Size Requisition

The size requisition of a widget is it's desired width and height. This is represented by a GtkRequisition.

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.

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.

Size Allocation

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.

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.

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.

Child properties

GtkContainer introduces child properties - 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.

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.

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().

GtkContainer as GtkBuildable

The GtkContainer implementation of the GtkBuildable interface supports a <packing> element for children, which can contain multiple <property> elements that specify child properties for the child.

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<object class="GtkVBox">
  <child>
    <object class="GtkLabel"/>
    <packing>
      <property name="pack-type">start</property>
    </packing>
  </child>
</object>

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.

GTK_IS_RESIZE_CONTAINER()

#define GTK_IS_RESIZE_CONTAINER(widget) (GTK_IS_CONTAINER (widget) && ((GtkContainer*) (widget))->resize_mode != GTK_RESIZE_PARENT)

GTK_CONTAINER_WARN_INVALID_CHILD_PROPERTY_ID()

#define             GTK_CONTAINER_WARN_INVALID_CHILD_PROPERTY_ID(object, property_id, pspec)

This macro should be used to emit a standard warning about unexpected properties in set_child_property() and get_child_property() implementations.

gtk_container_add ()

void
gtk_container_add (GtkContainer *container,
                   GtkWidget *widget);

Adds widget to container . Typically used for simple containers such as GtkWindow, GtkFrame, or GtkButton; for more complicated layout containers such as GtkBox or GtkTable, this function will pick default packing parameters that may not be correct. So consider functions such as gtk_box_pack_start() and gtk_table_attach() as an alternative to gtk_container_add() in those cases. A widget may be added to only one container at a time; you can't place the same widget inside two different containers.

gtk_container_remove ()

void
gtk_container_remove (GtkContainer *container,
                      GtkWidget *widget);

Removes widget from container . widget must be inside container . Note that container will own a reference to widget , and that this may be the last reference held; so removing a widget from its container can destroy that widget. If you want to use widget again, you need to add a reference to it while it's not inside a container, using g_object_ref(). If you don't want to use widget again it's usually more efficient to simply destroy it directly using gtk_widget_destroy() since this will remove it from the container and help break any circular reference count cycles.

gtk_container_add_with_properties ()

void
gtk_container_add_with_properties (GtkContainer *container,
                                   GtkWidget *widget,
                                   const gchar *first_prop_name,
                                   ...);

Adds widget to container , setting child properties at the same time. See gtk_container_add() and gtk_container_child_set() for more details.

gtk_container_get_resize_mode ()

GtkResizeMode
gtk_container_get_resize_mode (GtkContainer *container);

Returns the resize mode for the container. See gtk_container_set_resize_mode().

gtk_container_set_resize_mode ()

void
gtk_container_set_resize_mode (GtkContainer *container,
                               GtkResizeMode resize_mode);

Sets the resize mode for the container.

The resize mode of a container determines whether a resize request will be passed to the container's parent, queued for later execution or executed immediately.

gtk_container_check_resize ()

void
gtk_container_check_resize (GtkContainer *container);

gtk_container_foreach ()

void
gtk_container_foreach (GtkContainer *container,
                       GtkCallback callback,
                       gpointer callback_data);

Invokes callback on each non-internal child of container . See gtk_container_forall() for details on what constitutes an "internal" child. Most applications should use gtk_container_foreach(), rather than gtk_container_forall().

gtk_container_foreach_full ()

void
gtk_container_foreach_full (GtkContainer *container,
                            GtkCallback callback,
                            GtkCallbackMarshal marshal,
                            gpointer callback_data,
                            GDestroyNotify notify);

gtk_container_get_children ()

GList *
gtk_container_get_children (GtkContainer *container);

Returns the container's non-internal children. See gtk_container_forall() for details on what constitutes an "internal" child.

gtk_container_set_reallocate_redraws ()

void
gtk_container_set_reallocate_redraws (GtkContainer *container,
                                      gboolean needs_redraws);

Sets the reallocate_redraws flag of the container to the given value.

Containers requesting reallocation redraws get automatically redrawn if any of their children changed allocation.

gtk_container_get_focus_child ()

GtkWidget *
gtk_container_get_focus_child (GtkContainer *container);

Returns the current focus child widget inside container . This is not the currently focused widget. That can be obtained by calling gtk_window_get_focus().

Since: 2.14

gtk_container_set_focus_child ()

void
gtk_container_set_focus_child (GtkContainer *container,
                               GtkWidget *child);

Sets, or unsets if child is NULL, the focused child of container .

This function emits the GtkContainer::set_focus_child signal of container . Implementations of GtkContainer can override the default behaviour by overriding the class closure of this signal.

This is function is mostly meant to be used by widgets. Applications can use gtk_widget_grab_focus() to manualy set the focus to a specific widget.

gtk_container_get_focus_vadjustment ()

GtkAdjustment *
gtk_container_get_focus_vadjustment (GtkContainer *container);

Retrieves the vertical focus adjustment for the container. See gtk_container_set_focus_vadjustment().

gtk_container_set_focus_vadjustment ()

void
gtk_container_set_focus_vadjustment (GtkContainer *container,
                                     GtkAdjustment *adjustment);

Hooks up an adjustment to focus handling in a container, so when a child of the container is focused, the adjustment is scrolled to show that widget. This function sets the vertical alignment. See gtk_scrolled_window_get_vadjustment() for a typical way of obtaining the adjustment and gtk_container_set_focus_hadjustment() for setting the horizontal adjustment.

The adjustments have to be in pixel units and in the same coordinate system as the allocation for immediate children of the container.

gtk_container_get_focus_hadjustment ()

GtkAdjustment *
gtk_container_get_focus_hadjustment (GtkContainer *container);

Retrieves the horizontal focus adjustment for the container. See gtk_container_set_focus_hadjustment().

gtk_container_set_focus_hadjustment ()

void
gtk_container_set_focus_hadjustment (GtkContainer *container,
                                     GtkAdjustment *adjustment);

Hooks up an adjustment to focus handling in a container, so when a child of the container is focused, the adjustment is scrolled to show that widget. This function sets the horizontal alignment. See gtk_scrolled_window_get_hadjustment() for a typical way of obtaining the adjustment and gtk_container_set_focus_vadjustment() for setting the vertical adjustment.

The adjustments have to be in pixel units and in the same coordinate system as the allocation for immediate children of the container.

gtk_container_resize_children ()

void
gtk_container_resize_children (GtkContainer *container);

gtk_container_child_type ()

GType
gtk_container_child_type (GtkContainer *container);

Returns the type of the children supported by the container.

Note that this may return G_TYPE_NONE to indicate that no more children can be added, e.g. for a GtkPaned which already has two children.

gtk_container_child_get ()

void
gtk_container_child_get (GtkContainer *container,
                         GtkWidget *child,
                         const gchar *first_prop_name,
                         ...);

Gets the values of one or more child properties for child and container .

gtk_container_child_set ()

void
gtk_container_child_set (GtkContainer *container,
                         GtkWidget *child,
                         const gchar *first_prop_name,
                         ...);

Sets one or more child properties for child and container .

gtk_container_child_get_property ()

void
gtk_container_child_get_property (GtkContainer *container,
                                  GtkWidget *child,
                                  const gchar *property_name,
                                  GValue *value);

Gets the value of a child property for child and container .

gtk_container_child_set_property ()

void
gtk_container_child_set_property (GtkContainer *container,
                                  GtkWidget *child,
                                  const gchar *property_name,
                                  const GValue *value);

Sets a child property for child and container .

gtk_container_child_get_valist ()

void
gtk_container_child_get_valist (GtkContainer *container,
                                GtkWidget *child,
                                const gchar *first_property_name,
                                va_list var_args);

Gets the values of one or more child properties for child and container .

gtk_container_child_set_valist ()

void
gtk_container_child_set_valist (GtkContainer *container,
                                GtkWidget *child,
                                const gchar *first_property_name,
                                va_list var_args);

Sets one or more child properties for child and container .

gtk_container_forall ()

void
gtk_container_forall (GtkContainer *container,
                      GtkCallback callback,
                      gpointer callback_data);

Invokes callback on each child of container , including children that are considered "internal" (implementation details of the container). "Internal" children generally weren't added by the user of the container, but were added by the container implementation itself. Most applications should use gtk_container_foreach(), rather than gtk_container_forall().

gtk_container_get_border_width ()

guint
gtk_container_get_border_width (GtkContainer *container);

Retrieves the border width of the container. See gtk_container_set_border_width().

gtk_container_set_border_width ()

void
gtk_container_set_border_width (GtkContainer *container,
                                guint border_width);

Sets the border width of the container.

The border width of a container is the amount of space to leave around the outside of the container. The only exception to this is GtkWindow; because toplevel windows can't leave space outside, they leave the space inside. The border is added on all sides of the container. To add space to only one side, one approach is to create a GtkAlignment widget, call gtk_widget_set_size_request() to give it a size, and place it on the side of the container as a spacer.

gtk_container_propagate_expose ()

void
gtk_container_propagate_expose (GtkContainer *container,
                                GtkWidget *child,
                                GdkEventExpose *event);

When a container receives an expose event, it must send synthetic expose events to all children that don't have their own GdkWindows. This function provides a convenient way of doing this. A container, when it receives an expose event, calls gtk_container_propagate_expose() once for each child, passing in the event the container received.

gtk_container_propagate_expose() takes care of deciding whether an expose event needs to be sent to the child, intersecting the event's area with the child area, and sending the event.

In most cases, a container can simply either simply inherit the “expose” implementation from GtkContainer, or, do some drawing and then chain to the ::expose implementation from GtkContainer.

Note that the ::expose-event signal has been replaced by a ::draw signal in GTK+ 3, and consequently, gtk_container_propagate_expose() has been replaced by gtk_container_propagate_draw(). The GTK+ 3 migration guide for hints on how to port from ::expose-event to ::draw.

gtk_container_get_focus_chain ()

gboolean
gtk_container_get_focus_chain (GtkContainer *container,
                               GList **focusable_widgets);

Retrieves the focus chain of the container, if one has been set explicitly. If no focus chain has been explicitly set, GTK+ computes the focus chain based on the positions of the children. In that case, GTK+ stores NULL in focusable_widgets and returns FALSE.

gtk_container_set_focus_chain ()

void
gtk_container_set_focus_chain (GtkContainer *container,
                               GList *focusable_widgets);

Sets a focus chain, overriding the one computed automatically by GTK+.

In principle each widget in the chain should be a descendant of the container, but this is not enforced by this method, since it's allowed to set the focus chain before you pack the widgets, or have a widget in the chain that isn't always packed. The necessary checks are done when the focus chain is actually traversed.

gtk_container_unset_focus_chain ()

void
gtk_container_unset_focus_chain (GtkContainer *container);

Removes a focus chain explicitly set with gtk_container_set_focus_chain().

gtk_container_class_find_child_property ()

GParamSpec *
gtk_container_class_find_child_property
                               (GObjectClass *cclass,
                                const gchar *property_name);

Finds a child property of a container class by name.

gtk_container_class_install_child_property ()

void
gtk_container_class_install_child_property
                               (GtkContainerClass *cclass,
                                guint property_id,
                                GParamSpec *pspec);

Installs a child property on a container class.

gtk_container_class_list_child_properties ()

GParamSpec **
gtk_container_class_list_child_properties
                               (GObjectClass *cclass,
                                guint *n_properties);

Returns all child properties of a container class.

struct GtkContainer

struct GtkContainer;

gtk_container_border_width

#define gtk_container_border_width		gtk_container_set_border_width

Does the same as gtk_container_set_border_width().

gtk_container_children

#define gtk_container_children gtk_container_get_children

Does the same as gtk_container_get_children().

The “border-width” property

  “border-width”             guint

The width of the empty border outside the containers children.

Flags: Read / Write

Allowed values: <= 65535

Default value: 0

The “child” property

  “child”                    GtkWidget *

Can be used to add a new child to the container.

Flags: Write

The “resize-mode” property

  “resize-mode”              GtkResizeMode

Specify how resize events are handled.

Flags: Read / Write

Default value: GTK_RESIZE_PARENT

The “add” signal

void
user_function (GtkContainer *container,
               GtkWidget    *widget,
               gpointer      user_data)

Flags: Run First

The “check-resize” signal

void
user_function (GtkContainer *container,
               gpointer      user_data)

Flags: Run Last

The “remove” signal

void
user_function (GtkContainer *container,
               GtkWidget    *widget,
               gpointer      user_data)

Flags: Run First

The “set-focus-child” signal

void
user_function (GtkContainer *container,
               GtkWidget    *widget,
               gpointer      user_data)

Flags: Run First