
* therefore report the current state of the appropriate properties in the
* component and track them as they change.
*
* @param c Component used for calculating size
* @return a spring whose properties are defined by the vertical component
* of the component's size methods.
* @throws NullPointerException if <code>c</code> is null
* @since 1.5
*/
public static
Spring height(
Component c) {
checkArg(
c);
return new
HeightSpring(
c);
}
/**
* If <code>s</code> is null, this throws an NullPointerException.
*/
private static void
checkArg(
Object s) {
if (
s == null) {
throw new
NullPointerException("Argument must not be null");
}
}
}