import java.awt.*;
import java.util.*;
/**
* A class representing a collection of constraints. Each constraint is
* of the form x +d <= y where
* x and y are variables and d is a non-negative
* constant.
* There should be no cyclic dependencies, such as
* x + 1 <= y,
* y + 1 <= x,
* since such dependencies obviously have no solution.
* Variables are implemented as integers.
* Constraint sets can be solved returning an object of
* class Solution.
* @see Solution
*/
public class Constraints
extends Printable
{
/**
* The font metrics used in these constraints.
*/
public final FontMetrics fm;
/**
* The number of variables in the constraint set.
*/
public int varCount;
/**
* The constraints on which variables are above which others.
*/
public ConstraintVector above;
/**
* The constraints on which variables are below which others.
*/
public ConstraintVector below;
/*
* Which variables are horizontal.
*/
private BitSet horizontal;
/*
* The font height.
*/
private int fontHeight;
/**
* Create a new constraint set.
* @param fm the font metrics to base all distances on.
*/
public Constraints (FontMetrics fm) {
this.fm = fm;
varCount = 0;
above = new ConstraintVector ();
below = new ConstraintVector ();
horizontal = new BitSet ();
fontHeight = fm.getMaxAscent () + fm.getMaxDescent ();
}
/**
* Print the constraint set (useful for debugging).
* @param p where to print to.
*/
public void print (Printer p) {
int i = 0;
while (i < this.varCount) {
p.printString ("[" + i + "] <= ");
p.print (this.above.get (i));
p.newLine ();
i = i+1;
}
}
/**
* Solve the constraint set.
* @return the solution.
*/
public Solution solve () {
return new Solution (this);
}
/**
* Create a new vertical variable.
* @return the new variable.
*/
public int newVVar () {
varCount = varCount + 1;
above.create ();
below.create ();
return varCount - 1;;
}
/**
* Create a new horizontal variable.
* @return the new variable.
*/
public int newHVar () {
horizontal.set (varCount);
return newVVar ();
}
/**
* Is this variable horizontal or vertical?
* @param x the variable.
* @return true iff the variable is horizontal.
*/
public boolean isHorizontal (int x) {
return horizontal.get (x);
}
/**
* Add a constraint x + 0 <= y
* @param x the lower variable
* @param y the higher variable
*/
public void gap0 (int x, int y) {
above.gap (0,x,y);
below.gap (0,y,x);
}
/**
* Add a constraint x + d <= y
* where d is a `small' gap (20% of the font height).
* @param x the lower variable
* @param y the higher variable
*/
public void gap1 (int x, int y) {
above.gap (fontHeight/5,x,y);
below.gap (fontHeight/5,y,x);
}
/**
* Add a constraint x + d <= y
* where d is a `large' gap (50% of the font height).
* @param x the lower variable
* @param y the higher variable
*/
public void gap2 (int x, int y) {
above.gap (fontHeight/2,x,y);
below.gap (fontHeight/2,y,x);
}
/**
* Add a constraint x + d <= y
* where d is the width of the string.
* @param s the string to measure
* @param x the lower variable
* @param y the higher variable
*/
public void gapStringWidth (String s, int x, int y) {
int d = fm.stringWidth (s) + (fontHeight/2);
above.gap (d,x,y);
below.gap (d,y,x);
}
/**
* Add a constraint x + d <= y
* where d is the height of the string.
* @param s the string to measure
* @param x the lower variable
* @param y the higher variable
*/
public void gapStringHeight (String s, int x, int y) {
above.gap (fontHeight,x,y);
below.gap (fontHeight,y,x);
}
}