Hi,
I'm trying to wrap the animation classes in Cluttermm.
Clutter::Animation is the basic animation class. It's got a restricted
interface- for instance it only animates one object, and the start and
finish times are the only two points where an actor's location can be
defined.
In the C code it's used for simple animations, but accessed through
clutter_actor_animate, and there's a bit of initialisation that happens
in there that doesn't happen in the class constructor. In particular,
the Timeline is initialised beside the Animation, not inside it.
What that seems to mean is that wrapping the Animation class has
unexpected issues. The code below has a problem:
/*a bit of initialisation above this*/
Glib::RefPtr<Clutter::Animation> animation =
Clutter::Animation::create();
animation->set_object(rect);
animation->set_duration(5000); /*HERE*/
//only way to get the animation's timeline:
const Glib::RefPtr<Clutter::Alpha> my_alpha =
animation->get_alpha();
const Glib::RefPtr<Clutter::Timeline> tl =my_alpha->get_timeline();
tl->set_duration(3000); /*this should be sufficient */
//bind a value:
animation->bind("x", 150);
//bind with a start and a finish value:
animation->bind_interval("opacity", 0, 255);
stage->show();
//start the timeline:
tl->start();
// Start the main loop:
Clutter::main();
If I compile the above, it works (I've had to wrap the bind() methods
first- that's this bug report
<https://bugzilla.gnome.org/show_bug.cgi?id=660307> ). If I comment out
the animation->set_duration(), it segfaults; I think it's probably
because the Timeline isn't properly initialised in the Animation class
init().
So, questions.
1) is it worth fixing this for a basic interface that's unlikely to get
much use?
2) The issue for Cluttermm is that clutter_actor_animate hasn't been
wrapped, so is it a better option to wrap the clutter_actor_animate
function, and hide the Animation class from the user (as currently
happens in C)?
3) I think it's due to the way the C code uses ClutterAnimation, not a
problem with the C++ wrapper. Given the code above, does that make sense?
4) A general wrapping question. All the functions I'm having to wrap
manually can take any value, and in C they convert it to a GValue. For
animations there's no point taking non-numeric values ( there's no
intrinsic way to increment a string value, for instance) so if the value
is non-numeric it shouldn't be accepted as input. Is it reasonable to
screen for that in the function wrapper?
Ian.
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