The usual way to implement a container actor is to override the
allocate() virtual function, chain up, and then allocate the actor's
children.
Clutter now has the ability to delegate layout management to
ClutterLayoutManager directly; in the allocation, this is done by
checking whether the actor has children, and then call
clutter_layout_manager_allocate() from within the default implementation
of the ClutterActor::allocate() vfunc. The same vfunc that everyone, has
been chaining up to.
Whoopsie.
Well, we can check if there's a layout manager, and if it's NULL, we
bail out. Except that there's a default layout manager, and it's the
fixed layout manager, so that classes like Group and Stage work by
default.
Double whoopsie.
The fix for this scenario is a bit nasty; we have to check if the actor
class has overridden the allocate() vfunc or not, before actually
looking at the layout manager. This means that classes that override the
allocate() vfunc are expected to do everything that ClutterActor's
default implementation does - which I think it's a fair requirement to
have.
For newly written code, though, it would probably be best if we just
provided a function that does the right thing by default, and that
you're supposed to be calling from within the allocate() vfunc
implementation, if you ever chose to override it. This new function,
clutter_actor_set_allocation(), should come with a warning the size of
Texas, to avoid people thinking it's a way to override the whole "call
allocate() on each child" mechanism. Plus, it should check if we're
inside an allocation sequence, and bail out if not.
If we want to set a default layout manager, we need to do so inside
init(), as it's not guaranteed that people subclassing Actor and
overriding ::constructed will actually chain up as they should.
The default pick() behaviour does not take into consideration the
children of a ClutterActor because the existing containter actors
usually override pick(), chain up, and then paint their children.
With ClutterActor now a concrete class, though, we need a way to pick
its children without requiring a sub-class; we could simply iterate over
the children inside the default pick() implementation, but this would
lead to double painting, which is not acceptable.
A moderately gross hack is to check if the Actor instance did override
the pick() implementation, and if it is not the case, paint the children
in pick mode.
The hide_all() method is pretty much pointless, as hiding an actor will
automatically prevent its children from being painted. The show_all()
method would only be marginally useful, if actors weren't set to be
visible by default when added to another actor - which was the case when
we introduced show_all() and hide_all().
* Abstracts the buffer for text in ClutterText
* Allows implementation of undo/redo.
* Allows use of non-pageable memory for text
in the case of sensitive passwords.
* Implement a test with two ClutterText using the same
buffer.
https://bugzilla.gnome.org/show_bug.cgi?id=652653
When dereferencing GArray.data to a C structure you need a double cast
from guint8* to void*, and then from void* to the actual type. This
avoids compiler warnings, especially when using clang on OSX.
The concept of "internal child" only meant anything when we had a
separate API for containers and actors. Now that we plugged that
particular hole, we can drop all the hacks we used to have in place
to work around its design limitations.
It can be convenient to be able to set, or get, all the components of an
actor's margin at the same time; since we already have a boxed type for
storing a margin, an accessors pair based on it is not a complicated
addition to the API.
Inside the set_child_[above|below]_sibling() and set_child_at_index() we
should be using the internal API for mutating the children list, instead
of the delegate functions. This ensures that we go through a single,
well-defined code path for all operations on the list of children of
an actor.
We have a replacement in ClutterActor, now.
The old ClutterContainer API needs to be deprecated, and the raise() and
lower() virtual functions need a default implementation, so we can check
for implementations overriding them, by using the diagnostic mode like
we do for add(), remove(), and foreach().
The sort_depth_order() virtual function just doesn't do anything, as it
should have been made ages ago.
The Actor wrappers for the Container methods also need to be deprecated.
ClutterActor provides four methods for changing the paint sequence order
of its children:
raise_top()
raise()
lower()
lower_bottom()
The first and last one being just wrappers around raise() and lower(),
respectively. These methods have various issues: they omit the parent,
preferring to retrieve it from the actor passed as the first argument;
this does not match the new style of API introduced to operate on the
list of children of an actor.
Additionally, the raise() and lower() methods of ClutterActor call into
the Container interface, and are not really aptly named (raise() in
particular collides with the completely unrelated 'raise' keyword in
Python, and usually needs to be wrapped in order to be used at all).
Furthermore, we need public methods that Container can call from its
default implementation, as well as methods to port current Container
implementations.
Finally, since we have insert_child_at_index(), we should also have an
equivalent set_child_at_index() as well.
The internal versions of add_child() and remove_child() currently use
boolean arguments to control things like the ChildMeta instances and
the emissions of signals; using more than one boolean argument is an
indication that you need flags to avoid readability issues, as well as
providing a way to add new behaviours without a combinatorial explosion
of arguments, later on.
I don't feel comfortable with this feature, and its implementation
still has too many rough edges. We can safely punt it for now, and
introduce it at a later point, as it doesn't block existing features
or API.
This virtual function will let layout managers with legacy expansion
flags be able to influence the lazy computation of the expansion flags
on ClutterActor.
We need to paint the background color in the default class handler for
two reasons: it's logically appropriate, and we don't want actor
subclasses overriding the ::paint class handler to change behaviour only
because somebody decided to set the background color.
The old add(), remove(), and foreach() virtual functions are deprecated;
ClutterContainer should warn if the public API detects that the vfuncs
have been overridden.
Strictly speaking, it's still legal to override those vfuncs: you can
chain up to the default vtable, or you could just provide an equivalent
implementation. The goal is to avoid having to override the Container
interface, until we can safely deprecate it and remove it in Clutter
2.0.
Instead of making ClutterActor implement the basic add/remove/foreach
virtual functions of ClutterContainer, we can simply do that from
within the ClutterContainer implementation.
The get_children(), foreach(), and foreach_with_internals() methods and
virtual functions are superceded by the Actor API, and should not be
used in newly written code.
Given the size and scope of the changes in ClutterActor, we ought to
rewrite the overall description of what an actor is, what it does, and
how are you supposed to use it and subclass it.
This will make things interesting.
We have better replacements in ClutterActor, that do The Right Thing™
instead of deferring control and requiring reimplementation in every
single container actor.
The correct sequence of actions should be remove(old) → insert(new), not
insert(new) → remove(old). We can implement a simple delegate insertion
functions to insert the new child between the previous and next siblings
of the old child.
While we're at it, let's also add a unit test for replace_child().
Providing a default get_paint_volume() that takes into account the
children of an actor was a goal of the whole First Apocalypse; if we
make all the containers rely on it, and yet we return a FALSE value
(meaning: we don't have a valid paint volume) even when we do have it,
then we are going to break the whole machinery, though.
Cally is doing a bunch of list traversals through the list returned by
ClutterContainer.get_children(); this means a traversal already, plus
a bunch of allocations. We can do better than that, now that we have
a proper graph iteration API inside ClutterActor.
The insert_child_at_index, insert_below and insert_above messed up the
first and last child pointers in various cases. This commit fixes all
the instances of first and last child pointers being stale or set to
NULL.
Instead of getting the list of children to iterate over it, let's use
the newly added child iteration API; this should save us a bunch of
allocations, as well as indirections.
Ported: ClutterBinLayout and ClutterBoxLayout.
Instead of requiring every consumer of the ClutterActor API that wishes
to iterate over the children of an actor to use the get_children()
method, we should provide an iteration API directly inside ClutterActor
itself.
Instead of storing the list of children, let's turn Actor inside a
proper node of a tree.
This change adds the following members to the Actor private data
structure:
first_child
last_child
prev_sibling
next_sibling
and removes the "children" GList from it; iteration is performed through
the direct pointers to the siblings and children.
This change makes removal, insertion before a sibling, and insertion
after a sibling constant time operations, but it still retains the
feature of ClutterActor.add_child() to build the list of children while
taking into account the depth set on the newly added child, to allow the
default painter's algorithm we employ inside the paint() implementation
to at least try and cope with the :depth property (albeit in a fairly
naïve way). Changes in the :depth property will not change the paint
sequence any more: this functionality will be restored later.
ClutterTransformInfo is a (private) ancillary data structure that
contains all the decomposed transformation data, i.e. rotation angles
and centers, scale factors and centers, and anchor point. This data
structure is stored in the GData of the actor instance instead of the
actor's private data. This change gives us:
• a smaller, cleaner private data structure;
• no size penalty for untransformed actors;
• static constant storage for the defaults, shared across all
instances;
• cache locality for all the decomposed transformation data,
given that the structure size is smaller.
At the end of the day, the only authoritative piece of information for
actor transformation is the CoglMatrix that we initialize in
apply_transform() from all the decomposed parameters, and that can stay
inside the private data structure of ClutterActor.
There are only two kinds of actors that allow underallocations,
according to the API contract:
• ClutterStage, as it is a viewport and it doesn't have an implicit
minimum size;
• Actors using the CLUTTER_ACTOR_NO_LAYOUT escape hatch, which allows
them to bail out from our layout management policies.
The warning about underallocations should take these two exceptions
under consideration.
The Group functionality is now provided by ClutterActor.
Sadly, we need to keep the ClutterGroup structure definition in the
non-deprecated header because ClutterStage inherits from Group - an API
wart that was never fixed during the 0.x cycles, and that we'll have to
keep around until we can break API.
ClutterBox functionality has been implemented by ClutterActor, and
proxied by the Box subclass; with the removal of the abstract bit on
ClutterActor, we can safely deprecated ClutterBox.
ClutterActor now has all the API and capabilities for being a concrete
class:
- layout management, through delegation
- container implementation and API
- background color
This means that a simple scene can be built straight out of actors
without using subclasses except for the Stage.
This is the first step towards the deprecation of most of the Actor
subclasses provided by Clutter.
ClutterActor can do better by default than just giving up immediately.
An actor can check for the clip region, and for its children's paint
volume, for instance.
Just these two should give us a better default implementation for newly
written code.
The minimum preferred size of a Flow layout manager is the size of a
column or a row, as the whole point of the layout policy enforced by
the Flow layout manager is to reflow when needed.
ClutterBox's color and color-set properties can be implemented as
proxies for the ClutterActor's newly added background-color and
background-color-set properties, respectively.
This also allows us to get rid of the paint() implementation inside
ClutterBox altogether.
Each actor should have a background color property, disabled by default.
This property allows us to cover 99% of the use cases for
ClutterRectangle, and brings us one step closer to being able to
instantiate ClutterActor directly.
And make sure that overriding Container and calling
clutter_actor_add_child() will result in the same sequence of operations
as the current set_parent()+queue_relayout()+signal_emit pattern.
Existing containers can continue using:
clutter_actor_set_parent (child, CLUTTER_ACTOR (container));
clutter_actor_queue_relayout (CLUTTER_ACTOR (container));
g_signal_emit_by_name (container, "actor-added", child);
and newly written containers overriding Container.add() can simply call:
clutter_actor_add_child (CLUTTER_ACTOR (container), child);
instead.
We need to queue a relayout when removing a visible child from a visible
parent.
We also need to insert the child at the right position (depending on the
depth) so that newly added actors will be painted on top.
Remove four more floats from ClutterActorPrivate.
The fixed minimum and natural sizes should be stored inside the
ClutterLayoutInfo structure, along with the fixed position.
Add a failsafe against a NULL parent, to avoid a segfault when calling
clutter_actor_allocate() on the Stage.
We also need to deal with floating point values: straight comparison is
not going to cut it.
ClutterActor has various properties controlling the allocation:
- x-align, y-align
- margin-top, margin-bottom, margin-left, margin-right
These properties should adjust the ClutterActorBox passed from the
parent actor to its children when calling clutter_actor_allocate(),
so that the child can just allocate its children at the right origin
with the right available size.
The actor class should be able to hold the margin offsets like it does
for expand and alignment flags.
Instead of filling the private data structure with data, we should be
able to use an ancillary data structure, given that all this data is
optional and might never be set in the first place.
In case no layout manager was set during construction, we fall back to a
FixedLayout. The FixedLayout has the property of making the fixed
positioning and sizing API, as well as the various Constraints, work
out of the box.
Now that ClutterActor implements the Container contract we can actually
defer the size negotiation to a ClutterLayoutManager directly from the
default implementation of the Actor's virtual functions.
We can provide most of the ClutterContainer implementation directly
within ClutterActor — basically removing the need of having the
Container interface in the first place. For backward compatibility
reasons we can keep the interface, but let Actor implement it directly.
Let's try and move away from the reverse implicit scene graph build API,
which we mutuated from GTK+, towards a more traditional node/child API.
The set_parent()/unparent() API is confusing, unless you know the
history; having a add_child()/remove_child() methods pair makes it more
explicit.
We can easily implement the old set_parent()/unparent() pair in terms of
the newly add_child()/remove_child() one.
Enclose the check inside a #ifdef CLUTTER_ENABLE_DEBUG ... #endif, so
that we can compile it out; also, use g_string_append() instead of the
g_string_append_printf() function, given that we're just concatenating
strings.
The ::redraw virtual function was a throwback from olden times, and has
been thoroughly replaced by the equivalent vfunc on the StageWindow
interface. We can safely remove it, now, and simplify the flow of the
redraw code inside ClutterStage.
