cairo-version-info: Version Information
In RGtk2: R Bindings for Gtk 2.8.0 and Above

Description Methods and Functions Detailed Description Compatibility Examining the version Author(s) References

Compile-time and run-time version checks.

cairoVersion()
cairoVersionString()

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 function cairoVersionEncode() to perform the encoding.

Compile-time
--------
R users should not be concerned with compile-time version checking.

Run-time
--------
cairoVersionString()	Human-readable, use compareVersion() for comparison
cairoVersion()		Encoded, not very useful in R

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:

# R users should not be concerned with compile-time checking, but at runtime:

if (compareVersion(cairoVersionString(), "1.0.0") == 1)
  cat("Running with suitable cairo version:", cairoVersionString(), "\n")