User Story

As an app developer, I want to use the Excel "hidden number format" (;; in Keikai so that I can hide cell content for presentation or sensitive data purposes while preserving the underlying data.

Acceptance Criteria

1. When a cell's custom number format is set to {;;;}

   , its content is not visible in the sheet view, matching Excel's behavior.

2. The underlying cell value remains intact and is accessible via formulas or when the cell is edited.
3. When importing Excel files that use the ;;; format, Keikai correctly hides the content as expected.
4. Exported files from Keikai retain the ;;; format, ensuring round-trip fidelity with Excel.

Details

• Excel supports a special custom number format using three semicolons (;;, which hides all cell content visually, but does not delete or alter the underlying data. This feature is often called the "hidden number format" or "cell hiding format."
• obvious root cause

          case 4:
          default:
              posNumFmt = parts.get(0);
              negNumFmt = parts.get(1);
              zeroNumFmt = parts.get(2);
              textFmt = parts.get(3);
              textFmt.setSectionFourTextFormat(true);// KEIKAI-243
              break;
          }
  

• example test file keikai-820.xlsx

Current Result

java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
	at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
	at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
	at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248)
	at java.base/java.util.Objects.checkIndex(Objects.java:372)
	at java.base/java.util.ArrayList.get(ArrayList.java:459)
	at org.zkoss.poi.ss.format.CellFormat.<init>(CellFormat.java:229)
	at org.zkoss.poi.ss.format.CellFormat.getInstance(CellFormat.java:172)
	at io.keikai.model.impl.sys.FormatEngineImpl.getCellFormat(FormatEngineImpl.java:79)
	at io.keikaiex.model.sys.FormatEngineEx.getCellFormat(FormatEngineEx.java:46)
	at io.keikai.model.impl.sys.FormatEngineImpl.format0(FormatEngineImpl.java:98)
	at io.keikai.model.impl.sys.FormatEngineImpl.format(FormatEngineImpl.java:70)
	at io.keikai.ui.impl.CellFormatHelper.getFormatResult(CellFormatHelper.java:997)
	at io.keikai.ui.SpreadsheetCtrlImpl.getCellAttr(SpreadsheetCtrlImpl.java:543)
	at io.keikai.ui.SpreadsheetCtrlImpl.getRangeAttrs(SpreadsheetCtrlImpl.java:390)
	at io.keikai.ui.Spreadsheet.createActiveRange(Spreadsheet.java:2040)
	at io.keikai.ui.Spreadsheet.renderProperties(Spreadsheet.java:1980)

Use case

This special format might have its special purposes:

• Data Management : you may want to keep certain data hidden from view while still retaining it for calculations or further processing.
• Error Handling : It can also be applied to cells that might produce errors (like ) to prevent those errors from displaying #VALUE!