path: root/docs/reference/gtk/tmpl/gtkcontainer.sgml

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GtkContainer

<!-- ##### SECTION Short_Description ##### -->
Base class for widgets which contain other widgets

<!-- ##### SECTION Long_Description ##### -->
<para>
A GTK+ user interface is constructed by nesting widgets inside widgets. 
Container widgets are the inner nodes in the resulting tree of widgets: 
they contain other widgets. So, for example, you might have a #GtkWindow 
containing a #GtkFrame containing a GtkLabel. If you wanted an image instead 
of a textual label inside the frame, you might replace the #GtkLabel widget 
with a #GtkImage widget.
</para>
<para>
There are two major kinds of container widgets in GTK+. Both are subclasses 
of the abstract #GtkContainer base class.
</para>
<para>
The first type of container widget has a single child widget and derives 
from #GtkBin. These containers are <firstterm>decorators</firstterm>, which 
add some kind of functionality to the child. For example, a #GtkButton makes 
its child into a clickable button; a #GtkFrame draws a frame around its child 
and a #GtkWindow places its child widget inside a top-level window.
</para>
<para>
The second type of container can have more than one child; its purpose is to 
manage <firstterm>layout</firstterm>. This means that these containers assign 
sizes and positions to their children. For example, a #GtkHBox arranges its 
children in a horizontal row, and a #GtkTable arranges the widgets it contains 
in a two-dimensional grid. 
</para>
<para>
To fulfill its task, a layout container must negotiate the size requirements 
with its parent and its children. This negotiation is carried out in two 
phases, <firstterm>size requisition</firstterm> and <firstterm>size 
allocation</firstterm>. 
</para>
<refsect2 id="size-requisition"><title>Size Requisition</title>
<para>
The size requisition of a widget is it's desired width and height. 
This is represented by a #GtkRequisition.
</para>
<para>
How a widget determines its desired size depends on the widget. 
A #GtkLabel, for example, requests enough space to display all its text. 
Container widgets generally base their size request on the requisitions 
of their children.  
</para>
<para>
The size requisition phase of the widget layout process operates top-down. 
It starts at a top-level widget, typically a #GtkWindow. The top-level widget 
asks its child for its size requisition by calling gtk_widget_size_request(). 
To determine its requisition, the child asks its own children for their 
requisitions and so on. Finally, the top-level widget will get a requisition 
back from its child. 
</para>
</refsect2>
<refsect2 id="size-allocation"><title>Size Allocation</title>
<para>
When the top-level widget has determined how much space its child would like 
to have, the second phase of the size negotiation, size allocation, begins. 
Depending on its configuration (see gtk_window_set_resizable()), the top-level 
widget may be able to expand in order to satisfy the size request or it may 
have to ignore the size request and keep its fixed size. It then tells its 
child widget how much space it gets by calling gtk_widget_size_allocate(). 
The child widget divides the space among its children and tells each child 
how much space it got, and so on. Under normal circumstances, a #GtkWindow 
will always give its child the amount of space the child requested.
</para>
<para>
A child's size allocation is represented by a #GtkAllocation. This struct 
contains not only a width and height, but also a position (i.e. X and Y 
coordinates), so that containers can tell their children not only how much
space they have gotten, but also where they are positioned inside the space 
available to the container. 
</para>
<para>
Widgets are required to honor the size allocation they receive; a size 
request is only a request, and widgets must be able to cope with any size.
</para>
</refsect2>
<refsect2 id="child-properties"><title>Child properties</title>
<para>
<structname>GtkContainer</structname> introduces <firstterm>child 
properties</firstterm> - these are object properties that are not specific
to either the container or the contained widget, but rather to their relation.
Typical examples of child properties are the position or pack-type of a widget
which is contained in a #GtkBox.</para>
<para>
Use gtk_container_class_install_child_property() to install child properties 
for a container class and gtk_container_class_find_child_property() or
gtk_container_class_list_child_properties() to get information about existing
child properties.
</para>
<para>
To set the value of a child property, use gtk_container_child_set_property(), 
gtk_container_child_set() or gtk_container_child_set_valist(). 
To obtain the value of a child property, use 
gtk_container_child_get_property(), gtk_container_child_get() or
gtk_container_child_get_valist(). To emit notification about child property 
changes, use gtk_widget_child_notify().
</para>
</refsect2>

<refsect2 id="GtkContainer-BUILDER-UI">
<title>GtkContainer as GtkBuildable</title>
<para>
The GtkContainer implementation of the GtkBuildable interface 
supports a &lt;packing&gt; element for children, which can
contain multiple &lt;property&gt; elements that specify
child properties for the child.
</para>
<example>
<title>Child properties in UI definitions</title>
<programlisting><![CDATA[
<object class="GtkVBox">
  <child>
    <object class="GtkLabel"/>
    <packing>
      <property name="pack-type">start</property>
    </packing>
  </child>
</object>
]]></programlisting>
</example>
<para>
Since 2.16, child properties can also be marked as translatable using
the same "translatable", "comments" and "context" attributes that are used
for regular properties.
</para>
</refsect2>

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<para>

</para>

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<!-- ##### STRUCT GtkContainer ##### -->
<para>

</para>


<!-- ##### SIGNAL GtkContainer::add ##### -->
<para>

</para>

@container: the object which received the signal.
@widget: 

<!-- ##### SIGNAL GtkContainer::check-resize ##### -->
<para>

</para>

@container: the object which received the signal.

<!-- ##### SIGNAL GtkContainer::remove ##### -->
<para>

</para>

@container: the object which received the signal.
@widget: 

<!-- ##### SIGNAL GtkContainer::set-focus-child ##### -->
<para>

</para>

@container: the object which received the signal.
@widget: 

<!-- ##### ARG GtkContainer:border-width ##### -->
<para>

</para>

<!-- ##### ARG GtkContainer:child ##### -->
<para>

</para>

<!-- ##### ARG GtkContainer:resize-mode ##### -->
<para>

</para>

<!-- ##### MACRO GTK_IS_RESIZE_CONTAINER ##### -->
<para>

</para>

@widget: 


<!-- ##### MACRO GTK_CONTAINER_WARN_INVALID_CHILD_PROPERTY_ID ##### -->
<para>
This macro should be used to emit a standard warning about unexpected
properties in set_child_property() and get_child_property() implementations.
</para>

@object: the #GObject on which set_child_property() or get_child_property() 
   was called
@property_id: the numeric id of the property
@pspec: the #GParamSpec of the property


<!-- ##### MACRO gtk_container_border_width ##### -->
<para>
Does the same as gtk_container_set_border_width().
</para>

@Deprecated: Use gtk_container_set_border_width() instead.


<!-- ##### FUNCTION gtk_container_add ##### -->
<para>

</para>

@container: 
@widget: 


<!-- ##### FUNCTION gtk_container_remove ##### -->
<para>

</para>

@container: 
@widget: 


<!-- ##### FUNCTION gtk_container_add_with_properties ##### -->
<para>

</para>

@container: 
@widget: 
@first_prop_name: 
@Varargs: 


<!-- ##### FUNCTION gtk_container_get_resize_mode ##### -->
<para>

</para>

@container: 
@Returns: 


<!-- ##### FUNCTION gtk_container_set_resize_mode ##### -->
<para>

</para>

@container: 
@resize_mode: 


<!-- ##### FUNCTION gtk_container_check_resize ##### -->
<para>

</para>

@container: 


<!-- ##### FUNCTION gtk_container_foreach ##### -->
<para>

</para>

@container: 
@callback: 
@callback_data: 


<!-- ##### FUNCTION gtk_container_foreach_full ##### -->
<para>

</para>

@container: 
@callback: 
@marshal: 
@callback_data: 
@notify: 
@Deprecated: Use gtk_container_foreach() instead.


<!-- ##### MACRO gtk_container_children ##### -->
<para>
Does the same as gtk_container_get_children().
</para>

@Deprecated: Use gtk_container_get_children() instead.


<!-- ##### FUNCTION gtk_container_get_children ##### -->
<para>

</para>

@container: 
@Returns: 


<!-- ##### FUNCTION gtk_container_set_reallocate_redraws ##### -->
<para>

</para>

@container: 
@needs_redraws: 


<!-- ##### FUNCTION gtk_container_get_focus_child ##### -->
<para>

</para>

@container: 
@Returns: 


<!-- ##### FUNCTION gtk_container_set_focus_child ##### -->
<para>

</para>

@container: 
@child: 


<!-- ##### FUNCTION gtk_container_get_focus_vadjustment ##### -->
<para>

</para>

@container: 
@Returns: 


<!-- ##### FUNCTION gtk_container_set_focus_vadjustment ##### -->
<para>

</para>

@container: 
@adjustment: 


<!-- ##### FUNCTION gtk_container_get_focus_hadjustment ##### -->
<para>

</para>

@container: 
@Returns: 


<!-- ##### FUNCTION gtk_container_set_focus_hadjustment ##### -->
<para>

</para>

@container: 
@adjustment: 


<!-- ##### FUNCTION gtk_container_resize_children ##### -->
<para>

</para>

@container: 


<!-- ##### FUNCTION gtk_container_child_type ##### -->
<para>

</para>

@container: 
@Returns: 


<!-- ##### FUNCTION gtk_container_child_get ##### -->
<para>

</para>

@container: 
@child: 
@first_prop_name: 
@Varargs: 


<!-- ##### FUNCTION gtk_container_child_set ##### -->
<para>

</para>

@container: 
@child: 
@first_prop_name: 
@Varargs: 


<!-- ##### FUNCTION gtk_container_child_get_property ##### -->
<para>

</para>

@container: 
@child: 
@property_name: 
@value: 


<!-- ##### FUNCTION gtk_container_child_set_property ##### -->
<para>

</para>

@container: 
@child: 
@property_name: 
@value: 


<!-- ##### FUNCTION gtk_container_child_get_valist ##### -->
<para>

</para>

@container: 
@child: 
@first_property_name: 
@var_args: 


<!-- ##### FUNCTION gtk_container_child_set_valist ##### -->
<para>

</para>

@container: 
@child: 
@first_property_name: 
@var_args: 


<!-- ##### FUNCTION gtk_container_forall ##### -->
<para>

</para>

@container: 
@callback: 
@callback_data: 


<!-- ##### FUNCTION gtk_container_get_border_width ##### -->
<para>

</para>

@container: 
@Returns: 


<!-- ##### FUNCTION gtk_container_set_border_width ##### -->
<para>

</para>

@container: 
@border_width: 


<!-- ##### FUNCTION gtk_container_propagate_expose ##### -->
<para>

</para>

@container: 
@child: 
@event: 


<!-- ##### FUNCTION gtk_container_get_focus_chain ##### -->
<para>

</para>

@container: 
@focusable_widgets: 
@Returns: 


<!-- ##### FUNCTION gtk_container_set_focus_chain ##### -->
<para>

</para>

@container: 
@focusable_widgets: 


<!-- ##### FUNCTION gtk_container_unset_focus_chain ##### -->
<para>

</para>

@container: 


<!-- ##### FUNCTION gtk_container_class_find_child_property ##### -->
<para>

</para>

@cclass: 
@property_name: 
@Returns: 


<!-- ##### FUNCTION gtk_container_class_install_child_property ##### -->
<para>

</para>

@cclass: 
@property_id: 
@pspec: 


<!-- ##### FUNCTION gtk_container_class_list_child_properties ##### -->
<para>

</para>

@cclass: 
@n_properties: 
@Returns: