General discussion about 0.96 priorities

@Pankraty @b0bi79

Firstly, let’s wait for 0.95 to be adopted widely and wait for the first wave of regressions to be sorted out.

Then the big tasks I would like to focus on for 0.96 are:

• Pivot table formats: We need to explicitly list all the pivot table formats and have test files for each individual format, as well as combinations of them. At the moment I have only combinations and makes the reverse-engineering of them almost impossible.
• Calculation engine context, for evaluation of e.g. =ROW() #1415
• Formula repository / caching: #1201 addresses this already.
• XLLoadOptions to set some stuff, e.g. user-specified locale (#1367). Discussion at #1407
• Support for external references, even if only partial support. The workbooks at least should not break.
• Refactor pivot tables into pivot sources + pivot tables
• Support pivot table calculated formulas (dependent on previous point).
• Protection: Align workbook and worksheet protection. Implement newer protection methods.
• Improve loading of cell data. At the moment we parse the OpenXML Cell’s text value, and then ToString() it immediately. I think we should delay the parsing of the text value until the cell’s value has to be recalculated.

Before any of you just start writing code, let’s just chat. I have some PRs and branches locally that already address some of these issues.

[Pankraty]

I was thinking about refactoring saving/loading logic.

1. First, detach saving/loading from XLWorkbook class into separate classes implementing IXLWorkbookReader and IXLWorkbookWriter.
2. Then, provide the alternative implementations
   • XLInMemoryWorkbookReader, XLInMemoryWorkbookWriter - basically, the current implementation, fully initializing the entire workbook in memory. Maybe it has to take care of #912 also.
   • XLReadOnlyWorkbookReader - a fast implementation with lazy loading of needed sections in a read-only mode. It may help with #781, #1345, and many other scenarios where we only need to read some data and do not really care about formats, data validations, etc. This cannot work without accessing the original stream by design.
   • XLStrictModeWorkbookReader, XLStrictModeWorkbookWriter - to operate with workbooks using strict mode (#1378).

This would also open a window for supporting different formats, maybe sometime in the future.

[timunie]

Hi ClosedXML Team,

first of all this is a great library and it makes my life really easier 👍 . For me it would be a great enhancement if I could pick from named predefined styles. I read a template with custom CellStyles in it and want to apply those. I think there is already a ticket open for this #1290 .

Happy coding Tim