Dave Jarvis' Repositories

/*
 * Copyright 2020 White Magic Software, Ltd.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  o Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 *  o Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.scrivenvar.preview;

import com.scrivenvar.util.BoundedCache;
import org.apache.commons.io.FilenameUtils;
import org.w3c.dom.Element;
import org.xhtmlrenderer.extend.ReplacedElement;
import org.xhtmlrenderer.extend.ReplacedElementFactory;
import org.xhtmlrenderer.extend.UserAgentCallback;
import org.xhtmlrenderer.layout.LayoutContext;
import org.xhtmlrenderer.render.BlockBox;
import org.xhtmlrenderer.simple.extend.FormSubmissionListener;
import org.xhtmlrenderer.swing.ImageReplacedElement;

import java.awt.image.BufferedImage;
import java.util.Map;
import java.util.function.Function;

import static com.scrivenvar.StatusBarNotifier.alert;
import static com.scrivenvar.preview.SvgRasterizer.rasterize;
import static com.scrivenvar.processors.markdown.tex.TeXNode.HTML_TEX;

/**
 * Responsible for running {@link SvgRasterizer} on SVG images detected within
 * a document to transform them into rasterized versions.
 */
public class SvgReplacedElementFactory implements ReplacedElementFactory {

  /**
   * Prevent instantiation until needed.
   */
  private static class MathRendererContainer {
    private static final MathRenderer INSTANCE = new MathRenderer();
  }

  /**
   * Returns the singleton instance for rendering math symbols.
   *
   * @return A non-null instance, loaded, configured, and ready to render math.
   */
  public static MathRenderer getInstance() {
    return MathRendererContainer.INSTANCE;
  }

  /**
   * SVG filename extension maps to an SVG image element.
   */
  private static final String SVG_FILE = "svg";

  private static final String HTML_IMAGE = "img";
  private static final String HTML_IMAGE_SRC = "src";

  /**
   * A bounded cache that removes the oldest image if the maximum number of
   * cached images has been reached. This constrains the number of images
   * loaded into memory.
   */
  private final Map<String, BufferedImage> mImageCache =
      new BoundedCache<>( 150 );

  @Override
  public ReplacedElement createReplacedElement(
      final LayoutContext c,
      final BlockBox box,
      final UserAgentCallback uac,
      final int cssWidth,
      final int cssHeight ) {
    BufferedImage image = null;
    final var e = box.getElement();

    if( e != null ) {
      try {
        final var nodeName = e.getNodeName();

        if( HTML_IMAGE.equals( nodeName ) ) {
          final var src = e.getAttribute( HTML_IMAGE_SRC );
          final var ext = FilenameUtils.getExtension( src );

          if( SVG_FILE.equalsIgnoreCase( ext ) ) {
            image = getCachedImage(
                src, svg -> rasterize( svg, box.getContentWidth() ) );
          }
        }
        else if( HTML_TEX.equals( nodeName ) ) {
          // Convert the TeX element to a raster graphic if not yet cached.
          final var src = e.getTextContent();
          image = getCachedImage(
              src, __ -> rasterize( getInstance().render( src ) )
          );
        }
      } catch( final Exception ex ) {
        alert( ex );
      }
    }

    if( image != null ) {
      final var w = image.getWidth( null );
      final var h = image.getHeight( null );

      return new ImageReplacedElement( image, w, h );
    }

    return null;
  }

  @Override
  public void reset() {
  }

  @Override
  public void remove( final Element e ) {
  }

  @Override
  public void setFormSubmissionListener( FormSubmissionListener listener ) {
  }

  /**
   * Returns an image associated with a string; the string's pre-computed
   * hash code is returned as the string value, making this operation very
   * quick to return the corresponding {@link BufferedImage}.
   *
   * @param src        The source used for the key into the image cache.
   * @param rasterizer {@link Function} to call to rasterize an image.
   * @return The image that corresponds to the given source string.
   */
  private BufferedImage getCachedImage(
      final String src, final Function<String, BufferedImage> rasterizer ) {
    return mImageCache.computeIfAbsent( src, __ -> rasterizer.apply( src ) );
  }
}