Program: 3863
Project: 3863
Buggy source:
private void initializePainters(){
  setBackgroundPainter(new Painter(){
    @Override public void paint(    Graphics2D g,    Object object,    int width,    int height){
      Shape mainPanelShape=getShape();
      Area panelArea=new Area(mainPanelShape);
      Point bottomLocation=SwingUtilities.convertPoint(mainPanel,bottomPanel.getLocation(),LibrarySharePanel.this);
      Area bottomArea=new Area(new Rectangle2D.Float(0,bottomLocation.y,getWidth(),1000));
      bottomArea.intersect(panelArea);
      Graphics2D g2=(Graphics2D)g.create();
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
      g2.setRenderingHint(RenderingHints.KEY_RENDERING,RenderingHints.VALUE_RENDER_SPEED);
      g2.setColor(Color.WHITE);
      g2.fill(panelArea);
      if (bottomPanel.isVisible()) {
        bottomGradient=new GradientPaint(0,bottomLocation.y,bottomPanelTopGradient,0,bottomLocation.y + bottomPanel.getHeight(),bottomPanelBottomGradient);
        g2.setPaint(bottomGradient);
        g2.fill(bottomArea);
        g2.setColor(dividerColor);
        Rectangle panelBounds=mainPanelShape.getBounds();
        g2.drawLine(panelBounds.x,bottomLocation.y,panelBounds.x + panelBounds.width,bottomLocation.y);
      }
      if (signInPanel.isVisible()) {
        g2.setColor(dividerColor);
        Rectangle panelBounds=mainPanelShape.getBounds();
        Point signInLocation=SwingUtilities.convertPoint(mainPanel,signInPanel.getLocation(),LibrarySharePanel.this);
        g2.drawLine(panelBounds.x,signInLocation.y,panelBounds.x + panelBounds.width,signInLocation.y);
      }
      g2.setColor(borderColor);
      g2.setStroke(new BasicStroke(2));
      g2.draw(mainPanelShape);
      g2.setStroke(new BasicStroke(1));
      g2.draw(mainPanelShape);
      g2.translate(1,1);
      g2.draw(mainPanelShape);
      g2.dispose();
    }
  }
);
}

Fixed version (ground truth):
private void initializePainters(){
  setBackgroundPainter(new Painter(){
    @Override public void paint(    Graphics2D g,    Object object,    int width,    int height){
      Shape mainPanelShape=getShape();
      Area panelArea=new Area(mainPanelShape);
      Point bottomLocation=SwingUtilities.convertPoint(mainPanel,bottomPanel.getLocation(),LibrarySharePanel.this);
      Area bottomArea=new Area(new Rectangle2D.Float(0,bottomLocation.y,getWidth(),1000));
      bottomArea.intersect(panelArea);
      Graphics2D g2=(Graphics2D)g.create();
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
      g2.setRenderingHint(RenderingHints.KEY_RENDERING,RenderingHints.VALUE_RENDER_SPEED);
      g2.setColor(Color.WHITE);
      g2.fill(panelArea);
      if (bottomPanel.isVisible()) {
        bottomGradient=new GradientPaint(0,bottomLocation.y,bottomPanelTopGradient,0,bottomLocation.y + bottomPanel.getHeight(),bottomPanelBottomGradient);
        g2.setPaint(bottomGradient);
        g2.fill(bottomArea);
        g2.setColor(dividerColor);
        Rectangle panelBounds=mainPanelShape.getBounds();
        g2.drawLine(panelBounds.x,bottomLocation.y,panelBounds.x + panelBounds.width,bottomLocation.y);
      }
      if (signInPanel.isVisible()) {
        g2.setColor(dividerColor);
        Rectangle panelBounds=mainPanelShape.getBounds();
        Point signInLocation=SwingUtilities.convertPoint(mainPanel,signInPanel.getLocation(),LibrarySharePanel.this);
        g2.drawLine(panelBounds.x,signInLocation.y,panelBounds.x + panelBounds.width,signInLocation.y);
      }
      g2.setColor(borderColor);
      g2.setStroke(new BasicStroke(2));
      Shape originalClip=g2.getClip();
      g2.setClip(originalClip.getBounds().x,originalClip.getBounds().y,10,10);
      g2.draw(mainPanelShape);
      g2.setClip(originalClip);
      g2.setStroke(new BasicStroke(1));
      g2.draw(mainPanelShape);
      g2.translate(1,1);
      g2.draw(mainPanelShape);
      g2.dispose();
    }
  }
);
}