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[docs] Update the "Subclassing Actor" chapter

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The chapter on how to subclass ClutterActor inside the API reference for
Clutter is still using ClutterUnit and referencing to concepts that have
been changed since the document was written.
This commit is contained in:
Emmanuele Bassi 2009-09-27 11:38:01 +01:00
parent ab76d64df0
commit 6ddffac935
1 changed files with 108 additions and 63 deletions
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171
doc/reference/clutter/subclassing-ClutterActor.xml
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@ -5,7 +5,7 @@
<surname>Bassi</surname>
<affiliation>
<address>
<email>ebassi@openedhand.com</email>
<email>ebassi@linux.intel.com</email>
</address>
</affiliation>
</author>
@ -40,13 +40,11 @@ G_DEFINE_TYPE (FooActor, foo_actor, CLUTTER_TYPE_ACTOR);
static void
foo_actor_class_init (FooActorClass *klass)
{
}
static void
foo_actor_init (FooActor *actor)
{
}
</programlisting>
</informalexample>
@ -84,10 +82,13 @@ foo_actor_init (FooActor *actor)
specific resources associated with being added to the #ClutterStage,
and whether their children should be painted or not. A
#ClutterContainer implementation should not care about overriding
the ClutterActor::realize(), ClutterActor::unrealize(),
ClutterActor::map() and ClutterActor::unmap() virtual functions, but
the <classname>ClutterActor</classname>::realize(),
<classname>ClutterActor</classname>::unrealize(),
<classname>ClutterActor</classname>::map() and
<classname>ClutterActor</classname>::unmap() virtual functions, but
composite actors with private children MUST implement at least
ClutterActor::map() and ClutterActor::unmap().</para></listitem>
<classname>ClutterActor</classname>::map() and
<classname>ClutterActor</classname>::unmap().</para></listitem>
</varlistentry>
</variablelist>
@ -130,8 +131,8 @@ foo_actor_init (FooActor *actor)
of space an actor would occupy if nothing would constrain it.</para>
<note><para>The natural size must always be greater than, or equal
to the minimum size. #ClutterActor will warn in case this assumption
is not respected by an implementation.</para></note>
to the minimum size. #ClutterActor will just ignore a natural size
lesser than a minimum size.</para></note>
<para>The height request may be computed for a specific width, which
is passed to the implementation, thus allowing height-for-width
@ -144,7 +145,10 @@ foo_actor_init (FooActor *actor)
<note><para>The clutter_actor_get_preferred_size() function will
automatically check the geometry management preferred by the actor
and return its preferred size depending on the value of the request-mode
property and on the natural size of the actor.</para></note>
property and on the natural size of the actor. The get_preferred_size()
method, though, will ignore any notion of "available size" so it should
not be used inside a <classname>ClutterActor</classname>::allocate()
implementation.</para></note>
<para>The size requisition starts from the #ClutterStage and it is
performed on every child of the stage following down the hierarchy
@ -154,11 +158,10 @@ foo_actor_init (FooActor *actor)
actor's scale, rotation or anchor point unless an actor is performing
layout management depending on those properties.</para></note>
<note><para>All the sizes are expressed using #ClutterUnit<!-- -->s, the
internal high-precision unit type, which guarantees sub-pixel precision.
#ClutterUnit currently has the same limitations that #ClutterFixed has,
see the <link linkend="clutter-Fixed-Point-Support">fixed point page</link>.
</para></note>
<note><para>All the sizes are expressed using pixels with subpixel
precision. The sub-pixel precision is useful when animating actors
but it can produce odd results on screen, so you might want to
truncate the precision of the computed values.</para></note>
<example id="clutter-actor-get-width-request-example">
<title>Width requisition implementation of a container</title>
@ -174,9 +177,9 @@ foo_actor_init (FooActor *actor)
<programlisting>
static void
foo_actor_get_preferred_width (ClutterActor *actor,
ClutterUnit for_height,
ClutterUnit *min_width_p,
ClutterUnit *natural_width_p)
gfloat for_height,
gfloat *min_width_p,
gfloat *natural_width_p)
{
GList *l;
ClutterUnit min_left, min_right;
@ -190,7 +193,7 @@ foo_actor_get_preferred_width (ClutterActor *actor,
for (l = children; l != NULL; l = l-&gt;next)
{
ClutterActor *child = l->data;
ClutterUnit child_x, child_min, child_natural;
gfloat child_x, child_min, child_natural;
child_x = clutter_actor_get_xu (child);
@ -270,64 +273,104 @@ foo_actor_get_preferred_width (ClutterActor *actor,
<note><para>The allocate() virtual function implementation will be
notified whether the actor has been moved, while clutter_actor_allocate()
will usually be invoked with a boolean flag meaning that the parent
has been moved.</para></note>
will usually be invoked with the %CLUTTER_ABSOLUTE_ORIGIN_CHANGED flag,
meaning that the parent has been moved.</para></note>
<example id="container-allocate-example">
<title>Allocation of a container</title>
<para>In this example, <classname>FooActor</classname> acts like a
horizontal box with overflowing, like a toolbar which will display
more children as it expands. The children falling outside of the
allocated area will fade out; the children falling inside the
same area will fade in.</para>
allocated area will not be allocated.</para>
<programlisting language="C">
static void
foo_actor_allocate (ClutterActor *actor,
const ClutterActorBox *box,
gboolean absolute_origin_changed)
foo_actor_allocate (ClutterActor *actor,
const ClutterActorBox *box,
ClutterAllocationFlags flags)
{
FooActor *foo_actor = FOO_ACTOR (actor);
ClutterUnit current_width;
gfloat available_width, available_height;
gfloat current_width, current_height;
gfloat row_height;
GList *l;
/* chain up to set the allocation of the actor */
CLUTTER_ACTOR_CLASS (foo_actor_parent_class)-&gt;allocate (actor, box, absolute_origin_changed);
/* chain up to store the allocation of the actor */
CLUTTER_ACTOR_CLASS (foo_actor_parent_class)-&gt;allocate (actor, box, flags);
current_width = foo_actor-&gt;padding;
clutter_actor_box_get_size (box,
&amp;available_width,
&amp;available_height);
current_width = 0;
current_height = 0;
row_height = 0;
for (l = foo_actor-&gt;children;
l != NULL;
l = l-&gt;next)
{
FooActorChild *child = l-&gt;data;
ClutterUnit natural_width, natural_height;
ClutterActor *child = l-&gt;data;
ClutterActorBox child_box = { 0, };
gfloat child_width, child_height;
ClutterRequestMode mode;
/* each child will get as much space as they require */
clutter_actor_get_preferred_size (CLUTTER_ACTOR (child),
NULL, NULL,
&amp;natural_width, &amp;natural_height);
/* do not allocate invisible children */
if (!CLUTTER_ACTOR_IS_VISIBLE (child))
continue;
/* if the child is overflowing, we just fade it out */
if (current_width + natual_width &gt; box-&gt;x2 - box-&gt;x1)
foo_actor_fade_child (foo_actor, child, 0);
else
g_object_get (G_OBJECT (child), "request-mode", &amp;mode, NULL);
if (mode == CLUTTER_REQUEST_HEIGHT_FOR_WIDTH)
{
current_width += natural_width + priv-&gt;padding;
gfloat min, natural;
child_box.x1 = current_width;
child_box.y1 = 0;
child_box.x2 = child_box.x1 + natural_width;
child_box.y2 = child_box.y1 + natural_height;
clutter_actor_get_preferred_width (child, available_height,
&amp;min, &amp;natural);
child_width = MAX (min, MIN (natural, available_width));
/* update the allocation */
clutter_actor_allocate (CLUTTER_ACTOR (child),
&amp;child_box,
absolute_origin_changed);
/* fade the child in if it wasn't visible */
foo_actor_fade_child (foo_actor, child, 255);
clutter_actor_get_preferred_height (child, child_width,
&amp;min, &amp;natural);
child_height = MAX (min, MIN (natural, available_height));
}
else (mode == CLUTTER_REQUEST_WIDTH_FOR_HEIGHT)
{
gfloat min, natural;
clutter_actor_get_preferred_height (child, available_width,
&amp;min, &amp;natural);
child_height = MAX (min, MIN (natural, available_height));
clutter_actor_get_preferred_width (child, child_height,
&amp;min, &amp;natural);
child_width = MAX (min, MIN (natural, available_width));
}
else
g_assert_not_reached ();
/* overflow */
if (current_width + child_width &gt; available_width)
{
current_width = 0;
current_height += row_height;
}
else
current_width += child_width;
/* stop allocating if we are overflowing the available height */
if (current_height + child_height &gt; available_height)
break;
child_box.x1 = current_width;
child_box.y1 = current_height;
child_box.x2 = child_box.x1 + child_width;
child_box.y2 = child_box.y1 + child_height;
/* update the allocation */
clutter_actor_allocate (child,
&amp;child_box,
flags);
row_height = MAX (row_height, child_height);
}
}
</programlisting>
@ -346,11 +389,6 @@ foo_actor_allocate (ClutterActor *actor,
using the Clutter GL and GLES abstraction library (COGL) or by directly
using the GL or GLES API.</para>
<note><para>Actors performing transformations should push the GL matrix
first and then pop the GL matrix before returning. COGL provides wrapper
functions for this operation, cogl_push_matrix() and cogl_pop_matrix().
</para></note>
<example id="simple-actor-paint-example">
<title>Paint implementation of a simple actor</title>
<para>In this example, the <classname>FooActor</classname>
@ -568,8 +606,9 @@ foo_actor_add_baz (FooActor *foo_actor,
<term>ClutterContainer::add</term>
<listitem>
<para>The container actor should hold a pointer to the passed
#ClutterActor, call clutter_actor_set_parent() on it and then
emit the #ClutterContainer::actor-added signal to notify
#ClutterActor, call clutter_actor_set_parent() on it, queue
a relayout on itself and then emit the
#ClutterContainer::actor-added signal to notify
handlers of the newly added actor.</para>
</listitem>
</varlistentry>
@ -593,9 +632,11 @@ foo_actor_add_baz (FooActor *foo_actor,
<varlistentry>
<term>ClutterContainer::foreach_with_internals</term>
<listitem>
<para>The contained should invoke the callback on every
<para>The container should invoke the callback on every
child it is holding, including eventual private children
that should not be handled by the #ClutterContainer API.</para>
that should not be handled by the #ClutterContainer API.
This method can be ignored if the container does not
have internal children.</para>
</listitem>
</varlistentry>
<varlistentry>
@ -603,7 +644,8 @@ foo_actor_add_baz (FooActor *foo_actor,
<listitem>
<para>The container should move the passed child on top
of the given sibling, or on top of the paint stack in
case the sibling is NULL.</para>
case the sibling is NULL. This method can be ignored if the
container does not have overlapping children.</para>
</listitem>
</varlistentry>
<varlistentry>
@ -611,14 +653,17 @@ foo_actor_add_baz (FooActor *foo_actor,
<listitem>
<para>The container should move the passed child below
the given sibling, or on the bottom of the paint stack
in case the sibling is NULL.</para>
in case the sibling is NULL. This method can be ignored
if the container does not have overlapping children.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>ClutterContainer::sort_depth_order</term>
<listitem>
<para>The container should sort the paint stack depending
on the relative depths of each child.</para>
on the relative depths of each child. This method can
be ignored if the container does not have overlapping
children.</para>
</listitem>
</varlistentry>
</variablelist>