SpreadsheetML is the XML format used by Microsoft Excel 2007 and that is part of the Office Open XML specification.
- 1 SpreadsheetML Basics
- 2 Sample Files
- 3 Implementation Strategy
- 4 Code Organization
- 5 Development
- 6 See Also
A SpreadsheetML document is described at the top level by a workbook part ( /xl/workbook.xml ). The type of the work book type is
The workbook part contains document's metadata and one or more sheets. Each sheet can be a worksheet, a chart sheet, or a dialog sheet.
Both strings and formulas are stored in shared tables to avoid redundant storage and speed file I/O's.
Convenient locations to download sample files are here
Eventually, the code handling SpreadsheetML import will merge with the existing Excel binary filter. As such, the new code needs to be designed with this in mind. It's always desirable to understand how the existing binary filter works when implementing the XML filter to make the future merging work less painful.
Source files for handling the SpreadsheetML format are located in inc/oox/xls and source/xls under module oox. A good place to start tracing the code would be ExcelFilter::Import and follow the calls it makes.
A substream in the XML package is called "fragment", and each fragment has an associated *fragment.hxx header file. For instance, the code for loading of the workbook.xml fragment is found in workbookfragment.hxx, and so on.
A nested element is called "context", and, like the fragments, each context has an associated *context.hxx. For instance, the code for parsing the <sheetData> element is found in sheetdatacontext.hxx.
The term workbook in this context refers to an entire document which includes worksheets and other document metadata, whereas the term worksheet refers to each individual sheet in the workbook.
The existing binary Excel filter is located in sc/source/filter/(inc|excel)/xi(page|view).(c|h)xx. The XclImpTabViewSettings class handles importing sheet's view settings, which corresponds to worksheet/sheetViews context in the XML format.
The UNO interface code is found in sc/source/ui/uno.
Workbook-wide global data are stored in GlobalData (struct), and handled by GlobalDataHelper (class) which holds reference to the GlobalData instance. All major classes should be derived from GlobalDataHelper to ensure availability of globals in all places.
GlobalData holds reference to ImportBase instance in order to be able to create new fragment handlers.
Different buffers hold the imported data from the fragments if it is needed later, e.g. the SharedStringsBuffer (sharedstringsbuffer.hxx) and the StylesBuffer (stylesbuffer.hxx). These buffers are always part of the GlobalDataHelper.
It's important to be familar with the member methods of this class, because they are also available in most of XLSX import classes.
Handles loading of workbook.xml fragment. It loads the associated relationship file (xl/_rels/workbook.xml.rels) in the constructor.
In most cases the fragment handler will handle all nested contexts by itself to increase performance. For this, some helper classes have been implemented that do all needed work to deal with nested contexts (ContextHelper, FragmentBase, and ContextBase respectively in contexthelper.hxx, excelfragmentbase.hxx, and excelcontextbase.hxx). In general, for implementing a new fragment or context handler, the interface of the ContextHelper class from contexthelper.hxx has to be implemented. The classes FragmentBase (excelfragmentbase.hxx) and ContextBase (excelcontextbase.hxx) already provide default implementations of all virtual functions, but a derived class is free to implement them as well.
Holds three string data for ID, Type and Target (need more info).
converts strings to addresses and ranges, and tracks invalid addresses (e.g. a not-importable cell at address ZZZ1000000). Later, this information will be used to generate a "Imported document contains data outside of sheet limits" warning box after loading. Header: addressconverter.hxx
provides basic unit conversion, including font dependent stuff such as calculating column width from a specific number of characters. Header: unitconverter.hxx
|Framework, fragment handling||cl/dr||done|
|Workbook, worksheet fragment, sheet names||tbe/dr||in progress||do not insert default sheets (issue 74668)|
|Simple cell contents (values, strings)||dr||in progress||error cells|
|Shared strings fragment||dr||done|
|Simple cell formatting (alignment, protection, borders, fill)||dr||done|
|Builtin number formats||dr||in progress||missing locales (issue 29949)|
|Font handling for cells||tbe/dr||in progress||asian/complex scripts (issue 74754)|
|Cell styles (names, formatting)||dr||done|
|Column settings (format, width, outlines)||tbe/dr/kohei||in progress||outlines, hidden, column width from font (issue 75447)|
|Row settings (format, height, outlines)||tbe/dr/kohei||in progress||outlines, hidden, row borders (issue 74667)|
|Rich text in cells||dr||done|
|Scheme fragment, scheme colors||dr||done|
|Cell formulas, array formulas||jody/kohei|
|Link table, external sheets||jody/kohei|
|Print ranges, builtin defined names||jody/kohei|
|Page/print settings||kohei||in progress|
|Sheet/document view settings||kohei||in progress||not possible to set view settings during import; probably needs to create a buffer class to store imported view settings, and apply them after the import.|
|OLE objects, form controls||sj/dr|
|Auto filter, user filter|
Refer to class XclPageData which is the data structure used by the existing binary filter. Here is the page for Calc's sheet properties.