Now that Clutter 0.6 is out, I found the time to finish the planned sections for the Clutter tutorial that I mentioned in December, for Openismus. Here is the html version and a PDF, though of course the PDF doesn’t have the nice links into the API reference documentation and the links to the actual files of the examples.
The guys at OpenedHand haven’t had time to review this yet, so be aware that there could be significant errors. But I think it’s mostly accurate, useful, and unique, though the appendices and full example are obviously lacking. I’ll try to keep it up to date and correct as I get feedback.
Having done all this investigation into Clutter, I have formed some opinions:
- Clutter is a nice way to move semi-3D things around on the screen to create “innovative” user interfaces. Its abstractions for actors and behaviours really give you something to work with compared to using OpenGL directly. But it’s still hard to create natural-feeling responsive applications and I don’t know exactly what’s lacking. It feels like there is a disconnect between the act of coding and the very dynamic UIs that the code creates. I sometimes feel I’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.
- Clutter is now a very basic API. You will need to implement a lot of simple functionality to create applications that act as today’s users expect. The Tidy “reference-implementation” example toolkit thing is not a shared library – it’s meant as an inspiration for you to do all this yourself, and it is itself not very complete. I don’t think that is a wise strategy, though rampant bad reimplementation is the standard in today’s mobile/embedded development projects.
- Neither you or Clutter should want to reimplement the huge amount of UI logic that is, for instance, in GTK+. Without reusing all that work, Clutter applications will generally have inconsistent or inadequate text editing, scrolling, focus, keyboard accessibility, right-to-left language support, etc. Applications will share little common API so it won’t be easy to throw new developers at your project. Somehow we need a way to use some GTK+ widgets in Clutter without them looking and feeling like they are visitors from an extra dimension.
These problems could probably be solved by lots of hard work by smart people. I don’t know what the near-future strategy for Clutter is, so I don’t know if the current state is intentional or if anything particular is planned. It’s certainly getting better all the time.