Size Requisition

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

How a widget determines its desired size depends on the widget. A gtk.Label, 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 the gtk.Window.set_resizable() method), 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 the size_allocate() method. 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 gtk.Window will always give its child the amount of space the child requested.

A child's size allocation is represented by a gtk.gdk.Rectangle that 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 is available, 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

gtk.Container 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 gtk.Box.

Use the install_child_property() method to install child properties for a container class and the list_child_properties() function to get information about existing child properties.

To set the value of a child property, use the child_set_property(), or child_set() methods. To obtain the value of a child property, use the child_get_property(), or child_get() methods. To emit notification about child property changes, use the gtk.Widget.child_notify() method.

gtk.Container.set_border_width

    def set_border_width(border_width)

The set_border_width() method sets the "border-width" property 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 gtk.Window; because toplevel windows can't leave space outside, they leave the space inside. The border is added on all sides of the container.

gtk.Container.get_border_width

    def get_border_width()

The get_border_width() method retrieves the value of the "border-width" property of the container. See set_border_width().

gtk.Container.add

    def add(widget)

The add() method adds widget to the container. This method is typically used for simple containers such as gtk.Window, gtk.Frame, or gtk.Button that hold a single child widget. For layout containers that handle multiple children such as gtk.Box or gtk.Table, this function will pick default packing parameters that may not be correct. Containers that handle multiple children usually have additional methods such as gtk.Box.pack_start() and gtk.Table.attach() as an alternative to add(). Adding a widget to a container usually results in the resizing and redrawing of the container contents.

gtk.Container.remove

    def remove(widget)

The remove() method removes widget from the container. widget must be inside the container. Note that the container will own a reference to widget, and that this may be the last reference held; so removing a widget from its container can cause that widget to be destroyed. If you want to use widget again, you should add a reference to it.

gtk.Container.set_resize_mode

    def set_resize_mode(resize_mode)

The set-resize_mode() method sets the "resize=mode" property of the container. The resize mode of a container determines whether a resize request will be passed to the container's parent (gtk.RESIZE_PARENT), queued for later execution (gtk.RESIZE_QUEUE) or executed immediately (gtk.RESIZE_IMMEDIATE).

gtk.Container.get_resize_mode

    def get_resize_mode()

The get_resize_mode() method returns the value of the "resize-mode" property for of the container. See set_resize_mode().

gtk.Container.check_resize

    def check_resize()

The check_resize() method emits the "check-resize" signal on the container.

gtk.Container.forall

    def forall(callback, callback_data=None)

The forall() method arranges to invoke callback on each child of the 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 the foreach() method, rather than the forall() method.

gtk.Container.foreach

    def foreach(callback, callback_data=None)

The foreach() method arranges to invoke callback on each non-internal child of the container.

gtk.Container.get_children

    def get_children()

The get_children() method returns the container's non-internal children.

gtk.Container.propagate_expose

    def propagate_expose(child, event)

The propagate_expose() method sends synthetic expose events to all children that don't have their own gtk.gdk.Windows when the container receives an expose event.

The 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 gtk.Container, or, do some drawing and then chain to the expose implementation from gtk.Container.

gtk.Container.set_focus_chain

    def set_focus_chain(focusable_widgets)

The set_focus_chain() method 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.get_focus_chain

    def get_focus_chain()

The get_focus_chain() method 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, the method returns None.

gtk.Container.unset_focus_chain

    def unset_focus_chain()

The unset_focus_chain() method removes a focus chain explicitly set with set_focus_chain().

gtk.Container.set_reallocate_redraws

    def set_reallocate_redraws(needs_redraws)

The set_reallocate_redraws() method sets the reallocate_redraws attribute of the container to the value of needs_redraws. Containers requesting reallocation redraws get automatically redrawn if any of their children change allocation.

gtk.Container.set_focus_child

    def set_focus_child(child)

The set_focus_child() method emits the "set-focus-child" signal that arranges for the child widget referenced by child to get the focus and recalculates the container adjustments.

gtk.Container.get_focus_child

    def get_focus_child()

The get_focus_child() method returns the current focus child widget inside container.

gtk.Container.set_focus_vadjustment

    def set_focus_vadjustment(adjustment)

The set_focus_vadjustment() method sets the vertical focus adjustment to the value of adjustment.

gtk.Container.get_focus_vadjustment

    def get_focus_vadjustment()

The get_focus_vadjustment() method retrieves the vertical focus adjustment for the container. See the set_focus_vadjustment() method.

gtk.Container.set_focus_hadjustment

    def set_focus_hadjustment(adjustment)

The set_focus_hadjustment() method sets the horizontal focus adjustment to the value of adjustment.

gtk.Container.get_focus_hadjustment

    def get_focus_hadjustment()

The get_focus_hadjustment() method retrieves the horizontal focus adjustment for the container. See set_focus_hadjustment().

gtk.Container.resize_children

    def resize_children()

The resize_children() method causes the container to recalculate its size and its children's sizes.

gtk.Container.child_type

    def child_type()

The child_type() method returns the type of the children that can be added to the container. Note that this may return a void type to indicate that no more children can be added, e.g. for a gtk.Paned which already has two children or a gtk.Window that already has a child.

gtk.Container.add_with_properties

    def add_with_properties(widget, first_prop_name, first_prop_value, ...)

The add_with_properties() method adds the child widget specified by widget to the container while allowing the setting of zero or more container child property values at the same time. Containers supporting add with settable child properties are: gtk.Box, gtk.Fixed, gtk.Notebook and gtk.Table.

For example the following adds a button to a gtk.Fixed layout widget and sets the child properties "x" and "y" specifying the child position in the layout:

  fixed.add_with_properties(button, "x", 10, "y", 20")

gtk.Container.child_set

    def child_set(child, first_prop_name, ...)

The child_set() method sets the properties for child using the given property name and value pairs.

gtk.Container.child_get

    def child_get(child, first_prop_name, ...)

The child_get() method retrieves the requested container child properties for child.

gtk.Container.child_set_property

    def child_set_property(child, property_name, value)

The child_set_property() method sets the property name specified by property_name with the value specified in value.

gtk.Container.child_get_property

    def child_get_property(child, property_name)

The child_get_property() method retrieves the value of the child property specified by property_name for the widget child.

gtk.Container.install_child_property

    def install_child_property(property_id, pspec)

The install_child_property() method installs a child property for the container class using the integer ID specified by property_id. pspec is a tuple containing at least 5 items. The first 4 items contain the following parameter specification items:

The last item must be a integer containing a combination of the GObject Param Flag Constants. Additional tuple items (if needed) are inserted between the fourth item and the last item depending on the property type:

gtk.Container.list_child_properties

    def list_child_properties()

The list_child_properties() method returns a list containing the child properties of the container class. See the install_child_property() method for more information.

gtk.container_class_install_child_property

    def gtk.container_class_install_child_property(klass, property_id, pspec)

The gtk.container_class_install_child_property() function installs a child property for the container class specified by klass using the integer ID specified by property_id. pspec is a tuple containing at least 5 items. The first 4 items contain the following parameter specification items:

The last item must be a integer containing a combination of the GObject Param Flag Constants. Additional tuple items (if needed) are inserted between the fourth item and the last item depending on the property type:

gtk.container_class_list_child_properties

    def gtk.container_class_list_child_properties(klass)

The gtk.container_class_list_child_properties() function returns a tuple containing the child properties of the container class specified by klass.

The "add" gtk.Container Signal

    def callback(container, widget, user_param1, ...)

The "add" signal is emitted when widget is added to the container.

The "check-resize" gtk.Container Signal

    def callback(container, user_param1, ...)

The "check-resize" signal is emitted when the check_resize() method is called forcing the recalculation of the container and its children. See the set_resize_mode() method for details.

The "remove" gtk.Container Signal

    def callback(container, widget, user_param1, ...)

The "remove" signal is emitted when widget is removed from container.

The "set-focus-child" gtk.Container Signal

    def callback(container, widget, user_param1, ...)

The "set-focus-child" signal is emitted when the set_focus_child() method is called. widget is set as the child in container with the focus.