nwalsh/saxon/Table.java

// Verbatim.java - Saxon extensions supporting DocBook verbatim environments

package com.nwalsh.saxon;

import java.util.Hashtable;
import org.xml.sax.*;
import org.w3c.dom.*;
import javax.xml.transform.TransformerException;
import com.icl.saxon.Controller;
import com.icl.saxon.expr.*;
import com.icl.saxon.om.*;
import com.icl.saxon.pattern.*;
import com.icl.saxon.Context;
import com.icl.saxon.tree.*;
import com.icl.saxon.functions.Extensions;

/**
 * <p>Saxon extensions supporting Tables</p>
 *
 * <p>$Id: Table.java,v 1.3 2006/04/27 08:26:47 xmldoc Exp $</p>
 *
 * <p>Copyright (C) 2000 Norman Walsh.</p>
 *
 * <p>This class provides a
 * <a href="http://saxon.sourceforge.net/">Saxon</a>
 * implementation of some code to adjust CALS Tables to HTML
 * Tables.</p>
 *
 * <p><b>Column Widths</b></p>
 * <p>The <tt>adjustColumnWidths</tt> method takes a result tree
 * fragment (assumed to contain the colgroup of an HTML Table)
 * and returns the result tree fragment with the column widths
 * adjusted to HTML terms.</p>
 *
 * <p><b>Convert Lengths</b></p>
 * <p>The <tt>convertLength</tt> method takes a length specification
 * of the form 9999.99xx (where "xx" is a unit) and returns that length
 * as an integral number of pixels. For convenience, percentage lengths
 * are returned unchanged.</p>
 * <p>The recognized units are: inches (in), centimeters (cm),
 * millimeters (mm), picas (pc, 1pc=12pt), points (pt), and pixels (px).
 * A number with no units is assumed to be pixels.</p>
 *
 * <p><b>Change Log:</b></p>
 * <dl>
 * <dt>1.0</dt>
 * <dd><p>Initial release.</p></dd>
 * </dl>
 *
 * @author Norman Walsh
 * <a href="mailto:ndw@nwalsh.com">ndw@nwalsh.com</a>
 *
 * @version $Id: Table.java,v 1.3 2006/04/27 08:26:47 xmldoc Exp $
 *
 */
public class Table {
  /** The number of pixels per inch */
  private static int pixelsPerInch = 96;

  /** The nominal table width (6in by default). */
  private static int nominalWidth = 6 * pixelsPerInch;

  /** The default table width (100% by default). */
  private static String tableWidth = "100%";

  /** Is this an FO stylesheet? */
  private static boolean foStylesheet = false;

  /** The hash used to associate units with a length in pixels. */
  protected static Hashtable unitHash = null;

  /**
   * <p>Constructor for Verbatim</p>
   *
   * <p>All of the methods are static, so the constructor does nothing.</p>
   */
  public Table() {
  }

  /** Initialize the internal hash table with proper values. */
  protected static void initializeHash() {
    unitHash = new Hashtable();
    unitHash.put("in", new Float(pixelsPerInch));
    unitHash.put("cm", new Float(pixelsPerInch / 2.54));
    unitHash.put("mm", new Float(pixelsPerInch / 25.4));
    unitHash.put("pc", new Float((pixelsPerInch / 72) * 12));
    unitHash.put("pt", new Float(pixelsPerInch / 72));
    unitHash.put("px", new Float(1));
  }

  /** Set the pixels-per-inch value. Only positive values are legal. */
  public static void setPixelsPerInch(int value) {
    if (value > 0) {
      pixelsPerInch = value;
      initializeHash();
    }
  }

  /** Return the current pixels-per-inch value. */
  public int getPixelsPerInch() {
    return pixelsPerInch;
  }

  /**
   * <p>Convert a length specification to a number of pixels.</p>
   *
   * <p>The specified length should be of the form [+/-]999.99xx,
   * where xx is a valid unit.</p>
   */
  public static int convertLength(String length) {
    // The format of length should be 999.999xx
    int sign = 1;
    String digits = "";
    String units = "";
    char lench[] = length.toCharArray();
    float flength = 0;
    boolean done = false;
    int pos = 0;
    float factor = 1;
    int pixels = 0;

    if (unitHash == null) {
      initializeHash();
    }

    if (lench[pos] == '+' || lench[pos] == '-') {
      if (lench[pos] == '-') {
	sign = -1;
      }
      pos++;
    }

    while (!done) {
      if (pos >= lench.length) {
	done = true;
      } else {
	if ((lench[pos] > '9' || lench[pos] < '0') && lench[pos] != '.') {
	  done = true;
	  units = length.substring(pos);
	} else {
	  digits += lench[pos++];
	}
      }
    }

    try {
      flength = Float.parseFloat(digits);
    } catch (NumberFormatException e) {
      System.out.println(digits + " is not a number; 1 used instead.");
      flength = 1;
    }

    Float f = null;

    if (!units.equals("")) {
      f = (Float) unitHash.get(units);
      if (f == null) {
	System.out.println(units + " is not a known unit; 1 used instead.");
	factor = 1;
      } else {
	factor = f.floatValue();
      }
    } else {
      factor = 1;
    }

    f = new Float(flength * factor);

    pixels = f.intValue() * sign;

    return pixels;
  }

  /**
   * <p>Find the string value of a stylesheet variable or parameter</p>
   *
   * <p>Returns the string value of <code>varName</code> in the current
   * <code>context</code>. Returns the empty string if the variable is
   * not defined.</p>
   *
   * @param context The current stylesheet context
   * @param varName The name of the variable (without the dollar sign)
   *
   * @return The string value of the variable
   */
  protected static String getVariable(Context context, String varName)
    throws TransformerException {
    Value variable = null;
    String varString = null;

    try {
      variable = Extensions.evaluate(context, "$" + varName);
      varString = variable.asString();
      return varString;
    } catch (IllegalArgumentException e) {
      System.out.println("Undefined variable: " + varName);
      return "";
    }
  }

  /**
   * <p>Setup the parameters associated with column width calculations</p>
   *
   * <p>This method queries the stylesheet for the variables
   * associated with table column widths. It is called automatically before
   * column widths are adjusted. The context is used to retrieve the values,
   * this allows templates to redefine these variables.</p>
   *
   * <p>The following variables are queried. If the variables do not
   * exist, builtin defaults will be used (but you may also get a bunch
   * of messages from the Java interpreter).</p>
   *
   * <dl>
   * <dt><code>nominal.table.width</code></dt>
   * <dd>The "normal" width for tables. This must be an absolute length.</dd>
   * <dt><code>table.width</code></dt>
   * <dd>The width for tables. This may be either an absolute
   * length or a percentage.</dd>
   * </dl>
   *
   * @param context The current stylesheet context
   *
   */
  private static void setupColumnWidths(Context context) {
    // Hardcoded defaults
    nominalWidth = 6 * pixelsPerInch;
    tableWidth = "100%";

    String varString = null;

    try {
      // Get the stylesheet type
      varString = getVariable(context, "stylesheet.result.type");
      foStylesheet = varString.equals("fo");

      // Get the nominal table width
      varString = getVariable(context, "nominal.table.width");
      nominalWidth = convertLength(varString);

      // Get the table width
      varString = getVariable(context, "table.width");
      tableWidth = varString;
    } catch (TransformerException e) {
      //nop, can't happen
    }
  }

  /**
   * <p>Adjust column widths in an HTML table.</p>
   *
   * <p>The specification of column widths in CALS (a relative width
   * plus an optional absolute width) are incompatible with HTML column
   * widths. This method adjusts CALS column width specifiers in an
   * attempt to produce equivalent HTML specifiers.</p>
   *
   * <p>In order for this method to work, the CALS width specifications
   * should be placed in the "width" attribute of the &lt;col>s within
   * a &lt;colgroup>. Then the colgroup result tree fragment is passed
   * to this method.</p>
   *
   * <p>This method makes use of two parameters from the XSL stylesheet
   * that calls it: <code>nominal.table.width</code> and
   * <code>table.width</code>. The value of <code>nominal.table.width</code>
   * must be an absolute distance. The value of <code>table.width</code>
   * can be either absolute or relative.</p>
   *
   * <p>Presented with a mixture of relative and
   * absolute lengths, the table width is used to calculate
   * appropriate values. If the <code>table.width</code> is relative,
   * the nominal width is used for this calculation.</p>
   *
   * <p>There are three possible combinations of values:</p>
   *
   * <ol>
   * <li>There are no relative widths; in this case the absolute widths
   * are used in the HTML table.</li>
   * <li>There are no absolute widths; in this case the relative widths
   * are used in the HTML table.</li>
   * <li>There are a mixture of absolute and relative widths:
   *   <ol>
   *     <li>If the table width is absolute, all widths become absolute.</li>
   *     <li>If the table width is relative, make all the widths absolute
   *         relative to the nominal table width then turn them all
   *         back into relative widths.</li>
   *   </ol>
   * </li>
   * </ol>
   *
   * @param context The stylesheet context; supplied automatically by Saxon
   * @param rtf_ns The result tree fragment containing the colgroup.
   *
   * @return The result tree fragment containing the adjusted colgroup.
   *
   */
  public static NodeSetValue adjustColumnWidths (Context context,
						 NodeSetValue rtf_ns) {

    FragmentValue rtf = (FragmentValue) rtf_ns;

    setupColumnWidths(context);

    try {
      Controller controller = context.getController();
      NamePool namePool = controller.getNamePool();

      ColumnScanEmitter csEmitter = new ColumnScanEmitter(namePool);
      rtf.replay(csEmitter);

      int numColumns = csEmitter.columnCount();
      String widths[] = csEmitter.columnWidths();

      float relTotal = 0;
      float relParts[] = new float[numColumns];

      float absTotal = 0;
      float absParts[] = new float[numColumns];

      for (int count = 0; count < numColumns; count++) {
	String width = widths[count];

	int pos = width.indexOf("*");
	if (pos >= 0) {
	  String relPart = width.substring(0, pos);
	  String absPart = width.substring(pos+1);

	  try {
	    float rel = Float.parseFloat(relPart);
	    relTotal += rel;
	    relParts[count] = rel;
	  } catch (NumberFormatException e) {
	    System.out.println(relPart + " is not a valid relative unit.");
	  }

	  int pixels = 0;
	  if (absPart != null && !absPart.equals("")) {
	    pixels = convertLength(absPart);
	  }

	  absTotal += pixels;
	  absParts[count] = pixels;
	} else {
	  relParts[count] = 0;

	  int pixels = 0;
	  if (width != null && !width.equals("")) {
	    pixels = convertLength(width);
	  }

	  absTotal += pixels;
	  absParts[count] = pixels;
	}
      }

      // Ok, now we have the relative widths and absolute widths in
      // two parallel arrays.
      //
      // - If there are no relative widths, output the absolute widths
      // - If there are no absolute widths, output the relative widths
      // - If there are a mixture of relative and absolute widths,
      //   - If the table width is absolute, turn these all into absolute
      //     widths.
      //   - If the table width is relative, turn these all into absolute
      //     widths in the nominalWidth and then turn them back into
      //     percentages.

      if (relTotal == 0) {
	for (int count = 0; count < numColumns; count++) {
	  Float f = new Float(absParts[count]);
	  if (foStylesheet) {
	    int pixels = f.intValue();
	    float inches = (float) pixels / pixelsPerInch;
	    widths[count] = inches + "in";
	  } else {
	    widths[count] = Integer.toString(f.intValue());
	  }
	}
      } else if (absTotal == 0) {
	for (int count = 0; count < numColumns; count++) {
	  float rel = relParts[count] / relTotal * 100;
	  Float f = new Float(rel);
	  widths[count] = Integer.toString(f.intValue());
	}
	widths = correctRoundingError(widths);
      } else {
	int pixelWidth = nominalWidth;

	if (tableWidth.indexOf("%") <= 0) {
	  pixelWidth = convertLength(tableWidth);
	}

	if (pixelWidth <= absTotal) {
	  System.out.println("Table is wider than table width.");
	} else {
	  pixelWidth -= absTotal;
	}

	absTotal = 0;
	for (int count = 0; count < numColumns; count++) {
	  float rel = relParts[count] / relTotal * pixelWidth;
	  relParts[count] = rel + absParts[count];
	  absTotal += rel + absParts[count];
	}

	if (tableWidth.indexOf("%") <= 0) {
	  for (int count = 0; count < numColumns; count++) {
	    Float f = new Float(relParts[count]);
	    if (foStylesheet) {
	      int pixels = f.intValue();
	      float inches = (float) pixels / pixelsPerInch;
	      widths[count] = inches + "in";
	    } else {
	      widths[count] = Integer.toString(f.intValue());
	    }
	  }
	} else {
	  for (int count = 0; count < numColumns; count++) {
	    float rel = relParts[count] / absTotal * 100;
	    Float f = new Float(rel);
	    widths[count] = Integer.toString(f.intValue());
	  }
	  widths = correctRoundingError(widths);
	}
      }

      ColumnUpdateEmitter cuEmitter = new ColumnUpdateEmitter(controller,
							      namePool,
							      widths);

      rtf.replay(cuEmitter);
      return cuEmitter.getResultTreeFragment();
    } catch (TransformerException e) {
      // This "can't" happen.
      System.out.println("Transformer Exception in adjustColumnWidths");
      return rtf;
    }
  }

  /**
   * Correct rounding errors introduced in calculating the width of each
   * column. Make sure they sum to 100% in the end.
   */
  protected static String[] correctRoundingError(String widths[]) {
    int totalWidth = 0;

    for (int count = 0; count < widths.length; count++) {
      try {
	int width = Integer.parseInt(widths[count]);
	totalWidth += width;
      } catch (NumberFormatException nfe) {
	// nop; "can't happen"
      }
    }

    float totalError = 100 - totalWidth;
    float columnError = totalError / widths.length;
    float error = 0;

    for (int count = 0; count < widths.length; count++) {
      try {
	int width = Integer.parseInt(widths[count]);
	error = error + columnError;
	if (error >= 1.0) {
	  int adj = (int) Math.round(Math.floor(error));
	  error = error - (float) Math.floor(error);
	  width = width + adj;
	  widths[count] = Integer.toString(width) + "%";
	} else {
	  widths[count] = Integer.toString(width) + "%";
	}
      } catch (NumberFormatException nfe) {
	// nop; "can't happen"
      }
    }

    return widths;
  }
}