I've made a DEB package of an C++ app that I've created. I want this app to use resources in the "data" directory, which, in my tests (for convenience), is in the same location that the program binary, and I call it from inside the code by its relative path. In the Debian OS there are standard locations to put the data files in (something like /usr/share/...), and other location to put the binaries in (probably /usr/bin). I'd not like to put the paths hard-coded in my program, I think its a better practice to access an image by "data/img.png" than "/usr/share/.../data/img.png". All the GNU classic programs respect the directories structure, and I imagine they do it in a good manner. I tried to use dpkg to find out the structure of the apps, but that didn't help me. Is there a better way that I'm doing to do this?
PS: I also want my code to be portable to Windows (cross-platform) avoiding using workarounds like "if WIN32" as much as possible.
In your Debian package you should indeed install your data in /usr/share/. When accessing your data, you should use the XDG standard, which states that $XDG_DATA_DIRS is a colon-separated list of data directories to search (also, "if $XDG_DATA_DIRS is either not set or empty, a value equal to /usr/local/share/:/usr/share/ should be used.").