Created attachment 27123 [details]
The problematic Excel file

When HSSFPatriarch store more than 1023 drawing objects with list validation enabled, POI will generate a problematic excel (xls) which will move the (total drawing objects % 1024) th drawing object to the validation cell when click on the validation enabled cell.

Here is the example code to produce this bug:
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import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

import javax.imageio.ImageIO;

import org.apache.poi.hssf.usermodel.DVConstraint;
import org.apache.poi.hssf.usermodel.HSSFClientAnchor;
import org.apache.poi.hssf.usermodel.HSSFDataValidation;
import org.apache.poi.hssf.usermodel.HSSFPatriarch;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.ClientAnchor;
import org.apache.poi.ss.util.CellRangeAddressList;

public final class TestCase {
    public static void main (String[] args) {
        HSSFWorkbook wb = null;
        try {
            wb = new HSSFWorkbook();
            HSSFSheet sheet = wb.createSheet();
            InputStream iconFileStream = TestCase.class.getResourceAsStream("icon.png");
            // Convert to PNG image format in case the image is not in PNG
            BufferedImage iconImage = ImageIO.read(iconFileStream);
            ByteArrayOutputStream iconByteStream = new ByteArrayOutputStream();
            ImageIO.write(iconImage, "PNG", iconByteStream);
            HSSFPatriarch patriarch = sheet.createDrawingPatriarch();

            // Use the same image for the demo
            int imgIndex = wb.addPicture(iconByteStream.toByteArray(), HSSFWorkbook.PICTURE_TYPE_PNG);
            for (int i = 0; i < 1023; ++i) {
                HSSFClientAnchor anchor = new HSSFClientAnchor(0, 0, 0, 0, (short) 1, i, (short) 2, i + 1);
                anchor.setAnchorType(ClientAnchor.MOVE_DONT_RESIZE);
                patriarch.createPicture(anchor, imgIndex);
            }
            // The 1024+ th image
            for (int i = 0; i < 1; ++i) {
                HSSFClientAnchor anchor = new HSSFClientAnchor(0, 0, 0, 0, (short) 3, i, (short) 4, i + 1);
                anchor.setAnchorType(ClientAnchor.MOVE_DONT_RESIZE);
                patriarch.createPicture(anchor, imgIndex);
            }
            // Create validation for demo the bug
            DVConstraint listValidatorConstraint = DVConstraint.createExplicitListConstraint(new String [] { "Value 1" });
            HSSFDataValidation listValidator = new HSSFDataValidation(new CellRangeAddressList(0, 65535, 2, 2), listValidatorConstraint);
            sheet.addValidationData(listValidator);
            OutputStream fos = new FileOutputStream("problematic.xls");
            wb.write(fos);
            fos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
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When you click on the column C of the generated Excel file, the picture in B1 will move to the current position and the validation does not work.