pdfbox-trunk/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/interactive/annotation/handlers/PDLineAppearanceHandler.java
/*
 * Copyright 2018 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.pdfbox.pdmodel.interactive.annotation.handlers;

import java.io.IOException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.font.PDFont;
import org.apache.pdfbox.pdmodel.graphics.color.PDColor;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotation;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotationLine;
import org.apache.pdfbox.pdmodel.PDAppearanceContentStream;
import org.apache.pdfbox.pdmodel.PDDocument;
import static org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotationLine.LE_NONE;
import org.apache.pdfbox.util.Matrix;

/**
 *
 */
public class PDLineAppearanceHandler extends PDAbstractAppearanceHandler
{
    private static final Log LOG = LogFactory.getLog(PDLineAppearanceHandler.class);

    static final int FONT_SIZE = 9;

    public PDLineAppearanceHandler(PDAnnotation annotation)
    {
        super(annotation);
    }

    public PDLineAppearanceHandler(PDAnnotation annotation, PDDocument document)
    {
        super(annotation, document);
    }

    @Override
    public void generateNormalAppearance()
    {
        PDAnnotationLine annotation = (PDAnnotationLine) getAnnotation();
        PDRectangle rect = annotation.getRectangle();
        if (rect == null)
        {
            return;
        }
        float[] pathsArray = annotation.getLine();
        if (pathsArray == null)
        {
            return;
        }
        AnnotationBorder ab = AnnotationBorder.getAnnotationBorder(annotation, annotation.getBorderStyle());
        PDColor color = annotation.getColor();
        if (color == null || color.getComponents().length == 0)
        {
            return;
        }
        float ll = annotation.getLeaderLineLength();
        float lle = annotation.getLeaderLineExtensionLength();
        float llo = annotation.getLeaderLineOffsetLength();

        // Adjust rectangle even if not empty, see PLPDF.com-MarkupAnnotations.pdf
        float minX = Float.MAX_VALUE;
        float minY = Float.MAX_VALUE;
        float maxX = Float.MIN_VALUE;
        float maxY = Float.MIN_VALUE;
        for (int i = 0; i < pathsArray.length / 2; ++i)
        {
            float x = pathsArray[i * 2];
            float y = pathsArray[i * 2 + 1];
            minX = Math.min(minX, x);
            minY = Math.min(minY, y);
            maxX = Math.max(maxX, x);
            maxY = Math.max(maxY, y);
        }

        // Leader lines
        if (ll < 0)
        {
            // /LLO and /LLE go in the same direction as /LL
            llo = -llo;
            lle = -lle;
        }

        // observed with diagonal line of AnnotationSample.Standard.pdf
        // for line endings, very small widths must be treated as size 1.
        // However the border of the line ending shapes is not drawn.
        float lineEndingSize = (ab.width < 1e-5) ? 1 : ab.width;

        // add/subtract with, font height, and arrows
        // arrow length is 9 * width at about 30° => 10 * width seems to be enough
        // but need to consider /LL, /LLE and /LLO too
        //TODO find better way to calculate padding
        float max = Math.max(lineEndingSize * 10, Math.abs(llo+ll+lle));
        rect.setLowerLeftX(Math.min(minX - max, rect.getLowerLeftX()));
        rect.setLowerLeftY(Math.min(minY - max, rect.getLowerLeftY()));
        rect.setUpperRightX(Math.max(maxX + max, rect.getUpperRightX()));
        rect.setUpperRightY(Math.max(maxY + max, rect.getUpperRightY()));

        annotation.setRectangle(rect);

        try (PDAppearanceContentStream cs = getNormalAppearanceAsContentStream())
        {
            setOpacity(cs, annotation.getConstantOpacity());

            // Tested with Adobe Reader:
            // text is written first (TODO)
            // width 0 is used by Adobe as such (but results in a visible line in rendering)
            // empty color array results in an invisible line ("n" operator) but the rest is visible
            // empty content is like no caption

            boolean hasStroke = cs.setStrokingColorOnDemand(color);

            if (ab.dashArray != null)
            {
                cs.setLineDashPattern(ab.dashArray, 0);
            }
            cs.setLineWidth(ab.width);

            float x1 = pathsArray[0];
            float y1 = pathsArray[1];
            float x2 = pathsArray[2];
            float y2 = pathsArray[3];

            // if there are leader lines, then the /L coordinates represent
            // the endpoints of the leader lines rather than the endpoints of the line itself.
            // so for us, llo + ll is the vertical offset for the line.
            float y = llo + ll;

            String contents = annotation.getContents();
            if (contents == null)
            {
                contents = "";
            }

            cs.saveGraphicsState();
            double angle = Math.atan2(y2 - y1, x2 - x1);
            cs.transform(Matrix.getRotateInstance(angle, x1, y1));
            float lineLength = (float) Math.sqrt(((x2 - x1) * (x2 - x1)) + ((y2 - y1) * (y2 - y1)));

            // Leader lines
            cs.moveTo(0, llo);
            cs.lineTo(0, llo + ll + lle);
            cs.moveTo(lineLength, llo);
            cs.lineTo(lineLength, llo + ll + lle);

            if (annotation.hasCaption() && !contents.isEmpty())
            {
                // Note that Adobe places the text as a caption even if /CP is not set
                // when the text is so long that it would cross arrows, but we ignore this for now
                // and stick to the specification.

                PDFont font = getDefaultFont();
                // TODO: support newlines!!!!!
                // see https://www.pdfill.com/example/pdf_commenting_new.pdf
                float contentLength = 0;
                try
                {
                    contentLength = font.getStringWidth(annotation.getContents()) / 1000 * FONT_SIZE;

                    //TODO How to decide the size of the font?
                    // 9 seems to be standard, but if the text doesn't fit, a scaling is done
                    // see AnnotationSample.Standard.pdf, diagonal line
                }
                catch (IllegalArgumentException ex)
                {
                    // Adobe Reader displays placeholders instead
                    LOG.error("line text '" + annotation.getContents() + "' can't be shown", ex);
                }
                float xOffset = (lineLength - contentLength) / 2;
                float yOffset;

                String captionPositioning = annotation.getCaptionPositioning();

                // draw the line horizontally, using the rotation CTM to get to correct final position
                // that's the easiest way to calculate the positions for the line before and after inline caption
                if (SHORT_STYLES.contains(annotation.getStartPointEndingStyle()))
                {
                    cs.moveTo(lineEndingSize, y);
                }
                else
                {
                    cs.moveTo(0, y);
                }
                if ("Top".equals(captionPositioning))
                {
                    // this arbitrary number is from Adobe
                    yOffset = 1.908f;
                }
                else
                {
                    // Inline
                    // this arbitrary number is from Adobe
                    yOffset = -2.6f;

                    cs.lineTo(xOffset - lineEndingSize, y);
                    cs.moveTo(lineLength - xOffset + lineEndingSize, y);
                }
                if (SHORT_STYLES.contains(annotation.getEndPointEndingStyle()))
                {
                    cs.lineTo(lineLength - lineEndingSize, y);
                }
                else
                {
                    cs.lineTo(lineLength, y);
                }
                cs.drawShape(lineEndingSize, hasStroke, false);

                // /CO entry (caption offset)
                float captionHorizontalOffset = annotation.getCaptionHorizontalOffset();
                float captionVerticalOffset = annotation.getCaptionVerticalOffset();

                // check contentLength so we don't show if there was trouble before
                if (contentLength > 0)
                {
                    cs.beginText();
                    cs.setFont(font, FONT_SIZE);
                    cs.newLineAtOffset(xOffset + captionHorizontalOffset, 
                                       y + yOffset + captionVerticalOffset);
                    cs.showText(annotation.getContents());
                    cs.endText();
                }

                if (Float.compare(captionVerticalOffset, 0) != 0)
                {
                    // Adobe paints vertical bar to the caption
                    cs.moveTo(0 + lineLength / 2, y);
                    cs.lineTo(0 + lineLength / 2, y + captionVerticalOffset);
                    cs.drawShape(lineEndingSize, hasStroke, false);
                }
            }
            else
            {
                if (SHORT_STYLES.contains(annotation.getStartPointEndingStyle()))
                {
                    cs.moveTo(lineEndingSize, y);
                }
                else
                {
                    cs.moveTo(0, y);
                }
                if (SHORT_STYLES.contains(annotation.getEndPointEndingStyle()))
                {
                    cs.lineTo(lineLength - lineEndingSize, y);
                }
                else
                {
                    cs.lineTo(lineLength, y);
                }
                cs.drawShape(lineEndingSize, hasStroke, false);
            }
            cs.restoreGraphicsState();
        
            // paint the styles here and not before showing the text, or the text would appear
            // with the interior color
            boolean hasBackground = cs.setNonStrokingColorOnDemand(annotation.getInteriorColor());

            // observed with diagonal line of file AnnotationSample.Standard.pdf
            // when width is very small, the border of the line ending shapes 
            // is not drawn.
            if (ab.width < 1e-5)
            {
                hasStroke = false;
            }

            // check for LE_NONE only needed to avoid q cm Q for that case
            if (!LE_NONE.equals(annotation.getStartPointEndingStyle()))
            {
                cs.saveGraphicsState();
                if (ANGLED_STYLES.contains(annotation.getStartPointEndingStyle()))
                {
                    cs.transform(Matrix.getRotateInstance(angle, x1, y1));
                    drawStyle(annotation.getStartPointEndingStyle(), cs, 0, y, lineEndingSize, hasStroke, hasBackground, false);
                }
                else
                {
                    // Support of non-angled styles is more difficult than in the other handlers
                    // because the lines do not always go from (x1,y1) to (x2,y2) due to the leader lines
                    // when the "y" value above is not 0.
                    // We use the angle we already know and the distance y to translate to the new coordinate.
                    float xx1 = x1 - (float) (y * Math.sin(angle));
                    float yy1 = y1 + (float) (y * Math.cos(angle));
                    drawStyle(annotation.getStartPointEndingStyle(), cs, xx1, yy1, lineEndingSize, hasStroke, hasBackground, false);
                }
                cs.restoreGraphicsState();
            }

            // check for LE_NONE only needed to avoid q cm Q for that case
            if (!LE_NONE.equals(annotation.getEndPointEndingStyle()))
            {
                // save / restore not needed because it's the last one
                if (ANGLED_STYLES.contains(annotation.getEndPointEndingStyle()))
                {
                    cs.transform(Matrix.getRotateInstance(angle, x2, y2));
                    drawStyle(annotation.getEndPointEndingStyle(), cs, 0, y, lineEndingSize, hasStroke, hasBackground, true);
                }
                else
                {
                    // Support of non-angled styles is more difficult than in the other handlers
                    // because the lines do not always go from (x1,y1) to (x2,y2) due to the leader lines
                    // when the "y" value above is not 0.
                    // We use the angle we already know and the distance y to translate to the new coordinate.
                    float xx2 = x2 - (float) (y * Math.sin(angle));
                    float yy2 = y2 + (float) (y * Math.cos(angle));
                    drawStyle(annotation.getEndPointEndingStyle(), cs, xx2, yy2, lineEndingSize, hasStroke, hasBackground, true);
                }
            }
        }
        catch (IOException ex)
        {
            LOG.error(ex);
        }
    }

    @Override
    public void generateRolloverAppearance()
    {
        // No rollover appearance generated
    }

    @Override
    public void generateDownAppearance()
    {
        // No down appearance generated
    }
}
