[launcher] Better integration with OS specific application data directories

[laeubi]

Currently we only support limited placeholders in the equinox native launcher

@launcher.dir
    Directs Eclipse to compute a location value relative to the directory containing the Eclipse launcher binary. @launcher.dir can be followed by additional path segments. In all cases, the string "@location.dir" is simply replaced with the parent directory of the path pointed to by the Java "eclipse.launcher" System property. For example, setting
        osgi.install.area=@launcher.dir/../../../pool
    results in a value of
        file:/home/bob/eclipse-product/linux/gtk/x86_64/../../../pool
    if the "eclipse.launcher" property is set to "/home/bob/eclipse-product/linux/gtk/x86_64/eclipse".
@user.home
    Directs Eclipse to compute a location value relative to the user's home directory. @user.home can be followed by additional path segments. In all cases, the string "@user.home" is simply replaced with the value of the Java "user.home" System property. For example, setting
        osgi.instance.area=@user.home/myWorkspace
    results in a value of
        file:/users/bob/myWorkspace
@user.dir
    Directs Eclipse to compute a location value relative to the current working directory. @user.dir can be followed by additional path segments. In all cases, the string "@user.dir" is simply replaced with the value of the Java "user.dir" System property. For example, setting
        osgi.instance.area=@user.dir/myWorkspace
    results in a value of
        file:/usr/share/eclipse/myWorkspace

but for example in windows/linux there are user specific places where one should place things look here:

• https://learn.microsoft.com/en-us/dotnet/api/system.environment.specialfolder?view=netframework-4.8
• https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard

to make Eclipse Applications integrate better in these we should add more placeholders that map to OS specific things, e.g. we might want:

• @user.data should map to ApplicationData on windows and $HOME on Linux (difference to @user.home what is feed by javasystemproperty) and replacing the first path segment with a . so for example @user.data/myApp should resolve to '%APPDATA%\myApp on Windows and $HOME/.myApp on Linux
• @user.data.shared should map on CommonApplicationData on windows and /srv on linux
• @user.documents should map on Personal on windows and $HOME on linux
• ... maybe more ideas that are usual places for application data ...

Of course the same needs to be investigated for Mac I have not found yet where these equivalent to linux or if there are other "standards" in MacOS

[ejjcase]

I was about to report the same thing, but suggest doing the substitution in EquinoxLocations instead of, or as well as, in the binary launcher.

The reason is that I'm using Bnd to build my application. With this method, most of the system properties are read from a properties file, and thus don't pass through the binary launcher.

I particularly want to set osgi.instance.area to a location that uses APPDATA on Windows.

[basilevs]

Note, that XDG (linked to at the bottom of Filesystem_Hierarchy_Standard) provides more fine-grained standard for Linux user directories. It would be rude to dump everything in $HOME. It would be nice to find an equivalent for Wayland environment though, because XDG focuses on Xorg.

A list of standard directories for MacOS

[akurtakov]

Historically the X in XDG was related to X11 but nowadays XDG is display protocol agnostic and there is no need to look for other things for Wayland.

[laeubi]

There is of course always room to improve... this was a more minimalist approach to get this better integrated on windows but of course it was not meant to forbids other standards.