Sunday, November 12, 2017

Surreptitious Submodule Switch

During the last couple of days, we've transitioned all the third party libraries used by wxWidgets, such as libpng, libjpeg and so on, to use Git submodules instead of just subdirectories in the main repository. If you don't use Git to get the latest and greatestfor the appropriate definition of "great" wxWidgets, you don't need need to read further as it shouldn't affect you in any way except for resulting in faster and more frequent updates to these libraries (but still consider starting to use sources from Git to help us with testing!).

If you do use Git, you will notice that your next update, i.e. git pull or git fetch && git merge --ff-only origin/master, will delete all files in src/{expat, jpeg, png, tiff, zlib} directories. Do not be alarmed by this but do run

git submodule update --init
to initialize and get the latest contents of all the submodules. This will, unfortunately, take quite some time, and if you use a not too ancient version of Git (2.8 or later), you should be able to speed the process up significantly by doing
git fetch --recurse-submodules -j2
instead, where "2" could be replaced by any number up to 5 (higher would be useless with only 5 submodules).

During subsequent updates, if you notice any change to one of the submodules, you need to only rerun git submodule update (without the --init option) and it will be much faster. Other than that, your use of wxWidgets Git repository shouldn't have to change in any way, the only difference is now most of Git commands won't recurse into submodules, at least by default, so git grep, for example, won't find any matches in the subdirectories mentioned above by default. However mostly the new behaviour is more useful, and you can use the same --recurse-submodules option with a few Git commands to change it if really needed.

Of course, if you do find any problems due to the switch to submodules or third party libraries upgrades that have taken place together with it (we now use the latest versions of all of them, notably jumping from libjpeg 6b released in 1998 to 9b, released in 2016), please let us know on the mailing lists, as usual.

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