I used to ship toolbar icons with the plugin to be sure they are correct semantically. For instance, the "+" icon is used to expand the tree and the semantics of the corresponding icon in GTK is "add" - some crazy theme could for instance use word "ADD" in the icon and then the icon wouldn't correspond to the "expand" meaning.
However, I've just been playing with many icon themes on OS X and they display these basic icon in more or less the same way so using stock icons seems to be relatively safe. This also solves the problem of the shipped icon being displayed in a different way than the rest of the system icons and in addition, if HiDPI icons are available, they can be used on a highres monitor. You can view, comment on, or merge this pull request online at:
https://github.com/geany/geany-plugins/pull/625
-- Commit Summary --
* projectorganizer: Use stock icons instead of the ones provided by the plugin
-- File Changes --
M build/projectorganizer.m4 (1) M projectorganizer/Makefile.am (2) D projectorganizer/icons/Makefile.am (23) D projectorganizer/icons/prjorg-add-external.png (0) D projectorganizer/icons/prjorg-collapse.png (0) D projectorganizer/icons/prjorg-expand.png (0) D projectorganizer/icons/prjorg-file.png (0) D projectorganizer/icons/prjorg-follow.png (0) D projectorganizer/icons/prjorg-header.png (0) D projectorganizer/icons/prjorg-refresh.png (0) D projectorganizer/icons/prjorg-source.png (0) M projectorganizer/src/prjorg-sidebar.c (59)
-- Patch Links --
https://github.com/geany/geany-plugins/pull/625.patch https://github.com/geany/geany-plugins/pull/625.diff