Defining custom "use-expand" use flags in an overlay?

[StifflerStealth]

I am writing some ebuilds that I want to use the "use-expand" feature for and I want to make my own use-expand that is not in Gentoo. How do I go about setting this up? I know the current use-expands are defined in profiles/base/make.defaults in the main Gentoo tree, so how do I define my own?

Thanks
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[Sadako]

I'm not completely sure if this is what you want, but I've done something similar with custom xorg-server ebuilds.

I made a lot of the x11 extensions optional via use flags, ie I had defined IUSE_X11_EXTENSIONS="glx", and included it in IUSE (via IUSE="${IUSE_X11_EXTENSIONS}"), then in the ebuild everything glx related would depend upon the x11_extensions_glx USE flag.

Then in make.conf I added USE_EXPAND="${USE_EXPAND} X11_EXTENSIONS", and all the x11_extensions_* USE flags worked just like LINGUAS or VIDEO_CARDS, and to enable the ones you want you'd set something like X11_EXTENSIONS="composite xv" in make.conf.

Of course, I could be misunderstanding you completely...
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[StifflerStealth]

That's what I want, something that acts like LINGUS and VIDEO_CARDS use-expands. Though, my wondering is if there is a way to define it in the overlay instead of doing it in make.conf. Maybe something in the profiles directory?

So, in my ebuild, I use IUSE_MY_VARIABLE="useflag" and useflag expands to my_variable_useflag? I looked at xorg-server ebuild and they do:
IUSE_INPUT_DEVICES="
input_devices_acecad
..."

Do I need to follow that, or did the ebuild author choose to do things the long way?

Thanks for replying.
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Nothing to read in this sig. Move along.

[Sadako]