Version Information Compile-time and run-time version checks. Cairo has a three-part version number scheme. In this scheme, we use even vs. odd numbers to distinguish fixed points in the software vs. in-progress development, (such as from git instead of a tar file, or as a "snapshot" tar file as opposed to a "release" tar file). _____ Major. Always 1, until we invent a new scheme. / ___ Minor. Even/Odd = Release/Snapshot (tar files) or Branch/Head (git) | / _ Micro. Even/Odd = Tar-file/git | | / 1.0.0 Here are a few examples of versions that one might see. Releases -------- 1.0.0 - A major release 1.0.2 - A subsequent maintenance release 1.2.0 - Another major release Snapshots --------- 1.1.2 - A snapshot (working toward the 1.2.0 release) In-progress development (eg. from git) -------------------------------------- 1.0.1 - Development on a maintenance branch (toward 1.0.2 release) 1.1.1 - Development on head (toward 1.1.2 snapshot and 1.2.0 release) The API/ABI compatibility guarantees for various versions are as follows. First, let's assume some cairo-using application code that is successfully using the API/ABI "from" one version of cairo. Then let's ask the question whether this same code can be moved "to" the API/ABI of another version of cairo. Moving from a release to any later version (release, snapshot, development) is always guaranteed to provide compatibility. Moving from a snapshot to any later version is not guaranteed to provide compatibility, since snapshots may introduce new API that ends up being removed before the next release. Moving from an in-development version (odd micro component) to any later version is not guaranteed to provide compatibility. In fact, there's not even a guarantee that the code will even continue to work with the same in-development version number. This is because these numbers don't correspond to any fixed state of the software, but rather the many states between snapshots and releases. Cairo provides the ability to examine the version at either compile-time or run-time and in both a human-readable form as well as an encoded form suitable for direct comparison. Cairo also provides the macro CAIRO_VERSION_ENCODE() to perform the encoding. Compile-time ------------ CAIRO_VERSION_STRING Human-readable CAIRO_VERSION Encoded, suitable for comparison Run-time -------- cairo_version_string() Human-readable cairo_version() Encoded, suitable for comparison For example, checking that the cairo version is greater than or equal to 1.0.0 could be achieved at compile-time or run-time as follows: ##if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1, 0, 0) printf ("Compiling with suitable cairo version: %s\n", %CAIRO_VERSION_STRING); ##endif if (cairo_version() >= CAIRO_VERSION_ENCODE(1, 0, 0)) printf ("Running with suitable cairo version: %s\n", cairo_version_string ()); The version of cairo available at compile-time, encoded using CAIRO_VERSION_ENCODE(). The major component of the version of cairo available at compile-time. The minor component of the version of cairo available at compile-time. The micro component of the version of cairo available at compile-time. A human-readable string literal containing the version of cairo available at compile-time, in the form of "X.Y.Z". This macro encodes the given cairo version into an integer. The numbers returned by %CAIRO_VERSION and cairo_version() are encoded using this macro. Two encoded version numbers can be compared as integers. The encoding ensures that later versions compare greater than earlier versions. @major: the major component of the version number @minor: the minor component of the version number @micro: the micro component of the version number @Returns: the encoded version. This macro encodes the given cairo version into an string. The numbers returned by %CAIRO_VERSION_STRING and cairo_version_string() are encoded using this macro. The parameters to this macro must expand to numerical literals. @major: the major component of the version number @minor: the minor component of the version number @micro: the micro component of the version number @Returns: a string literal containing the version. @Since: 1.8 @Returns: @Returns: