NAME
XtCreateWidget, XtVaCreateWidget, XtCreateManagedWidget, XtVaCreateManagedWidget, XtDestroyWidget - create and destroy widgets
SYNTAX
Widget XtCreateWidget(String _n_a_m_e, WidgetClass _w_i_d_g_e_t___c_l_a_s_s,
Widget _p_a_r_e_n_t, ArgList _a_r_g_s, Cardinal _n_u_m___a_r_g_s);
Widget XtVaCreateWidget(String _n_a_m_e, WidgetClass _w_i_d_g_e_t___c_l_a_s_s,
Widget _p_a_r_e_n_t, ...);
Widget XtCreateManagedWidget(String _n_a_m_e, WidgetClass
_w_i_d_g_e_t___c_l_a_s_s, Widget _p_a_r_e_n_t, ArgList _a_r_g_s, Cardinal
_n_u_m___a_r_g_s);
Widget XtVaCreateManagedWidget(String _n_a_m_e, WidgetClass
_w_i_d_g_e_t___c_l_a_s_s, Widget _p_a_r_e_n_t, ...);
void XtDestroyWidget(Widget _w);
ARGUMENTS
-
_a_r_g_s
Specifies the argument list to override the resource defaults.
-
-
_n_a_m_e
Specifies the resource name for the created widget,
-
which is used for retrieving resources
and, for that reason, should not be the same as any other widget
that is a child of same parent.
-
_n_u_m___a_r_g_s
Specifies the number of arguments in the argument list.
-
-
_p_a_r_e_n_t
Specifies the parent widget.
-
-
_w
Specifies the widget.
-
-
_w_i_d_g_e_t___c_l_a_s_s
Specifies the widget class pointer for the created widget.
-
-
_._._.
Specifies the variable argument list to override the resource defaults.
-
DESCRIPTION
The
_X_t_C_r_e_a_t_e_W_i_d_g_e_t
function performs much of the boilerplate operations of widget creation:
-
·
Checks to see if the class_initialize procedure has been called for this class
-
and for all superclasses and, if not, calls those necessary in a
superclass-to-subclass order.
-
·
Allocates memory for the widget instance.
-
-
·
If the parent is a subclass of
-
_c_o_n_s_t_r_a_i_n_t_W_i_d_g_e_t_C_l_a_s_s,
it allocates 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 resource lists specified for this class and all superclasses.
-
·
If the parent is a subclass of
-
_c_o_n_s_t_r_a_i_n_t_W_i_d_g_e_t_C_l_a_s_s,
it initializes the resource fields of the constraints record
by using the constraint resource list specified for the parent's class
and all superclasses up to
_c_o_n_s_t_r_a_i_n_t_W_i_d_g_e_t_C_l_a_s_s.
-
·
Calls the initialize procedures for the widget by starting at the
-
_C_o_r_e
initialize procedure on down to the widget's initialize procedure.
-
·
If the parent is a subclass of
-
_c_o_m_p_o_s_i_t_e_W_i_d_g_e_t_C_l_a_s_s,
it puts the widget into its parent's children list by calling its parent's
insert_child procedure.
For further information,
see Section 3.5.
-
·
If the parent is a subclass of
-
_c_o_n_s_t_r_a_i_n_t_W_i_d_g_e_t_C_l_a_s_s,
it calls the constraint initialize procedures,
starting at
_c_o_n_s_t_r_a_i_n_t_W_i_d_g_e_t_C_l_a_s_s
on down to the parent's constraint initialize procedure.
Note that you can determine the number of arguments in an argument list
by using the
_X_t_N_u_m_b_e_r
macro.
For further information, see Section 11.1.
The
_X_t_C_r_e_a_t_e_M_a_n_a_g_e_d_W_i_d_g_e_t
function is a convenience routine that calls
_X_t_C_r_e_a_t_e_W_i_d_g_e_t
and
_X_t_M_a_n_a_g_e_C_h_i_l_d.
The
_X_t_D_e_s_t_r_o_y_W_i_d_g_e_t
function provides the only method of destroying a widget,
including widgets that need to destroy themselves.
It can be called at any time,
including from an application callback routine of the widget being destroyed.
This requires a two-phase destroy process in order to avoid dangling
references to destroyed widgets.
In phase one,
_X_t_D_e_s_t_r_o_y_W_i_d_g_e_t
performs the following:
-
·
If the being_destroyed field of the widget is
-
_T_r_u_e,
it returns immediately.
-
·
Recursively descends the widget tree and
-
sets the being_destroyed field to
_T_r_u_e
for the widget and all children.
-
·
Adds the widget to a list of widgets (the destroy list) that should be
-
destroyed when it is safe to do so.
Entries on the destroy list satisfy the invariant that
if w2 occurs after w1 on the destroy list then w2 is not a descendent of w1.
(A descendant refers to both normal and pop-up children.)
Phase two occurs when all procedures that should execute as a result of
the current event have been called (including all procedures registered with
the event and translation managers),
that is, when the current invocation of
_X_t_D_i_s_p_a_t_c_h_E_v_e_n_t
is about to return or immediately if not in
_X_t_D_i_s_p_a_t_c_h_E_v_e_n_t.
In phase two,
_X_t_D_e_s_t_r_o_y_W_i_d_g_e_t
performs the following on each entry in the destroy list:
-
·
Calls the destroy callback procedures registered on the widget
-
(and all descendants) in post-order (it calls children callbacks
before parent callbacks).
-
·
If the widget's parent is a subclass of
-
_c_o_m_p_o_s_i_t_e_W_i_d_g_e_t_C_l_a_s_s
and if the parent is not being destroyed,
it calls
_X_t_U_n_m_a_n_a_g_e_C_h_i_l_d
on the widget and then calls the widget's parent's delete_child procedure
(see Section 3.4).
-
·
If the widget's parent is a subclass of
-
_c_o_n_s_t_r_a_i_n_t_W_i_d_g_e_t_C_l_a_s_s,
it calls the constraint destroy procedure for the parent,
then the parent's superclass,
until finally it calls the constraint destroy procedure for
_c_o_n_s_t_r_a_i_n_t_W_i_d_g_e_t_C_l_a_s_s.
-
·
Calls the destroy methods for the widget (and all descendants)
-
in post-order.
For each such widget,
it calls the destroy procedure declared in the widget class,
then the destroy procedure declared in its superclass,
until finally it calls the destroy procedure declared in the Core
class record.
-
·
Calls
-
_X_D_e_s_t_r_o_y_W_i_n_d_o_w
if the widget is realized (that is, has an X window).
The server recursively destroys all descendant windows.
-
·
Recursively descends the tree and deallocates all pop-up widgets, constraint
-
records, callback lists and, if the widget is a subclass of
_c_o_m_p_o_s_i_t_e_W_i_d_g_e_t_C_l_a_s_s,
children.
SEE ALSO
XtAppCreateShell(3Xt),
XtCreatePopupShell(3Xt)
_X _T_o_o_l_k_i_t _I_n_t_r_i_n_s_i_c_s _- _C _L_a_n_g_u_a_g_e _I_n_t_e_r_f_a_c_e
_X_l_i_b _- _C _L_a_n_g_u_a_g_e _X _I_n_t_e_r_f_a_c_e