<!-- ##### SECTION Title ##### -->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 innernodes 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 containersare <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 itcontains 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 callinggtk_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 thesize 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 spacethe 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 muchspace 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 widgetsmust 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 specificto 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 widgetwhich 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() orgtk_container_class_list_child_properties() to get information about existingchild 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() orgtk_container_child_get_valist(). To emit notification about child property changes, use gtk_widget_child_notify().</para></refsect2><!-- ##### SECTION See_Also ##### --><para></para><!-- ##### SECTION Stability_Level ##### --><!-- ##### 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></para>@object: @property_id: @pspec: <!-- ##### 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>@Returns: @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_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: <!-- # Unused Parameters # -->@first_arg_name: <!-- ##### 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: <!-- # Unused Parameters # -->@class: <!-- ##### FUNCTION gtk_container_class_install_child_property ##### --><para></para>@cclass: @property_id: @pspec: <!-- # Unused Parameters # -->@class: <!-- ##### FUNCTION gtk_container_class_list_child_properties ##### --><para></para>@cclass: @n_properties: @Returns: <!-- # Unused Parameters # -->@class: