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||done|
|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||done|
|Font handling for cells||tbe/dr||done|
|Cell styles (names, formatting)||dr||done|
|Column settings (format, width, outlines)||tbe/dr/kohei||in progress||outlines|
|Row settings (format, height, outlines)||tbe/dr/kohei||in progress||outlines|
|Rich text in cells||dr||done|
|Scheme fragment, scheme colors||dr||done|
|Cell formulas, array formulas, shared formulas||dr||in progress||function name mapping, shared formulas|
|Conditional formatting||kohei||in progress|
|External references/links||kohei||formula parser||parsing of externalLink fragments complete. The external link information is stored in ::oox::xls::ExtRefBuffer.|
|Print ranges, builtin defined names||dr||done|
|Page/print settings||dr/kohei||done||waiting on header/footer task to be completed.|
|Sheet/document view settings||dr||done|
|Cell hyperlinks||kohei||done||because a cell hyperlink is a in-cell text field object in Calc, as opposed to a cell property in Excel, a hyperlink will not get imported when the cell is a value cell.|
|Label ranges [reference]||skipped||MS Office 2007 seems to have dropped support for this feature.|
|Data validation||kohei||in progress|
|Web queries||kohei||formula parser||needs defined names, which requires formula parser.|
|Pivot tables||kohei||in progress|
|OLE objects, form controls||sj/dr|
|Auto filter, user filter||kohei||done||some incompatible bits present, so we have to be creative in importing Excel's autofilter items.|
- xl/workbook.xml contains externalReference tags that references relationship items in xl/_rels/workbook.xml.rels by rID.
- xl/_rels/workbook.xml.rels contains path(s) to external link fragments, that are usually xl/externalLinks/externalLink*.xml.
- xl/externalLinks/externalLink*.xml contains summary content information of the external book being referenced. It should provide enough information to display external cell's content. It also contains reference to the path to the external file by rID.
- xl/externalLinks/_rels/externalLink*.xml.rels contains the path to the external file, stored by rID.
Inside a cell that contains an external cell reference, the format is given
The UNO API for data validation is here.
There are 5 relevant sections to touch.
- /xl/worksheets/_rels/sheet?.xml.rels - contains the paths to query table properties fragments.
- /xl/queryTables/queryTable?.xml - contains query table properties, especially their name and associated connection IDs.
- /xl/_rels/workbook.xml.rels - contains the path to connections properties fragment.
- /xl/connections.xml - contains connections properties, such as URL.
- /xl/workbook.xml - defined names are used to associate a cell range to a query table by name.
The import strategy is to:
- Store the query table properties into query table container, with name as a key.
- Store the connections properties into connection container, with connection ID as a key.
- Parse a defined name and see if a query table for the same name exists.
- If yes, get the connection ID from the query table list.
- Get the connection properties by that ID from the connection list.
- Connect to the URL for data retrieval.
- /xl/workbook.xml - contains the IDs of pivot table caches and their relation IDs.
- /xl/_rels/workbook.xml.rels - contains paths to pivot table cache fragments and their IDs.
- /xl/worksheets/_rels/sheet?.xml.rels - contains path to pivot table xml fragment(s). Note that the source sheet fragment does not contain the relation ID to such pivot table fragment.
- /xl/pivotTables/pivotTable?.xml - contains the pivot table definitions.
- /xl/pivotTables/_rels/pivotTable?.xml.rels - contains the path to pivot table cache.
- /xl/pivotCache/pivotCacheDefinition?.xml - pivot cache definitions.
- /xl/pivotCache/_rels/pivotCacheDefinition?.xml.rels - contains the path to pivot cache records.
- /xl/pirovtCache/pivotCacheRecords?.xml - pivot cache records.