cmake_modules.md

+Various cmake modules are used by the flair build system. They are located in [this directory](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/tree/main/cmake-modules).
+
+You will find some explanations of what they do here. But the best way to understand them is to read them!
+
+# [ArchDir.cmake](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/blob/main/cmake-modules/ArchDir.cmake)
+
+Retrieves the arch name from the toolchain file (*toolchain.cmake*). It is used to install files in the correct folders, and to check if a lib, demo or tool is compatible with a specific architecture or not.
+
+It also checks if host architecture is i686, as it is not supported.
+
+# [ColoredMessage.cmake](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/blob/main/cmake-modules/ColoredMessage.cmake)
+
+Defines some cmake functions to have colored messages.
+
+# [FindXenomai.cmake](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/blob/main/cmake-modules/FindXenomai.cmake)
+
+Find xenomai lib and defines some variables useful for cmake.
+
+# [GlobalCmakeFlair.cmake](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/blob/main/cmake-modules/GlobalCmakeFlair.cmake)
+
+reimplements some cmake built in functions to add extra functionalities
+
+* **ADD_EXECUTABLE**:
+  * add a message to display architecture 
+  * check if *$HOME/.ssh/config* have some hosts defined (see [here](Setup-your-computer#configure-ssh-hosts-optional)). In this case add a custom_target to cmake, to copy the executable with ssh. The custom target is called *delivery_root_ADDRESS_PATH*, with address the target address and path the destination path. 
+  * copy demos binaries. To enable this functionality, you need to add *SET(FLAIR_DEMO_DEST_DIR yourproject)* to your *CMakeLists.txt*, see this [example](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/blob/main/demos/CircleFollower/uav/CMakeLists.txt). Files will be copied to *$FLAIR_ROOT/flair-install/bin/demos/${ARCH_DIR}/yourproject*
+
+* **ADD_LIBRARY**:
+  * add a message to display architecture.
+  * add compile info in a .h (used by libs constructor), see [in FlairMeta](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/blob/main/lib/FlairMeta/src/UavFactory.cpp) for example.
+
+* **INSTALL**:
+  * copy resources files (scripts and xml files for the demos). Resources files are placed in the *resources* dir, and inside an arch dir. See for example in the [CircleFollower demo](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/tree/main/demos/CircleFollower/uav/resources). These files are not overwritten if they already exist. To enable this functionality, you need to add *SET(FLAIR_RESOURCE_FILES_DEST_DIR yourproject)* to your *CMakeLists.txt*, see this [example](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/blob/main/demos/CircleFollower/uav/CMakeLists.txt). Files will be copied to *$FLAIR_ROOT/flair-install/bin/demos/${ARCH_DIR}/yourproject*
+
+# [FlairUseFile.cmake](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/blob/main/cmake-modules/FlairUseFile.cmake)
+
+Used by demos/tools, it helps adding include dirs and libraries for programs using flair.
+
+It performs some checks:
+* presence of libxml2 in the toolchain
+* presence of xenomai in the toolchain
+* gcc version (must be >= 4.3)
+* presence of a flair-hds directory. For Heudiasyc users, see [here](hds-users)
+
+Needed include dirs and libraries are determined using some boolean variables:
+* **FLAIR_USE_SIMULATOR**
+* **FLAIR_USE_VRPN**
+* **FLAIR_USE_GPS**
+* **FLAIR_USE_VISION_FILTER**
+* **FLAIR_USE_SENSOR_ACTUATOR**
+* **FLAIR_USE_FILTER**
+* **FLAIR_USE_META**
+
+You have to set these variables to true in your *CMakeLists.txt*, if you need need these functionalities.
+
+In return, *FlairUseFile.cmake* will fill 3 variables:
+* **${FLAIR_INCLUDE_DIR}**: list of needed include dirs
+* **${FLAIR_LIBRARIES_RT}**: list of needed libraries for real time (xenomai)
+* **${FLAIR_LIBRARIES_NRT}**: list of needed libraries for non real time
+
+Take a look at CircleFollower demo [CMakeLists.txt](https://gitlab.utc.fr/uav-hds/flair/flair-src/-/blob/main/demos/CircleFollower/uav/CMakeLists.txt) file to see how it is used.