A recent blog post talked about how to build and manage dependencies with CMake and FetchContent. The example that they used was a simple GUI application using the SFML multimedia libraries and the Dear ImGui widget toolkit using the corresponding wrapper library. For comparison let's do the same with Meson.
The tl/dr version is that all you need is to install Meson, check out this repository and start the build. Meson will automatically download all dependencies as source, build them from scratch and create a single statically linked final executable. SFML's source archive contains a bunch of prebuilt dependencies for OpenAL and the like. Those are not used, everything is compiled from original sources. A total of 11 subprojects are used including things like libpng, Freetype and Flac.
They are downloaded from Meson's WrapDB dependency provider/package manager service. which combines upstream tarballs with user submitted Meson build definitions. The only exception is stb. It has no releases, instead it is expected to be used directly from Git. As WrapDB only provides actual releases, this dependency needs to be checked out from a custom Git repo. This is entirely transparent to the user, the only change is that the wrap file specifying where the dependency comes from points to a different place.
If you actually try to compile the code you might face some issues. It has only been properly tested on Windows. It will probably work on Linux and most definitely won't work on macOS. At the time of writing GNU's web mirror has an expired certificate so downloading Freetype's release tarball will fail. You can work around it by downloading it by hand and placing it in the subprojects/packagecache directory. The build of SFML might also fail as the code uses auto_ptr, which has been removed from some stdlibs. This has been fixed in master (but not in the way you might have expected) but the fix has not made it to a release yet.
What does it look like?
This picture shows the app running. To the left you can also see all the dependencies that were loaded during the build. It also tells you why people should do proper release tarballs rather than relying on Github's autogenerated ones. Since every project's files are named v1.0.0.zip, the risk of name collision is high.
What's the difference between the two?
CMake has a single flat project space (or at least that is how it is being used here) which is used like this:
I.e. "download the given file, extract it in the current directory (whatever it may be) and enter it as if it was our own code". This is "easy" but problematic in that the subproject may change its parent project in interesting ways that usually lead to debugging and hair pulling.
In Meson every subproject is compiled in its own isolated sandbox. They can only communicate in specific, well defined and secured channels. This makes it easy to generate projects that can be built from source on Windows/macOS/Android/etc and which use system dependencies on Linux transparently. This equals less hassle for everyone involved.
There are other advantages as well. Meson provides a builtin option for determining whether a project should build its libraries shared or static. This option can be set on the command line per subproject. The sample application project is set up to build everything statically for convenience. However one of the dependencies, OpenAL, is LGPL, so for final distributions you'll probably need to build it as a shared library. This can be achieved with the following command:
After this only the OpenAL dependency is built as a shared library whereas everything else is still static. As this is a builtin, no project needs to write their own options, flags and settings to select whether to build shared or static libraries. Better yet, no end user has to hunt around to discover whether the option to change is FOO_BUILD_SHARED, FOO_ENABLE_SHARED, FOO_SHARED_LIBS, SHARED_FOO, or something else.