wxWidgets/docs/contributing/how-to-add-new-wxUSE_XXX.md

How to add a new wxUSE_XXX preprocessor constant

Purpose

Detailed description of what needs to be done when you want to add a new wxUSE_XXX compilation flag. The text below assumes you need new wxUSE_FOO.

Overview

wxWidgets uses wxUSE_XXX macros for conditionally compiling in (or not) optional components. In general, whenever a new non critical (i.e. not absolutely required by important parts of the library) class Foo is added it should use its own wxUSE_FOO compilation flag.

wxUSE_FOO must be always defined and have value of 0 or 1. Be careful with testing for it in wx/foo.h: don't do it at the very beginning of the file because then wxUSE_FOO would be not defined at all if the user directly includes wx/foo.h, include "wx/defs.h" before testing for wxUSE_FOO.

Files to update

The following files need to be modified when adding a new wxUSE_FOO:

• include/wx/setup_inc.h

  This file contains all common wxUSE_XXXs, and is used to update wxMSW, wxMac setup.h and Unix setup.h.in using build/update-setup-h. Please try to add the new define in a logical place (i.e. near any related ones) and write a detailed comment explaining what does it do and why would you want to turn it on/off. Choose the appropriate default value: this should be usually 1 but can be 0 if there are some problems preventing the use of Foo by default (e.g. it requires installation of some non standard 3rd party libraries). After changing this file, run the update-setup-h script (this is probably better done on a Unix machine although it should work under Cygwin too).

• include/wx/msw/setup_inc.h for MSW-specific options

  This file contains MSW-specific options, so if the new option is only used under MSW, add it here instead of include/wx/setup_inc.h. The rest of the instructions is the same as above.

• include/wx/chkconf.h

  Add the check for wxUSE_FOO definedness in the corresponding (base or GUI) section. Please keep the alphabetic order.

  If there are any dependencies, i.e. wxUSE_FOO requires wxUSE_BAR and wxUSE_BAZ, check for thme here too.

• include/wx/msw/chkconf.h for MSW-specific options

  These options won't be defined for the other ports, so shouldn't be added to the common include/wx/chkconf.h but to this file instead.

• configure.in

  Here you need to add DEFAULT_wxUSE_FOO define. It should be added in the block beginning after WX_ARG_CACHE_INIT line and should default to "no" for if DEBUG_CONFIGURE = 1 branch (this is used for absolutely minimal builds) and the same as default value in setup_inc.h in the "else" branch.

  You also need to add a WX_ARG_ENABLE (or, if new functionality can be reasonably described as support for a 3rd party library, WX_ARG_WITH) line together with all the existing WX_ARG_ENABLEs.

  If you have a sample/foo which should be only built when wxUSE_FOO==1, then only add it to the SAMPLES_SUBDIRS if wxUSE_FOO=yes in configure.

• build/cmake/options.cmake

  To include the option in CMake, add a new line in the appropriate section of options.cmake.

   wx_option(wxUSE_FOO "enable FOO")
  

  As an optional third parameter you may specify OFF when the option should be disabled by default.

• docs/doxygen/mainpages/const_wxusedef.h

  Add a brief description of the new constant.