wxWidgets/docs/tech/tn0021.txt
2005-09-16 16:18:32 +00:00

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How to add a new wxUSE_XXX preprocessor constant
================================================
0. 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.
1. 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.
2. Required files update
------------------------
Assuming wxUSE_FOO is used on all platforms, the following must be done:
a) update 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).
b) update other setup.h files
Currently include/wx/univ/setup.h and setup.h_vms are not automatically
updated so please update them manually (or modify the update-setup-h script
to take care of them...).
c) update 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 valye 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 togetherw 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.
3. Documentation
----------------
Currently wxUSE_XXXs are not documented, except for a few important global ones
which are in docs/latex/wx/cppconst.tex. So normally there is nothing to do
(but this could change in the future).
=== EOF ===
Author: VZ
Version: $Id$