XtCreateWidget man page on HP-UX

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XtCreateWidget()					      XtCreateWidget()

Name
  XtCreateWidget - create an instance of a widget.

Synopsis
  Widget XtCreateWidget(name, object_class, parent, args, num_args)
	 String name;
	 WidgetClass object_class;
	 Widget parent;
	 ArgList args;
	 Cardinal num_args;

Inputs
  name	    Specifies the resource name for the created object.

  object_class
	    Specifies  the  widget  class pointer for the created widget;
	    may be objectClass or any subclass.

  parent    Specifies the parent widget; may be of class  objectClass  or
	    any subclass thereof.

  args	    Specifies	the   argument	list  to  override  the	 resource
	    defaults.

  num_args  Specifies the number of arguments in the argument list.

Returns
  An child widget or object of parent of class object_class.

Description
  XtCreateWidget() creates a new instance  of  class  object_class  named
  name,	 as a child of parent.	The resource name/resource value pairs in
  args are used to set resources in the	 widget	 and  override	resources
  from	the resource database.	The details of the widget creation proce‐
  dure are explained in the "Algorithm" section below.

Usage
  A created widget will not be visible until it is managed.  You can man‐
  age  a  child widget with XtManageChild(), and you can combine the call
  to XtCreateWidget() and XtManageChild() by calling  XtCreateManagedWid‐
  get(). Note that you cannot manage direct subclasses of Object.

  A  created  and  managed  widget will not be visible unless it has been
  realized (i.e., had an X window created).   You  realize  a  widget  by
  calling  XtRealizeWidget(), which realizes the specified widget and all
  of its children.  If you create a child of a realized widget, the child
  is  automatically  realized.	You will generally call XtRealizeWidget()
  once in an application, just before entering your main event loop.

  Rather than initialize an ArgList and pass it to XtCreateWidget(),  you
  can  call  XtVaCreateWidget()	 or  XtVaCreateManagedWidget() which both
  accept a NULL-terminated variable  length  argument  list  of	 resource
  names and resource values.

  To create a popup widget, you must use XtCreatePopupShell() rather than
  XtCreateWidget().

  You may give your widgets any name you want, and may give multiple wid‐
  gets	the  same  name.  If two sibling widgets have the same name, how‐
  ever, they will get the same resources from the resource database,  and
  it is undefined which will be returned by a call to XtNameToWidget().

  XtCreateWidget()  allows  you	 to create child widgets of non-Composite
  widgets.  If you do this, the child widget will not appear on any chil‐
  dren list in the parent and will not be automatically realized when its
  parent is realized or destroyed when its parent is destroyed.	 The only
  time	you  should  do	 this is when writing a non-Composite widget that
  explicitly creates and manages its own children.

Algorithm
  XtCreateWidget() does the  following	when  creating	a  widget  or  an
  object:

  ·  Checks  to	 see if the class_initialize() method has been called for
     this class and for all superclasses and, if not, calls those  neces‐
     sary in a superclass-to-subclass order.

  ·  If the specified class is not coreWidgetClass or a subclass thereof,
     and the parent's class is a  subclass  of	compositeWidgetClass  and
     either  no	 extension  record  in	the parent's composite class part
     extension	field  exists  with  the  record_type  NULLQUARK  or  the
     accepts_objects field in the extension record is False, XtCreateWid‐
     get() issues a fatal error.

  ·  Allocates memory for the widget instance.

  ·  If the parent is a member of the class constraintWidgetClass,  allo‐
     cates  memory for the parent's constraints and stores the address of
     this memory into the constraints field.

  ·  Initializes the Core nonresource data fields  (for	 example,  parent
     and visible).

  ·  Initializes  the  resource fields (for example, background_pixel) by
     using the CoreClassPart resource lists specified for this class  and
     all superclasses.

  ·  If	 the  parent is a member of the class constraintWidgetClass, ini‐
     tializes the resource fields of the constraints record by using  the
     ConstraintClassPart  resource lists specified for the parent's class
     and all superclasses up to constraintWidgetClass.

  ·  Calls the initialize() methods for the widget in  superclass-to-sub‐
     class order.

  ·  If	 the  parent  is a member of the class compositeWidgetClass, puts
     the widget into its parent's children list by calling  its	 parent's
     insert_child() method.

  ·  If	 the parent is a member of the class constraintWidgetClass, calls
     the ConstraintClassPart initialize() methods, in  superclass-to-sub‐
     class order.

  XtCreateWidget()  converts  and caches resources in a way equivalent to
  XtConvertAndStore() when initializing	 the  object  instance.	  Because
  there	 is  extra memory overhead required to implement reference count‐
  ing, clients may distinguish those objects  that  are	 never	destroyed
  before the application exits from those that may be destroyed and whose
  resources should be deallocated.

  To specify  whether  reference  counting  is	to  be	enabled	 for  the
  resources of a particular object when the object is created, the client
  can specify a value for the Boolean resource XtNinitialResourcesPersis‐
  tent, class XtCInitialResourcesPersistent.

  When	XtCreateWidget()  is called, if this resource is not specified as
  False in  either  the	 arglist  or  the  resource  database,	then  the
  resources  referenced by this object are not reference-counted, regard‐
  less of how the type converter may have been registered.  The effective
  default  value is True; thus clients that expect to destroy one or more
  objects and want resources deallocated must  explicitly  specify  False
  for XtNinitialResourcesPersistent

  The  resources  are still freed and destructors called when XtCloseDis‐
  play() is called if the conversion was registered as XtCacheByDisplay.

See Also
  XtCreateManagedWidget(1), XtVaCreateWidget(1), XtVaCreateManagedWid‐
  get(1).

Xt - Widget Lifecycle					      XtCreateWidget()
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