Re: [gentoo-dev] ebuild USE priority

[Erik Grinaker]

On Wed, 2002-05-15 at 06:55, Matthew Kennedy wrote:

> On Tue, 2002-05-14 at 17:23, Erik Grinaker wrote:
> > The ebuild is for the Unix Amiga Emulator, or uae for short. uae allows
> > you to select which backend to compile against during ./configure, and
> > you can choose *either* x, svgalib, ncurses or sdl.
>
> When creating the xemacs-gamma ebuild I encountered the same dillema.
> When you say "*either*", I assume you mean that X, svga, ncurse and sdl
> are optional, but mutually exclusive.

Yep, that's right.


> > If a user has, say, both X and svga in his USE variable, how do I
> > determine whether to use X or svgalib for backend?
>
> XEmacs gamma supports gtk OR motif OR lucid interfaces (each of which
> can be considered a use flag) in mutual exclusion. Of course, I don't
> want to dictate one of those three to the user, since my preference may
> not be theirs.
>
> I thought of a priority scheme, but couldn't see clearly how that would
> be done. How did you do it, BTW?

Well, I haven't completed the ebuild yet, but I decided to go for my own
priorities ;

    use ncurses &&  backend="--with-asciiart"
    use svga &&     backend="--with-svgalib"
    use sdl &&      backend="--with-sdl --with-sdl-sound --with-sdl-gfx"
    use X &&        backend="--with-x"

These are set in reverse so that the last one that matches will be
active. But I'm really not satisfied with this, because if a user would
like to have, as you say later in your mail, an svga emulator while
having both x and svga in his USE then his only option would be to
manually change USE before emerging.


> What I ended up doing was checking for an env. var. named USE_PREF which
> is localized to xemacs-gamma. It allows the user to merge xemacs-gamma
> like this:
>
>    USE_PREF=gtk app-editors/xemacs-gamma

This seems to be quite sensible, even though it creates it's share of
troubles when checking DEPENDs. Does any of the Gentoo developers have
any thoughts on this?


-- 

Erik Grinaker
Freelance UNIX/Linux systems consultant

"Perfection is acheived not when there is nothing more to add, but
rather when there is nothing more to take away"
- Antoine de Saint-Exupéry