[Epiphany] Tabs options

[Marco Pesenti Gritti <marco gnome org>]

I think we need to fix the preferences for tabs in 1.2. Currently we
have one pref "Open in tabs by default", that doesnt do what it is say
(external links and popups are opened in windows) and that does more of
what it says (tab bar is ever visible when set.

Trying to summarize, there are 4 boolean preferences:

Ever show the tab bar

I consider it a work around pref to avoid page movement when opening
second tab -> it should only be in gconf, no ui for it.
Dave suggested that tab bar on the bottom could solve the actual problem.

Open popups in tab

This is more controversial. It can be considered a work around for
lacking popups blocking or a way to do popup blocking that better feel
some people needs. I'd tend to say gconf only but I'm not super strong
feeling

Open in tab on middle click

This is a mess. We could decide to turn on middle click in tabs by
default but if we decide we need a pref, a better description is
necessary, to limit it only to the cases it's actually used. Currently
both external links and popups doesnt follow it, so the label is wrong.

External links in tabs

There are people that use only one window with tabs, like true MDI.
I dont think supporting MDI make much sense in epiphany... so this would
be just a make hackers happy thing. It could be grouped with popups
(resulting in a MDI switch) or we could just keep current command line
option.

Costs/benefits evaluation of the 2-3 hidden prefs. 
1 The MDI switch which would now really open everything in tabs (also
external links and popups). This should be definately an hidden pref
because it implements something that HIG dissugest (gedit uuughh ;),
and because it introduce potentially crack results (links opened in a
"random" window). Costs could be not trivial here (popups in tabs are
a pain to implement and could cause bugs), but benefits could be good
(a lot of people are likely to use it).
2 The autohide thing. If we can solve that with tabs position great,
but I think it's something that need to be discussed with usability
guys, we would introduce an inconsistency with other apps. Otherwise
here I think both costs and benefits are lower. The implementation is
very simple but I doubt many people would bother changing the pref ...

Finally the only interesting thing from an interface design pov here is
the middle click->open in tab by default thing. I think it make sense because
if we support tabs as a threaded navigation tool, we should definately use
it by default when opening links in another "page".
Also we would have a complete "tabs as threaded navigation tool" implementation,
without need of tweaking settings.
This obviously imply tabs are a good tool for threaded navigation.
(but if they arent, why we support them ?)

/me is sort of worried of the flames we will get if we remove the
last tab pref :)

I'd really like to hear opinions about these before we start to make changes.
I want to start making changes only if when we see the big picture.

Marco