Provided by: libprima-perl_1.28-1.2_amd64 
NAME
Prima::Object - Prima toolkit base classes
SYNOPSIS
if ( $obj-> isa('Prima::Component')) {
# set and get a property
my $name = $obj-> name;
$obj->name( 'an object' );
# set a notification callback
$obj-> onPostMessage( sub {
shift;
print "hey! I've received this: @_\n";
});
# can set multiple properties. note, that 'name' and 'owner',
# replace the old values, while onPostMessage are aggregated.
$obj-> set(
name => 'AnObject',
owner => $new_owner,
onPostMessage => sub {
shift;
print "hey! me too!\n";
},
);
# de-reference by name
$new_owner-> AnObject-> post_message(1,2);
}
DESCRIPTION
Prima::Object and Prima::Component are the root objects of the Prima toolkit hierarchy. All the other
objects are derived from the Component class, which in turn is the only descendant of Object class. Both
of these classes are never used for spawning their instances, although this is possible using
Prima::Component-> create( .. parameters ... );
call. This document describes the basic concepts of the OO programming with Prima toolkit. Although
Component has wider functionality than Object, all examples will be explained on Component, since Object
has no descendant classes and all the functionality of Object is present in Component. Some of the
information here can be found in Prima::internals as well, the difference is that Prima::internals
considers the coding tasks from a C programmer's view, whereas this document is wholly about perl
programming.
Object base features
Creation
Object creation has fixed syntax:
$new_object = Class-> create(
parameter => value,
parameter => value,
...
);
Parameters and values form a hash, which is passed to the create() method. This hash is applied to a
default parameter-value hash ( a profile ), specific to every Prima class. The object creation is
performed in several stages.
create
create() calls profile_default() method that returns ( as its name states ) the default profile, a
hash with the appropriate default values assigned to its keys. The Component class defaults are (
see Classes.pm ):
name => ref $_[ 0],
owner => $::application,
delegations => undef,
While the exact meaning of these parameters is described later, in "Properties", the idea is that a
newly created object will have 'owner' parameter set to '$::application' and 'delegations' to undef
etc etc - unless these parameters are explicitly passed to create(). Example:
$a1 = Prima::Component-> create();
$a1's owner will be $::application
$a2 = Prima::Component-> create( owner => $a1);
$a2's owner will be $a1. The actual merging of the default and the parameter hashes is performed on
the next stage, in profile_check_in() method which is called inside profile_add() method.
profile_check_in
A profile_check_in() method merges the default and the parameter profiles. By default all specified
parameters have the ultimate precedence over the default ones, but in case the specification is
incomplete or ambiguous, the profile_check_in()'s task is to determine actual parameter values. In
case of Component, this method maintains a simple automatic naming of the newly created objects. If
the object name was not specified with create(), it is assigned to a concatenated class name with an
integer - Component1, Component2 etc.
Another example can be taken from Prima::Widget::profile_check_in(). Prima::Widget horizontal
position can be specified by using basic "left" and "width" parameters, and as well by auxiliary
"right", "size" and "rect". The default of both "left" and "width" is 100. But if only "right"
parameter, for example, was passed to create() it is profile_check_in() job to determine "left"
value, given that "width" is still 100.
After profiles gets merged, the resulting hash is passed to the third stage, init().
init
init() duty is to map the profile content into object, e.g., assign "name" property to "name"
parameter value, and so on - for all relevant parameters. After that, it has to return the profile
in order the overridden subsequent init() methods can perform same actions. This stage along with the
previous is exemplified in almost all Prima modules.
Note: usually init() attaches the object to its owner in order to keep the newly-created object
instance from being deleted by garbage-collection mechanisms. More on that later ( see "Links between
objects").
After init() finishes, create() calls setup() method
setup
setup() method is a convenience function, it is used when some post-init actions must be taken. It is
seldom overloaded, primarily because the Component::setup() method calls "onCreate" notification,
which is more convenient to overload than setup().
As can be noticed from the code pieces above, a successful create() call returns a newly created object.
If an error condition occurred, undef is returned. It must be noted, that only errors that were generated
via die() during init() stage result in undef. Other errors raise an exception instead. It is not
recommended to frame create() calls in an "eval{}" block, because the error conditions can only occur in
two situations. The first is a system error, either inside perl or Prima guts, and not much can be done
here, since that error can very probably lead to an unstable program and almost always signals an
implementation bug. The second reason is a caller's error, when an unexistent parameter key or invalid
value is passed; such conditions are not subject to a runtime error handling as are not the syntax
errors.
After create(), the object is subject to the event flow. As "onCreate" event is the first event the
object receives, only after that stage other events can be circulated.
Destruction
Object destruction can be caused by many conditions, but all execution flow is finally passed through
destroy() method. destroy(), as well as create() performs several finalizing steps:
cleanup
The first method called inside destroy() is cleanup(). cleanup() is the pair to setup(), as
destroy() is the pair to create(). cleanup() generates "onDestroy" event, which can be overridden
more easily than cleanup() itself.
"onDestroy" is the last event the object sees. After cleanup() no events are allowed to circulate.
done
done() method is the pair to init(), and is the place where all object resources are freed. Although
it is as safe to overload done() as init(), it almost never gets overloaded, primarily because
overloading "onDestroy" is easier.
The typical conditions that lead to object destructions are direct destroy() call, garbage collections
mechanisms, user-initiated window close ( on "Prima::Window" only ), and exception during init() stage.
Thus, one must be careful implementing done() which is called after init() throws an exception.
Methods
The class methods are declared and used with perl OO syntax, which allow both method of object
referencing:
$object-> method();
and
method( $object);
The actual code is a sub, located under the object class package. The overloaded methods that call their
ancestor code use
$object-> SUPER::method();
syntax. Most Prima methods have fixed number of parameters.
Properties
Properties are methods that combine functionality of two ephemeral "get" and "set" methods. The idea
behind properties is that many object parameters require two independent methods, one that returns some
internal state and another that changes it. For example, for managing the object name, set_name() and
get_name() methods are needed. Indeed, the early Prima implementation dealt with large amount of these
get's and set's, but later these method pairs were deprecated in the favor of properties. Currently,
there is only one method name() ( referred as "::name" later in the documentation ).
The property returns a value if no parameters ( except the object) are passed, and changes the internal
data to the passed parameters otherwise. Here's a sketch code for "::name" property implementation:
sub name
{
return $_[0]-> {name} unless $#_;
$_[0]->{name} = $_[1];
}
There are many examples of properties throughout the toolkit. Not all properties deal with scalar
values, some accept arrays or hashes as well. The properties can be set-called not only by name like
$object-> name( "new name");
but also with set() method. The set() method accepts a hash, that is much like to create(), and assigns
the values to the corresponding properties. For example, the code
$object-> name( "new name");
$object-> owner( $owner);
can be rewritten as
$object-> set(
name => "new name",
owner => $owner
);
A minor positive effect of a possible speed-up is gained by eliminating C-to-perl and perl-to-C calls,
especially if the code called is implemented in C. The negative effect of such technique is that the
order in which the properties are set, is undefined. Therefore, the usage of set() is recommended either
when the property order is irrelevant, or it is known beforehand that such a call speeds up the code, or
is an only way to achieve the result. An example of the latter case from Prima::internals shows that
Prima::Image calls
$image-> type( $a);
$image-> palette( $b);
and
$image-> palette( $b);
$image-> type( $a);
produce different results. It is indeed the only solution to call for such a change using
$image-> set(
type => $a,
palette => $b
);
when it is known beforehand that "Prima::Image::set" is aware of such combinations and calls neither
"::type" nor "::palette" but performs another image conversion instead.
Some properties are read-only and some are write-only. Some methods that might be declared as properties
are not; these are declared as plain methods with get_ or set_ name prefix. There is not much certainty
about what methods are better off being declared as properties and vice versa.
However, if get_ or set_ methods cannot be used in correspondingly write or read fashion, the R/O and W/O
properties can. They raise an exception on an attempt to do so.
Links between objects
Prima::Component descendants can be used as containers, as objects that are on a higher hierarchy level
than the others. This scheme is implemented in a child-owner relationship. The 'children' objects have
the "::owner" property value assigned to a reference to a 'owner' object, while the 'owner' object
conducts the list of its children. It is a one-to-many hierarchy scheme, as a 'child' object can have
only one owner, but an 'owner' object can have many children. The same object can be an owner and a child
at the same time, so the owner-child hierarchy can be viewed as a tree-like structure.
Prima::Component::owner property maintains this relation, and is writable - the object can change its
owner dynamically. There is no corresponding property that manages children objects, but is a method
get_components(), that returns an array of the child references.
The owner-child relationship is used in several ways in the toolkit. For example, the widgets that are
children of another widget appear ( usually, but not always ) in the geometrical interior of the owner
widget. Some events ( keyboard events, for example ) are propagated automatically up and/or down the
object tree. Another important feature is that when an object gets destroyed, its children are destroyed
first. In a typical program the whole object tree roots in a Prima::Application object instance. When
the application finishes, this feature helps cleaning up the widgets and quitting gracefully.
Implementation note: name 'owner' was taken instead of initial 'parent', because the 'parent' is a fixed
term for widget hierarchy relationship description. Prima::Widget relationship between owner and child is
not the same as GUI's parent-to-child. The parent is the widget for the children widgets located in and
clipped by its inferior. The owner widget is more than that, its children can be located outside its
owner boundaries.
The special convenience variety of create(), the insert() method is used to explicitly select owner of
the newly created object. insert() can be considered a 'constructor' in OO-terms. It makes the construct
$obj = Class-> create( owner => $owner, name => 'name);
more readable by introducing
$obj = $owner-> insert( 'Class', name => 'name');
scheme. These two code blocks are identical to each other.
There is another type of relation, where objects can hold references to each other. Internally this link
level is used to keep objects from deletion by garbage collection mechanisms. This relation is many-to-
many scheme, where every object can have many links to other objects. This functionality is managed by
attach() and detach() methods.
Events
Prima::Component descendants employ a well-developed event propagation mechanism, which allows handling
events using several different schemes. An event is a condition, caused by the system or the user, or an
explicit notify() call. The formerly described events onCreate and onDestroy are triggered after a new
object is created or before it gets destroyed. These two events, and the described below onPostMessage
are present in namespaces of all Prima objects. New classes can register their own events and define
their execution flow, using notification_types() method. This method returns all available information
about the events registered in a class.
Prima defines also a non-object event dispatching and filtering mechanism, available through "event_hook"
static method.
Propagation
The event propagation mechanism has three layers of user-defined callback registration, that are called
in different order and contexts when an event is triggered. The examples below show the usage of these
layers. It is assumed that an implicit
$obj-> notify("PostMessage", $data1, $data2);
call is issued for all these examples.
Direct methods
As it is usual in OO programming, event callback routines are declared as methods. 'Direct methods'
employ such a paradigm, so if a class method with name "on_postmessage" is present, it will be called
as a method ( i.e., in the object context ) when "onPostMessage" event is triggered. Example:
sub on_postmessage
{
my ( $self, $data1, $data2) = @_;
...
}
The callback name is a modified lower-case event name: the name for Create event is on_create,
PostMessage - on_postmessage etc. These methods can be overloaded in the object's class descendants.
The only note on declaring these methods in the first instance is that no "::SUPER" call is needed,
because these methods are not defined by default.
Usually the direct methods are used for the internal object book-keeping, reacting on the events that
are not designed to be passed higher. For example, a Prima::Button class catches mouse and keyboard
events in such a fashion, because usually the only notification that is interesting for the code that
employs push-buttons is "Click". This scheme is convenient when an event handling routine serves the
internal, implementation-specific needs.
Delegated methods
The delegated methods are used when objects ( mostly widgets ) include other dependent objects, and
the functionality requires interaction between these. The callback functions here are the same
methods as direct methods, except that they get called in context of two, not one, objects. If, for
example, a $obj's owner, $owner would be interested in $obj's PostMessage event, it would register
the notification callback by
$obj-> delegations([ $owner, 'PostMessage']);
where the actual callback sub will be
sub Obj_PostMessage
{
my ( $self, $obj, $data1, $data2) = @_;
}
Note that the naming style is different - the callback name is constructed from object name ( let
assume that $obj's name is 'Obj') and the event name. ( This is one of the reasons why
Component::profile_check_in() performs automatic naming of newly created onbjects). Note also that
context objects are $self ( that equals $owner ) and $obj.
The delegated methods can be used not only for the owner-child relations. Every Prima object is free
to add a delegation method to every other object. However, if the objects are in other than owner-
child relation, it is a good practice to add Destroy notification to the object which events are of
interest, so if it gets destroyed, the partner object gets a message about that.
Anonymous subroutines
The two previous callback types are more relevant when a separate class is developed, but it is not
necessary to declare a new class every time the event handling is needed. It is possible to use the
third and the most powerful event hook method using perl anonymous subroutines ( subs ) for the easy
customization.
Contrary to the usual OO event implementations, when only one routine per class dispatches an event,
and calls inherited handlers when it is appropriate, Prima event handling mechanism can accept many
event handlers for one object ( it is greatly facilitated by the fact that perl has anonymous subs,
however).
All the callback routines are called when an event is triggered, one by one in turn. If the direct
and delegated methods can only be multiplexed by the usual OO inheritance, the anonymous subs are
allowed to be multiple by the design. There are three syntaxes for setting such a event hook; the
example below sets a hook on $obj using each syntax for a different situation:
- during create():
$obj = Class-> create(
...
onPostMessage => sub {
my ( $self, $data1, $data2) = @_;
},
...
);
- after create using set()
$obj-> set( onPostMessage => sub {
my ( $self, $data1, $data2) = @_;
});
- after create using event name:
$obj-> onPostMessage( sub {
my ( $self, $data1, $data2) = @_;
});
As was noted in Prima, the events can be addressed as properties, with the exception that they are
not substitutive but additive. The additivity is that when the latter type of syntax is used, the
subs already registered do not get overwritten or discarded but stack in queue. Thus,
$obj-> onPostMessage( sub { print "1" });
$obj-> onPostMessage( sub { print "2" });
$obj-> notify( "PostMessage", 0, 0);
code block would print
21
as the execution result.
This, it is a distinctive feature of a toolkit is that two objects of same class may have different
set of event handlers.
Flow
When there is more than one handler of a particular event type present on an object, a question is risen
about what are callbacks call priorities and when does the event processing stop. One of ways to regulate
the event flow is based on prototyping events, by using notification_types() event type description.
This function returns a hash, where keys are the event names and the values are the constants that
describe the event flow. The constant can be a bitwise OR combination of several basic flow constants,
that control the three aspects of the event flow.
Order
If both anonymous subs and direct/delegated methods are present, it must be decided which callback
class must be called first. Both 'orders' are useful: for example, if it is designed that a class's
default action is to be overridden, it is better to call the custom actions first. If, on the
contrary, the class action is primary, and the others are supplementary, the reverse order is
preferred. One of two "nt::PrivateFirst" and "nt::CustomFirst" constants defines the order.
Direction
Almost the same as order, but for finer granulation of event flow, the direction constants
"nt::FluxNormal" and "nt::FluxReverse" are used. The 'normal flux' defines FIFO ( first in first out
) direction. That means, that the sooner the callback is registered, the greater priority it would
possess during the execution. The code block shown above
$obj-> onPostMessage( sub { print "1" });
$obj-> onPostMessage( sub { print "2" });
$obj-> notify( "PostMessage", 0, 0);
results in 21, not 12 because PostMessage event type is prototyped "nt::FluxReverse".
Execution control
It was stated above that the events are additive, - the callback storage is never discarded when
'set'-syntax is used. However, the event can be told to behave like a substitutive property, e.g. to
call one and only one callback. This functionality is governed by "nt::Single" bit in execution
control constant set, which consists of the following constants:
nt::Single
nt::Multiple
nt::Event
These constants are mutually exclusive, and may not appear together in an event type declaration. A
"nt::Single"-prototyped notification calls only the first ( or the last - depending on order and
direction bits ) callback. The usage of this constant is somewhat limited.
In contrary of "nt::Single", the "nt::Multiple" constant sets the execution control to call all the
available callbacks, with respect to direction and order bits.
The third constant, "nt::Event", is the impact as "nt::Multiple", except that the event flow can be
stopped at any time by calling clear_event() method.
Although there are 12 possible event type combinations, a half of them are not viable. Another half were
assigned to unique more-less intelligible names:
nt::Default ( PrivateFirst | Multiple | FluxReverse)
nt::Property ( PrivateFirst | Single | FluxNormal )
nt::Request ( PrivateFirst | Event | FluxNormal )
nt::Notification ( CustomFirst | Multiple | FluxReverse )
nt::Action ( CustomFirst | Single | FluxReverse )
nt::Command ( CustomFirst | Event | FluxReverse )
Success state
Events do not return values, although the event generator, the notify() method does - it returns either 1
or 0, which is the value of event success state. The 0 and 1 results in general do not mean either
success or failure, they simply reflect the fact whether clear_event() method was called during the
processing - 1 if it was not, 0 otherwise. The state is kept during the whole processing stage, and can
be accessed from Component::eventFlag property. Since it is allowed to call notify() inside event
callbacks, the object maintains a stack for those states. Component::eventFlags always works with the
topmost one, and fails if is called from outside the event processing stage. Actually, clear_event() is
an alias for ::eventFlag(0) call. The state stack is operated by push_event() and pop_event() methods.
Implementation note: a call of clear_event() inside a "nt::Event"-prototyped event call does not
automatically stops the execution. The execution stops if the state value equals to 0 after the callback
is finished. A ::eventFlag(1) call thus cancels the effect of clear_event().
A particular coding style is used when the event is "nt::Single"-prototyped and is called many times in a
row, so overheads of calling notify() become a burden. Although notify() logic is somewhat complicated,
it is rather simple with "nt::Single" case. The helper function get_notify_sub() returns the context of
callback to-be-called, so it can be used to emulate notify() behavior. Example:
for ( ... ) {
$result = $obj-> notify( "Measure", @parms);
}
can be expressed in more cumbersome, but efficient code if "nt::Single"-prototyped event is used:
my ( $notifier, @notifyParms) = $obj-> get_notify_sub( "Measure" );
$obj-> push_event;
for ( ... ) {
$notifier-> ( @notifyParms, @parms);
# $result = $obj-> eventFlag; # this is optional
}
$result = $obj-> pop_event;
API
Prima::Object methods
alive
Returns the object 'vitality' state - true if the object is alive and usable, false otherwise. This
method can be used as a general checkout if the scalar passed is a Prima object, and if it is usable.
The true return value can be 1 for normal and operational object state, and 2 if the object is alive
but in its init() stage. Example:
print $obj-> name if Prima::Object::alive( $obj);
can NAME, CACHE = 1
Checks if an object namespace contains a NAME method. Returns the code reference to it, if found,
and undef if not. If CACHE is true, caches the result to speed-up subsequent calls.
cleanup
Called right after destroy() started. Used to initiate "cmDestroy" event. Is never called directly.
create CLASS, %PARAMETERS
Creates a new object instance of a given CLASS and sets its properties corresponding to the passed
parameter hash. Examples:
$obj = Class-> create( PARAMETERS);
$obj = Prima::Object::create( "class" , PARAMETERS);
Is never called in an object context.
Alias: new()
destroy
Initiates the object destruction. Perform in turn cleanup() and done() calls. destroy() can be
called several times and is the only Prima re-entrant function, therefore may not be overloaded.
done
Called by destroy() after cleanup() is finished. Used to free the object resources, as a finalization
stage. During done() no events are allowed to circulate, and alive() returns 0. The object is not
usable after done() finishes. Is never called directly.
Note: the eventual child objects are destroyed inside done() call.
get @PARAMETERS
Returns hash where keys are @PARAMETERS and values are the corresponding object properties.
init %PARAMETERS
The most important stage of object creation process. %PARAMETERS is the modified hash that was
passed to create(). The modification consists of merging with the result of profile_default() class
method inside profile_check_in() method. init() is responsible for applying the relevant data into
PARAMETERS to the object properties. Is never called directly.
insert CLASS, %PARAMETERS
A convenience wrapper for create(), that explicitly sets the owner property for a newly created
object.
$obj = $owner-> insert( 'Class', name => 'name');
is adequate to
$obj = Class-> create( owner => $owner, name => 'name);
code. insert() has another syntax that allows simultaneous creation of several objects:
@objects = $owner-> insert(
[ 'Class', %parameters],
[ 'Class', %parameters],
...
);
With such syntax, all newly created objects would have $owner set to their 'owner' properties.
new CLASS, %PARAMETERS
Same as create.
profile_add PROFILE
The first stage of object creation process. PROFILE is a reference to a PARAMETERS hash, passed to
create(). It is merged with profile_default() after passing both to profile_check_in(). The merge
result is stored back in PROFILE. Is never called directly.
profile_check_in CUSTOM_PROFILE, DEFAULT_PROFILE
The second stage of object creation process. Resolves eventual ambiguities in CUSTOM_PROFILE, which
is the reference to PARAMETERS passed to create(), by comparing to and using default values from
DEFAULT_PROFILE, which is the result of profile_default() method. Is never called directly.
profile_default
Returns hash of the appropriate default values for all properties of a class. In object creation
process serves as a provider of fall-back values, and is called implicitly. This method can be used
directly, contrary to the other creation process-related functions.
Can be called in a context of class.
raise_ro TEXT
Throws an exception with text TEXT when a read-only property is called in a set- context.
raise_wo TEXT
Throws an exception with text TEXT when a write-only property is called in a get- context.
set %PARAMETERS
The default behavior is an equivalent to
sub set
{
my $obj = shift;
my %PARAMETERS = @_;
$obj-> $_( $PARAMETERS{$_}) for keys %PARAMETERS;
}
code. Assigns object properties correspondingly to PARAMETERS hash. Many Prima::Component
descendants overload set() to make it more efficient for particular parameter key patterns.
As the code above, raises an exception if the key in PARAMETERS has no correspondent object property.
setup
The last stage of object creation process. Called after init() finishes. Used to initiate "cmCreate"
event. Is never called directly.
Prima::Component methods
add_notification NAME, SUB, REFERER = undef, INDEX = -1
Adds SUB to the list of notification of event NAME. REFERER is the object reference, which is used
to create a context to SUB and is passed as a parameter to it when called. If REFERER is undef ( or
not specified ), the same object is assumed. REFERER also gets implicitly attached to the object, -
the implementation frees the link between objects when one of these gets destroyed.
INDEX is a desired insert position in the notification list. By default it is -1, what means 'in the
start'. If the notification type contains nt::FluxNormal bit set, the newly inserted SUB will be
called first. If it has nt::FluxReverse, it is called last, correspondingly.
Returns positive integer value on success, 0 on failure. This value can be later used to refer to
the SUB in remove_notification().
See also: "remove_notification", "get_notification".
attach OBJECT
Inserts OBJECT to the attached objects list and increases OBJECT's reference count. The list can not
hold more than one reference to the same object. The warning is issued on such an attempt.
See also: "detach".
bring NAME
Looks for a immediate child object that has name equals to NAME. Returns its reference on success,
undef otherwise. It is a convenience method, that makes possible the usage of the following
constructs:
$obj-> name( "Obj");
$obj-> owner( $owner);
...
$owner-> Obj-> destroy;
can_event
Returns true if the object event circulation is allowed. In general, the same as "alive() == 1",
except that can_event() fails if an invalid object reference is passed.
clear_event
Clears the event state, that is set to 1 when the event processing begins. Signals the event
execution stop for nt::Event-prototyped events.
See also: "Events", "push_event", "pop_event", "::eventFlag", "notify".
detach OBJECT, KILL
Removes OBJECT from the attached objects list and decreases OBJECT's reference count. If KILL is
true, destroys OBJECT.
See also: "attach"
event_error
Issues a system-dependent warning sound signal.
event_hook [ SUB ]
Installs a SUB to receive all events on all Prima objects. SUB receives same parameters passed to
notify, and must return an integer, either 1 or 0, to pass or block the event respectively.
If no SUB is set, returns currently installed event hook pointer. If SUB is set, replaces the old
hook sub with SUB. If SUB is 'undef', event filtering is not used.
Since the 'event_hook' mechanism allows only one hook routine to be installed at a time, direct usage
of the method is discouraged. Instead, use Prima::EventHook for multiplexing of the hook access.
The method is static, and can be called either with or without class or object as a first parameter.
get_components
Returns array of the child objects.
See: "create", "Links between objects".
get_handle
Returns a system-dependent handle for the object. For example, Prima::Widget return its system
WINDOW/HWND handles, Prima::DeviceBitmap - its system PIXMAP/HBITMAP handles, etc.
Can be used to pass the handle value outside the program, for an eventual interprocess communication
scheme.
get_notification NAME, @INDEX_LIST
For each index in INDEX_LIST return three scalars, bound at the index position in the NAME event
notification list. These three scalars are REFERER, SUB and ID. REFERER and SUB are those passed to
"add_notification", and ID is its result.
See also: "remove_notification", "add_notification".
get_notify_sub NAME
A convenience method for nt::Single-prototyped events. Returns code reference and context for the
first notification sub for event NAME.
See "Success state" for example.
notification_types
Returns a hash, where the keys are the event names and the values are the "nt::" constants that
describe the event flow.
Can be called in a context of class.
See "Events" and "Flow" for details.
notify NAME, @PARAMETERS
Calls the subroutines bound to the event NAME with parameters @PARAMETERS in context of the object.
The calling order is described by "nt::" constants, contained in the notification_types() result
hash.
notify() accepts variable number of parameters, and while it is possible, it is not recommended to
call notify() with the exceeding number of parameters; the call with the deficient number of
parameters results in an exception.
Example:
$obj-> notify( "PostMessage", 0, 1);
See "Events" and "Flow" for details.
pop_event
Closes event processing stage brackets.
See "push_event", "Events"
post_message SCALAR1, SCALAR2
Calls "PostMessage" event with parameters SCALAR1 and SCALAR2 once during idle event loop. Returns
immediately. Does not guarantee that "PostMessage" will be called, however.
See also "post" in Prima::Utils
push_event
Opens event processing stage brackets.
See "pop_event", "Events"
remove_notification ID
Removes a notification subroutine that was registered before with "add_notification", where ID was
its result. After successful removal, the eventual context object gets implicitly detached from the
storage object.
See also: "add_notification", "get_notification".
set_notification NAME, SUB
Adds SUB to the event NAME notification list. Almost never used directly, but is a key point in
enabling the following notification add syntax
$obj-> onPostMessage( sub { ... });
or
$obj-> set( onPostMessage => sub { ... });
that are shortcuts for
$obj-> add_notification( "PostMessage", sub { ... });
unlink_notifier REFERER
Removes all notification subs from all event lists bound to REFERER object.
Prima::Component properties
eventFlag STATE
Provides access to the last event processing state in the object event state stack.
See also: "Success state", "clear_event", "Events".
delegations [ <REFERER>, NAME, <NAME>, < <REFERER>, NAME, ... > ]
Accepts an anonymous array in set- context, which consists of a list of event NAMEs, that a REFERER
object ( the caller object by default ) is interested in. Registers notification entries for
routines if subs with naming scheme REFERER_NAME are present on REFERER name space. The example code
$obj-> name("Obj");
$obj-> delegations([ $owner, 'PostMessage']);
registers Obj_PostMessage callback if it is present in $owner namespace.
In get- context returns an array reference that reflects the object's delegated events list content.
See also: "Delegated methods".
name NAME
Maintains object name. NAME can be an arbitrary string, however it is recommended against usage of
special characters and spaces in NAME, to facilitate the indirect object access coding style:
$obj-> name( "Obj");
$obj-> owner( $owner);
...
$owner-> Obj-> destroy;
and to prevent system-dependent issues. If the system provides capabilities that allow to predefine
some object parameters by its name ( or class), then it is impossible to know beforehand the system
naming restrictions. For example, in X window system the following resource string would make all
Prima toolkit buttons green:
Prima*Button*backColor: green
In this case, using special characters such as ":" or "*" in the name of an object would make the X
resource unusable.
owner OBJECT
Selects an owner of the object, which may be any Prima::Component descendant. Setting an owner to a
object does not alter its reference count. Some classes allow OBJECT to be undef, while some do not.
All widget objects can not exist without a valid owner; Prima::Application on the contrary can only
exist with owner set to undef. Prima::Image objects are indifferent to the value of the owner
property.
Changing owner dynamically is allowed, but it is a main source of implementation bugs, since the
whole hierarchy tree is needed to be recreated. Although this effect is not visible in perl, the
results are deeply system-dependent, and the code that changes owner property should be thoroughly
tested.
Changes to "owner" result in up to three notifications: "ChangeOwner", which is called to the object
itself, "ChildLeave", which notifies the previous owner that the object is about to leave, and
"ChildEnter", telling the new owner about the new child.
Prima::Component events
ChangeOwner OLD_OWNER
Called at runtime when the object changes its owner.
ChildEnter CHILD
Triggered when a child object is attached, either as a new instance or as a result of runtime owner
change.
ChildLeave CHILD
Triggered when a child object is detached, either because it is getting destroyed or as a result of
runtime owner change.
Create
The first event an event sees. Called automatically after init() is finished. Is never called
directly.
Destroy
The last event an event sees. Called automatically before done() is started. Is never called
directly.
PostMessage SCALAR1, SCALAR2
Called after post_message() call is issued, not inside post_message() but at the next idle event
loop. SCALAR1 and SCALAR2 are the data passed to post_message().
AUTHOR
Dmitry Karasik, <dmitry@karasik.eu.org>.
SEE ALSO
Prima, Prima::internals, Prima::EventHook.