Crusty Blaa

If you're wondering how to move your GNOME jhbuild from CVS now that the SVN migration has happened ... here's what I had to do.

• Checkout jhbuild from SVN:

    $> mkdir -p /gnome/head/svn && cd /gnome/head/svn
    $> svn co svn+ssh://markmc@svn.gnome.org/svn/jhbuild/trunk jhbuild
    $> make install
  

• Update ~/.jhbuildrc so that e.g.

    repos['svn.gnome.org'] = 'svn+ssh://markmc@svn.gnome.org/svn/'
    checkoutdir = '/gnome/head/svn'
  

• Copy /gnome/head/cvs/pkgs to /gnome/head/svn/pkgs so that you won't have to download as many new tarballs

• Run jhbuild build

Note, this is with the gnome-2.18 moduleset. Things are still a little in flux right now.

I've posted description to the Fedora wiki about how we're implementing the cached client part of Stateless Linux in FC6.

Pile onto the stateless-list if you want to yak about it.

What I find most interesting about Mughsot is the team's total and no-bullshit commitment to making new and interesting software which doesn't suck.

I love the way they say their design process "isn't a checklist of activites you must do - it's an idea list, suggestions for how to work smarter". I love the way they prototyped a photos feature using flickr but were willing to drop it again after trying it on real people. I love the way they lock themselves in a room, leaving their laptops behind, and give themselves the time to hash out ideas properly.

I hope Mugshot itself is a success. But, more than that, I hope they help change the way the rest of us make software.

Aren't discussions via blogs fun? :)

Federico: two points:

1. Using the new GObject instance private data API, rather than the private data scheme that GNOME hackers have always used, is a small optimization in itself - the private data is allocated in the same chunk as the object itself.

   As with all optimizations, you weigh up the benefit against the code obfuscation. In this case, I don't think the GObject scheme makes the code more difficult to understand ... especially since it's likely to become as much of a second-nature idiom as the old scheme. It's also one less opportunity to leak memory.

2. Using the GObject scheme, instance private data could have been added without the runtime hit you were seeing ... even where the object structure couldn't be extended without breaking ABI.

   To do so, you'd just go back to something similar to Owen's initial suggestion for how the API should be used - in a static variable, you'd store the offset between the address of the object structure and the private data and use that offset for efficient access to the data. add_private() originally returned this offset, but it no longer does, so you'd need to calculate the offset in instance_init() - but it is guaranteed to be constant.

   Granted, that's a nasty hack which would genuinely obfuscate the code ... but at least it would actually be possible to add private data, whereas it wouldn't be possible with the old scheme.

   Update: Tim points out that the offset to the private data isn't constant across all instances - the offset will be larger for subtypes since the private data is allocated after all object data.

Federico: the combination of a "*priv" field and GObject private data is the best way to go:

struct _PangoFcFont
{
   ...
   gpointer priv;
   ...
};

#define PANGO_FC_FONT_GET_PRIVATE(obj) ((PangoFcFontPrivate *) ((PangoFcFont *) obj)->priv)

static void
pango_fc_font_class_init (PangoFcFontClass *class)
{
  ...
  g_type_class_add_private (object_class, sizeof (PangoFcFontPrivate));
}

static void
pango_fc_font_init (PangoFcFont *fcfont)
{
  fcfont->priv = G_TYPE_INSTANCE_GET_PRIVATE (fcfont, PANGO_TYPE_FC_FONT, PangoFcFontPrivate)
}

Indeed, that's why g_type_get_private() was added. You get the best of both worlds - the convenience of a priv pointer with the fact that the private data is allocated in the same chunk as the object itself, without the inefficiency of calling get_private() a lot or the extra static variable in Owen's original proposal.