When we are missing external dependencies and OCIO_INSTALL_EXT_PACKAGES has been set to MISSING or ALL , we use CMake ExternalProject to build these locally. This works but tends to be hard to manage correctly with modern CMake library that can export a number of targets as well as custom commands and probably other items. We also have a lot of manual CMake flags passing from the main project to the external ones, that are easy to miss.
An example of this would be OpenEXR which export more than 5 different targets we have to manually create, at the risk of getting out of sync when something changes upstream. Another case is pybind11 which export custom commands like pybind11_add_module which we cannot currently use in the build because it will not be there when pybind11 has been built locally I believe.
For well behaved modern CMake dependencies, it may be good to look into FetchContent instead, which behave similar to add_subdirectory and make the integration easier.
When we are missing external dependencies and
OCIO_INSTALL_EXT_PACKAGEShas been set toMISSINGorALL, we use CMake ExternalProject to build these locally. This works but tends to be hard to manage correctly with modern CMake library that can export a number of targets as well as custom commands and probably other items. We also have a lot of manual CMake flags passing from the main project to the external ones, that are easy to miss.An example of this would be OpenEXR which export more than 5 different targets we have to manually create, at the risk of getting out of sync when something changes upstream. Another case is pybind11 which export custom commands like
pybind11_add_modulewhich we cannot currently use in the build because it will not be there when pybind11 has been built locally I believe.For well behaved modern CMake dependencies, it may be good to look into FetchContent instead, which behave similar to
add_subdirectoryand make the integration easier.