Swing/LineNumber のバックアップの現在との差分(No.5)

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class LineNumberView extends JComponent {
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  private static final int MARGIN = 5;
  private final JTextArea textArea;
  private final FontMetrics fontMetrics;
  // private final int topInset;
  private final int fontAscent;
  private final int fontHeight;
  private final int fontDescent;
  private final int fontLeading;

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#screenshot
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  public LineNumberView(JTextArea textArea) {
    this.textArea = textArea;
    Font font = textArea.getFont();
    fontMetrics = getFontMetrics(font);
    fontHeight = fontMetrics.getHeight();
    fontAscent = fontMetrics.getAscent();
    fontDescent = fontMetrics.getDescent();
    fontLeading = fontMetrics.getLeading();
    // topInset = textArea.getInsets().top;

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**サンプルコード [#caf6edeb]
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#code{{
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 class LineNumberView extends JComponent {
   private static final int MARGIN = 5;
   private final JTextArea text;
   private final FontMetrics fontMetrics;
   private final int topInset;
   private final int fontAscent;
   private final int fontHeight;
   public LineNumberView(JTextArea textArea) {
     text        = textArea;
     fontMetrics = getFontMetrics(text.getFont());
     fontHeight  = fontMetrics.getHeight();
     fontAscent  = fontMetrics.getAscent();
     topInset    = text.getInsets().top;
     text.getDocument().addDocumentListener(new DocumentListener() {
       public void insertUpdate(DocumentEvent e) {
         repaint();
       }
       public void removeUpdate(DocumentEvent e) {
         repaint();
       }
       public void changedUpdate(DocumentEvent e) {}
     });
     text.addComponentListener(new ComponentAdapter() {
       public void componentResized(ComponentEvent e) {
         revalidate();
         repaint();
       }
     });
     setBorder(BorderFactory.createMatteBorder(0, 0, 0, 1, Color.GRAY));
   }
   private int getComponentWidth() {
     Document doc  = text.getDocument();
     Element root  = doc.getDefaultRootElement();
     int lineCount = root.getElementIndex(doc.getLength());
     int maxDigits = Math.max(3, String.valueOf(lineCount).length());
     return maxDigits*fontMetrics.stringWidth("0")+MARGIN*2;
   }
   private int getLineAtPoint(int y) {
     Element root = text.getDocument().getDefaultRootElement();
     int pos = text.viewToModel(new Point(0, y));
     return root.getElementIndex(pos);
   }
   public Dimension getPreferredSize() {
     return new Dimension(getComponentWidth(), text.getHeight());
   }
   public void paintComponent(Graphics g) {
     Rectangle clip = g.getClipBounds();
     g.setColor(getBackground());
     g.fillRect(clip.x, clip.y, clip.width, clip.height);
     g.setColor(getForeground());
     int base  = clip.y - topInset;
     int start = getLineAtPoint(base);
     int end   = getLineAtPoint(base+clip.height);
     int y = topInset-fontHeight+fontAscent+start*fontHeight;
     for(int i=start;i<=end;i++) {
       String text = String.valueOf(i+1);
       int x = getComponentWidth()-MARGIN-fontMetrics.stringWidth(text);
       y = y + fontHeight;
       g.drawString(text, x, y);
     }
   }
 }
    textArea.getDocument().addDocumentListener(new DocumentListener() {
      @Override public void insertUpdate(DocumentEvent e) {
        repaint();
      }
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      @Override public void removeUpdate(DocumentEvent e) {
        repaint();
      }
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      @Override public void changedUpdate(DocumentEvent e) {
        // repaint();
      }
    });
    textArea.addComponentListener(new ComponentAdapter() {
      @Override public void componentResized(ComponentEvent e) {
        revalidate();
        repaint();
      }
    });
    Insets i = textArea.getInsets();
    setBorder(BorderFactory.createCompoundBorder(
      BorderFactory.createMatteBorder(0, 0, 0, 1, Color.GRAY),
      BorderFactory.createEmptyBorder(i.top, MARGIN, i.bottom, MARGIN - 1)));
    setOpaque(true);
    setBackground(Color.WHITE);
    setFont(font);
  }
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  private int getComponentWidth() {
    Document doc = textArea.getDocument();
    Element root = doc.getDefaultRootElement();
    int lineCount = root.getElementIndex(doc.getLength());
    int maxDigits = Math.max(3, String.valueOf(lineCount).length());
    Insets i = getInsets();
    return maxDigits * fontMetrics.stringWidth("0") + i.left + i.right;
    // return 48;
  }
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  private int getLineAtPoint(int y) {
    Element root = textArea.getDocument().getDefaultRootElement();
    int pos = textArea.viewToModel(new Point(0, y));
    return root.getElementIndex(pos);
  }
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  @Override public Dimension getPreferredSize() {
    return new Dimension(getComponentWidth(), textArea.getHeight());
  }
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  @Override protected void paintComponent(Graphics g) {
    g.setColor(getBackground());
    Rectangle clip = g.getClipBounds();
    g.fillRect(clip.x, clip.y, clip.width, clip.height);
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    g.setColor(getForeground());
    int base = clip.y;
    int start = getLineAtPoint(base);
    int end = getLineAtPoint(base + clip.height);
    int y = start * fontHeight;
    int rmg = getInsets().right;
    for (int i = start; i <= end; i++) {
      String text = String.valueOf(i + 1);
      int x = getComponentWidth() - rmg - fontMetrics.stringWidth(text);
      y += fontAscent;
      g.drawString(text, x, y);
      y += fontDescent + fontLeading;
    }
  }
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}
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