Murray, just a short reply to your points:
I sometimes feel Iâ€™d like to just put actors on a rail, twist that rail about, connect some actors together with struts or springs, start them moving, let the user push and pull them around within constraints, and trigger extra behaviour when they reach certain positions, or reach each other.
What you want is a physics engine hooked up into Clutter; it’s possible, Pippin has been doing some preliminary work on it, and it would solve the more “physical” interaction model. But it’s not always what you want your UI to look like and it’s not always a good model to employ, especially if you cannot interact physically with the UI – like shaking it, rotating it, use multi-touch surfaces.
Clutter is now a very basic API.
You make it sound like it’s a bad thing. Well, it’s not: it’s exactly what we want it to be like. No constraints on the UI structure or behaviour — those belong to toolkits developed on top of Clutter. Like Tidy, which is a shared library (it even installs a pkg-config file), but it will not be released as a tarball because we’d like to keep it as an experimental ground, read: breaking stuff, to see how and what should Clutter provide to implement an accelerated and animated toolkit. Also, as you note, in embedded environments you’ll want to style and create your entire stack: instead of raping and twisting GTK+ themeing until you don’t know that you’re using GTK+ anymore — and losing a lot of time in the process — you can use a standard low level API and develop your toolkit on top of it. It’s not optimal, but I think it’s a step in the right direction to make the GNOME mobile stack a lot more useful and flexible.
Neither you or Clutter should want to reimplement the huge amount of UI logic that is, for instance, in GTK+
That is why you can embed Clutter inside a GTK+ application, and hopefully you’ll soon be able to embed GTK+ widgets inside Clutter.
In short: Clutter was never meant or designed or developed to be a complete replacement for GTK+ on the desktop. On the desktop is an API for allowing hardware accelerated UIs embedded into current applications (photo slide shows for Eog; music library browsing for Rhythmbox; login user browser for GDM; and these are just the first items that come to mind). In the mobile environment arena, Clutter is meant to be used as a cornerstone – along with GLib, GStreamer and the rest of the GNOME mobile stack – for developing a new kind of UI, where the desktop guidelines and style don’t apply.