Catch #REF! error - issue of a warning is necessary

Development
1

If a referenced cell is deleted (delete row, column, sheet) the referencing cells show #REF! - no warning is issued.
technically this is OK, but frustrating for users, as this error is often only detected much later and reconstruction of the sheet is cumbersome if possible at all.
Any ideas?

2

here is what Grok2 thinks …
Indeed, actions like deleting rows, columns, or entire sheets are common causes of #REF! errors, and implementing automatic checks in these scenarios makes a lot of sense. Here’s why and how this could be implemented:

Why Automatic Checks Are Necessary:

  • Data Integrity: Deleting parts of a spreadsheet can lead to loss of important data or references, which might not be immediately obvious to the user.

  • Prevent Data Loss: It ensures that users are aware of the impact of their actions, potentially preventing accidental data loss.

  • User Education: It educates users about the consequences of their actions, promoting better data management practices.

How to Implement Automatic Checks:

  1. Immediate Feedback:

    • Warning Dialog: Before the deletion action is finalized, show a warning dialog indicating that this action will result in #REF! errors. This could list how many formulas will be affected.

    • Preview Mode: Offer a preview of what the spreadsheet will look like after the deletion, highlighting cells that will become #REF!.

  2. Error Detection:

    • Real-time Scanning: As soon as the user selects to delete, scan all formulas in the workbook to see if any reference the cells about to be deleted.

    • Impact Assessment: Provide details on what will be affected, perhaps even specifying which sheets or types of formulas will be impacted.

  3. User Options:

    • Confirm or Cancel: Give users the choice to proceed with the deletion, knowing the consequences, or cancel the action.

    • Alternatives: Suggest alternatives like:

      • Moving data instead of deleting.
      • Using “Clear Contents” if only the data within cells needs to be removed, not the cells themselves.
      • Offering to update references automatically where possible.

  4. Advanced Features:

    • Undo Capability: Ensure users can undo the action easily if they proceed and realize there’s an issue.

    • Automatic Correction: For simpler cases, offer to automatically update formulas to avoid #REF! errors, e.g., by shifting references to the next valid cell.

  5. Integration with Existing Tools:

    • Combine with Trace Precedents/Dependents: Show users which formulas depend on the data they’re about to delete, leveraging existing tracing tools.

    • Error Checking: Integrate this check with the broader error-checking functionality of the spreadsheet software, perhaps with an option to run a full check after the operation.

Implementation Considerations:

  • Performance: Balance the thoroughness of the check with performance. Checking every single formula might be too intensive for very large spreadsheets, so consider a threshold or sample check.

  • User Experience: Ensure the warning or feedback doesn’t become overly intrusive. Users might still want to delete data even if it causes #REF! errors for a reason.

  • Customizability: Power users might want to disable these checks or adjust sensitivity; provide options for this in settings or through macros.

  • Education: Use this as an opportunity to teach users about spreadsheet management, perhaps with links to help resources.

By integrating automatic checks for #REF! errors specifically with delete actions, you can significantly enhance data integrity and user awareness, potentially preventing data loss and improving overall spreadsheet management.

3

Grok2 proposes this
Creating an extension for LibreOffice to check for #REF! errors when deleting rows, columns, or sheets involves several steps since we’re moving beyond simple macros into the realm of LibreOffice UNO (Universal Network Objects) API programming. Here’s an outline of how you might extend LibreOffice with Java to achieve this:

Step 1: Setup Environment

  • Install Apache NetBeans or your IDE of choice with support for Java and the LibreOffice SDK.
  • Download and set up the LibreOffice SDK.

Step 2: Create the Extension

Project Structure:

  • Descriptor: description.xml
  • Library: Your Java code will go here.
  • Registration: Addon.xcu or Dialog.xcu for registering your extension.

Java Code (simplified example):

Here’s how you might write the Java code to listen for delete events and check for errors:

import com.sun.star.beans.PropertyValue;
import com.sun.star.uno.UnoRuntime;
import com.sun.star.uno.XComponentContext;
import com.sun.star.lang.XMultiComponentFactory;
import com.sun.star.sheet.XSpreadsheetDocument;
import com.sun.star.sheet.XSpreadsheets;
import com.sun.star.container.XIndexAccess;
import com.sun.star.sheet.XSpreadsheet;
import com.sun.star.table.XCell;
import com.sun.star.table.XCellRange;
import com.sun.star.sheet.XCellRangeData;
import com.sun.star.sheet.XCellRangeFormula;
import com.sun.star.sheet.XSheetCellRange;
import com.sun.star.text.XTextRange;
import com.sun.star.frame.XController;
import com.sun.star.frame.XModel;
import com.sun.star.util.XModifyListener;
import com.sun.star.lang.EventObject;

public class ErrorChecker implements XModifyListener {
    private XComponentContext m_xContext;
    private XSpreadsheetDocument m_xDocument;

    public ErrorChecker(XComponentContext xContext, XSpreadsheetDocument xDoc) {
        this.m_xContext = xContext;
        this.m_xDocument = xDoc;
        // Register listener for document modifications
        XModel xModel = UnoRuntime.queryInterface(XModel.class, xDoc);
        xModel.addModifyListener(this);
    }

    @Override
    public void modified(EventObject event) {
        checkForREFErrors();
    }

    private void checkForREFErrors() {
        XController xController = m_xDocument.getCurrentController();
        XSpreadsheet xSheet = UnoRuntime.queryInterface(XSpreadsheet.class, xController.getActiveSheet());

        try {
            XCellRange xCellRange = UnoRuntime.queryInterface(XCellRange.class, xSheet);
            XCellRangeFormula xCellRangeFormula = UnoRuntime.queryInterface(XCellRangeFormula.class, xCellRange);
            String[][] formulas = xCellRangeFormula.getFormulaArray();

            StringBuilder errorMsg = new StringBuilder("The following cells contain #REF! errors:\n");
            boolean errorFound = false;

            for (int row = 0; row < formulas.length; row++) {
                for (int col = 0; col < formulas[row].length; col++) {
                    if (formulas[row][col] != null && formulas[row][col].contains("#REF!")) {
                        errorMsg.append(" - ").append(xSheet.getCellByPosition(col, row).getCellAddress()).append("\n");
                        errorFound = true;
                    }
                }
            }

            if (errorFound) {
                // Here you would typically show a dialog or use some UI component to notify the user
                System.out.println(errorMsg.toString()); // For demo, just print
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    // Main method for testing within an IDE or as part of extension deployment
    public static void main(String[] args) {
        // This part would be different in a real extension setup, where you'd get context from LibreOffice
    }
}

Step 3: Extension Deployment

  • description.xml: Describe your extension here, specifying version, dependencies, etc.
  • Addon.xcu: Register your service so it can be loaded when LibreOffice starts.
<oor:component-data xmlns:oor="http://openoffice.org/2001/registry" xmlns:xs="http://www.w3.org/2001/XMLSchema" oor:name="Addons" oor:package="org.openoffice.Office">
    <node oor:name="AddonUI">
        <node oor:name="OfficeMenuBar">
            <node oor:name="com.sun.star.sheet.SpreadsheetDocument">
                <prop oor:name="URL" oor:type="xs:string">
                    <value>/path/to/your/extension/ErrorChecker.class</value>
                </prop>
            </node>
        </node>
    </node>
</oor:component-data>

Step 4: Integration

  • You’ll need to integrate this with the actual event of deleting rows/columns/sheets. Since LibreOffice doesn’t have straightforward hooks for such actions, you might need to listen to document modifications and infer deletions from there, or you could extend the UI to include a custom delete button that triggers your check.

  • Use the XModifyListener interface to capture document changes. However, catching exact delete events might require more complex event handling or even modifying the source code of LibreOffice for precise control.

This example provides a conceptual framework rather than a complete, deployable extension. Creating an actual extension would require further integration with LibreOffice’s event system, UI design for user notifications, and packaging everything into an OXT file format for distribution.

4

I’m not exactly sure what’s the expected behavior here – do you want some kind of PostMessage notification when #REF! happens?

Either way, if you want to interact with the UNO API, see Using Python scripting in Collabora Online — SDK https://sdk.collaboraonline.com/ documentation – Java won’t work in the locked down jail where the LO code is executed.

5

A popup should warn the user that a #REF! condition happened.
Even in simple spreadsheets #REF! Errors are not necessarily detected in time to allow to correct the situation with UNDO.