[HIG] How much intendation should be used for grouped widgets?

[Christian Neumair <chris gnome-de org>]

Our current HIGifying situation is more than unsatisfying when it comes
to the category intendation. Currently three different values are used:
12 px, 18 px as well as 4 spaces ("    ").
While the HIG states that you ought to "(i)ndent group members 12 pixels
to denote hierarchy and association." [1], another image on the same
page [2] obviously uses 18 px for that. In my opinion this shows that
the HIG authors themselves prefer 18 px over 12 px.
In my AbiWord HIGifying efforts I used 18 px for that intendation and I
must say that it looks way better than 12 px. Third candidate it the
"    " intendation, but I don't think it's a good idea to make the
indenation dependant on the currently used font width.

regs,
 Chris

[1]
http://developer.gnome.org/projects/gup/hig/1.0/layout.html#window-layout-spacing

[2]
http://developer.gnome.org/projects/gup/hig/1.0/images/layout_callouts.png