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       Prima::VB::Classes - Visual Builder widgets and types


       Visual Builder is designed without a prior knowledge of the widget classes that would be
       contained in its widget palette.  Instead, it provides a registration interface for new
       widgets and their specific properties.

       This document describes API, provided by the builder, and the widget interface. Through
       the document, widget or widget class mean not the original widget or class, but their


       The widget must provide specific methods to cooperate with the builder.  It is not
       required, however, to contain these methods in its base module or package; it can delegate
       its representation to another, usually very light class, which is used by the builder.

       Such a class must be derived from "Prima::VB::Object", which provides base functionality.
       One of basic features here is overloading of property change method. Since the user can
       change any property interactively, the class can catch the properties of interest by
       declaring "prf_XXX" method, where XXX is the property name. "Prima::VB::Widget" declares
       set of these methods, assuming that a widget would repaint when, for example, its "color"
       or "font" properties change.

       The hierarchy of VB classes mimics the one of the core toolkit classes, but this is a mere
       resemblance, no other dependencies except the names are present. The hierarchy is as

               Prima::VB::Object   Prima::Widget

       NB: "Prima::VB::CoreClasses" extends the hierarchy to the full set of default widget
       palette in the builder. This module is not provided with documentation though since its
       function is obvious and its code is trivial.

       Since the real widgets are used in the interaction with the builder, their properties are
       not touched when changed by the object inspector or otherwise. The widgets keep the set of
       properties in a separated hash. The properties are accessible by "prf" and "prf_set"

       A type object is a class used to represent a particular type of property in object
       inspector window in the builder.  The type objects, like the widget classes, also are not
       hard-coded. The builder presents a basic set of the type objects, which can be easily
       expanded.  The hierarchy ( incomplete ) of the type objects classes is as follows:


       The document does not describe the types, since their function can be observed at runtime
       in the object inspector.  Only "Prima::VB::Types::generic" API is documented.


       class STRING
           Selects the original widget class. Create-only property.

       creationOrder INTEGER
           Selects the creation order of the widget.

       module STRING
           Selects the module that contains the original widget class. Create-only property.

       profile HASH
           Selects the original widget profile. Create-only property.  Changes to profile at run-
           time performed by "prf_set" method.

           Returns hash of callbacks to be stored in the form file and executed by
           "Prima::VB::VBLoader" when the form file is loaded.  The hash keys are names of
           VBLoader events and values - strings with code to be eval'ed. See "Events" in
           Prima::VB::VBLoader for description and format of the callbacks.

           Called when the builder writes a form file.

       add_hooks @PROPERTIES
           Registers the object as a watcher to set of PROPERTIES.  When any object changes a
           property listed in the hook record, "on_hook" callback is triggered.

           Special name 'DESTROY' can be used to set a hook on object destruction event.

           Returns a class-specific hash, written in a form file.  Its use is to serve as a set
           of extra parameters, passed from the builder to "act_profile" events.

       prf_set %PROIFLE
           A main method for setting a property of an object.  PROFILE keys are property names,
           and value are property values.

       prf_adjust_default PROFILE, DEFAULT_PROFILE
           DEFAULT_PROFILE is a result of "profile_default" call of the real object class.
           However, not all properties usually are exported to the object inspector.
           "prf_adjust_default" deletes the unneeded property keys from PROFILE hash.

       prf_delete @PROPERTIES
           Removes PROPERTIES from internal properties hash.  This action results in that the
           PROPERTIES in the object inspector are set back to their default values.

           Returns hash of a class-specific events. These appear in the object inspector on
           "Events" page. The hash keys are event names; the hash values are default code pieces,
           that describe format of the event parameters. Example:

                   sub prf_events { return (
                           $_[0]-> SUPER::prf_events,
                           onSelectItem  => 'my ( $self, $index, $selectState) = @_;',

       prf @PROPERTIES
           Maps array of PROPERTIES names to their values. If called in scalar context, returns
           the first value only; if in array context, returns array of property values.

           Returns an anonymous hash, where keys are names of the type class without
           "Prima::VB::Types::" prefix, and values are arrays of property names.

           This callback returns an inverse mapping of properties by the types.

       prf_types_add PROFILE1, PROFILE2
           Adds PROFILE2 content to PROFILE1. PROFILE1 and PROFILE2 are hashes in format of
           result of "prf_types" method.

       prf_types_delete PROFILE, @NAMES
           Removes @NAMES from PROFILE. Need to be called if property type if redefined through
           the inheritance.

       remove_hooks @PROPERTIES
           Cancels watch for set of PROPERTIES.

           Called for all objects, registered as watchers by "add_hooks" when PROPERTY on object
           NAME is changed from OLD_VALUE to NEW_VALUE. Special PROPERTY 'DESTROY' hook is called
           when object NAME is destroyed.


       marked MARKED , EXCLUSIVE
           Selects marked state of a widget. If MARKED flag is 1, the widget is selected as
           marked. If 0, it is selected as unmarked.  If EXCLUSIVE flag is set to 1, then all
           marked widgets are unmarked before the object mark flag is set.

       sizeable BOOLEAN
           If 1, the widget can be resized by the user.  If 0, in can only be moved.

       mainEvent STRING
           Selects the event name, that will be opened in the object inspector when the user
           double clicks on the widget.

       common_paint CANVAS
           Draws selection and resize marks on the widget if it is in the selected state. To be
           called from all "on_paint" callbacks.

           Returns offset to the owner widget. Since the builder does not insert widgets in
           widgets to reflect the user-designed object hierarchy, this method is to be used to
           calculate children widgets relative positions.

       xy2part X, Y
           Maps X, Y point into part of widget. If result is not equal to 'client' string, the
           event in X, Y point must be ignored.

       iterate_children SUB, @ARGS
           Traverses all children widget in the hierarchy, calling SUB routine with widget, self,
           and @ARGS parameters on each.

           Invokes an alternative, class-specific popup menu, if present.  The popup object must
           be named 'AltPopup'.

           Called when the widget is loaded from a file or the clipboard.


       Root of all type classes.

       A type class can be used with and without object instance. The instantiated class contains
       reference to ID string, which is a property name that the object presents in the object
       inspector, and WIDGET, which is the property applied to. When the object inspector
       switches widgets, the type object is commanded to update the references.

       A class must also be usable without object instance, in particular, in "write" method. It
       is called to export the property value in a storable format as a string, better as a perl-
       evaluable expression.

           Constructor method. CONTAINER is a panel widget in the object inspector, where the
           type object can insert property value selector widgets.

       renew ID, WIDGET
           Resets property name and the widget.

       quotable STRING
           Returns quotable STRING.

       printable STRING
           Returns a string that can be stored in a file.

           Called when the widget property value is changed.

           Called when the property name ( ID ) is changed.  The type object may consider update
           its look or eventual internal variables on this event.

       get Returns property value, based on the selector widgets value.

           Called when the type object is to be visualized first time.  The object must create
           property value selector widgets in the "{container}" panel widget.

           Returns array of strings of modules, needed to be pre-loaded before a form file with
           type class-specific information can be loaded.  Usually it is used when "write" method
           exports constant values, which are defined in another module.

       set DATA
           Called when a new value is set to the widget property by means other than the selector
           widgets, so these can be updated. DATA is the property new value.

           Checks internal state of data and returns a boolean flag, if the type object data can
           be exported and set to widget profile.

       write CLASS, ID, DATA
           Called when DATA is to be written in form.  "write" must return such a string that can
           be loaded by "Prima::VB::VBLoader" later.


       Dmitry Karasik, <>.


       VB, Prima::VB::VBLoader, Prima::VB::CfgMaint.