/**
@page working_with_macros Working with VBA Macros

@tableofcontents

This section explains how to add a VBA file containing functions or macros to
an libxlsxwriter workbook.

@dontinclude macro.c
@skipline include
@until    return
@skipline }


@image html macros.png

@section ww_macros_xlsm_format The Excel XLSM file format

An Excel `xlsm` file is exactly the same as an `xlsx` file except that is
contains an additional `vbaProject.bin` file which contains functions and/or
macros. Excel uses a different extension to differentiate between the two file
formats since files containing macros are usually subject to additional
security checks.


@section ww_macros_include How VBA macros are included in libxlsxwriter files

The `vbaProject.bin` file is a binary OLE COM container. This was the format
used in older `xls` versions of Excel prior to Excel 2007. Unlike all of the
other components of an xlsx/xlsm file the data isn't stored in XML
format. Instead the functions and macros as stored as a pre-parsed binary
format. As such it wouldn't be feasible to define macros and create a
`vbaProject.bin` file from scratch (at least not in the remaining lifespan and
interest levels of the author).

Instead a workaround is used to extract `vbaProject.bin` files from existing
xlsm files and then add these to libxlsxwriter generated files.


@section ww_macros_extract The vba_extract.py utility

The `vba_extract.py` Python utility is used to extract the `vbaProject.bin`
binary from an Excel 2007+ xlsm file. The utility is included in the
libxlsxwriter examples directory:

    $ python examples/vba_extract.py macro_file.xlsm
    Extracted: vbaProject.bin

You can also install `vba_extract.py` into your system path by installing the
Python xlsxwriter module:

    $ pip install xlsxwriter
    ...
    $ vba_extract.py
    Utility to extract a vbaProject.bin binary from an
    Excel 2007+ xlsm macro file ...


@section ww_macros_adding Adding the VBA macros to a libxlsxwriter file

Once the `vbaProject.bin` file has been extracted it can be added to the
libxlsxwriter workbook using the `workbook_add_vba_project()` function:

@code
    workbook_add_vba_project(workbook, "./vbaProject.bin");
@endcode

@note The name doesn't have to be `vbaProject.bin`. Any suitable path/name for
an existing VBA bin file will do.

If the VBA file contains functions you can then refer to them in calculations
using `worksheet_write_formula()`:

@code
    worksheet_write_formula(0, 0, "=MyMortgageCalc(200000, 25)")
@endcode

Excel files that contain functions and macros should use an `xlsm` extension
or else Excel will complain and possibly not open the file:

@code
    lxw_workbook *workbook = new_workbook("macro.xlsm");
@endcode


@section ww_macros_codenames Setting the VBA codenames

VBA macros generally refer to workbook and worksheet objects. If the VBA
codenames aren't specified explicitly then libxlsxwriter will use the Excel
defaults of `ThisWorkbook` and `Sheet1`, `Sheet2` etc.

If the macro uses other codenames you can set them using the
`workbook_set_vba_name()` and `worksheet_set_vba_name()` functions as follows:

@code
    // Set the VBA codenames for the workbook and any worksheets.
    workbook_set_vba_name (workbook,  "MyWorkbook");
    worksheet_set_vba_name(worksheet, "MySheet1");
    worksheet_set_vba_name(worksheet, "MySheet2");
@endcode

@note This step is particularly important for macros created with non-English
versions of Excel.

You can find the names that are used in the VBA editor or by unzipping the
`xlsm` file and grepping the files. The following shows how to do that using
[libxml's xmllint](http://xmlsoft.org/xmllint.html) to format the XML for
clarity:

    $ unzip myfile.xlsm -d myfile
    $ xmllint --format `find myfile -name "*.xml" | xargs` | grep "Pr.*codeName"

      <workbookPr codeName="MyWorkbook" defaultThemeVersion="124226"/>
      <sheetPr codeName="MySheet1"/>


@section ww_macros_debugging What to do if it doesn't work

The libxlsxwriter test suite contains several tests to ensure that this feature
works and there is a working example as shown above. However, there is no
guarantee that it will work in all cases. Some effort may be required and some
knowledge of VBA will certainly help. If things don't work out here are some
things to try:

1. Start with a simple macro file, ensure that it works and then add complexity.

2. Check the code names that macros use to refer to the workbook and
   worksheets (see the previous section above). In general VBA uses a code
   name of `ThisWorkbook` to refer to the current workbook and the sheet name
   (such as `Sheet1`) to refer to the worksheets. These are the defaults used
   by libxlsxwriter. If the macro uses other names, or the macro was extracted
   from an non-English language version of Excel, then you can specify the
   appropriate names using the `workbook_set_vba_name()` and
   `worksheet_set_vba_name()` functions:
   @code
       // Set the VBA codenames for the workbook and any worksheets.
       workbook_set_vba_name (workbook,  "MyWorkbook");
       worksheet_set_vba_name(worksheet, "MySheet1");
       worksheet_set_vba_name(worksheet, "MySheet2");
   @endcode

3. Try to extract the macros from an Excel 2007 file. The method should work
   with macros from later versions (it was also tested with Excel 2010
   macros). However there may be features in the macro files of more recent
   version of Excel that aren't backward compatible.


Next: @ref examples


*/
