Struct gtk::Container

source · [−]

#[repr(transparent)]
pub struct Container { /* private fields */ }

Expand description

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 Window containing a Frame containing a Label. If you wanted an image instead of a textual label inside the frame, you might replace the Label widget with a Image widget.

There are two major kinds of container widgets in GTK+. Both are subclasses of the abstract GtkContainer base class.

The first type of container widget has a single child widget and derives from Bin. These containers are decorators, which add some kind of functionality to the child. For example, a Button makes its child into a clickable button; a Frame draws a frame around its child and a Window places its child widget inside a top-level window.

The second type of container can have more than one child; its purpose is to manage layout. 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 Grid arranges the widgets it contains in a two-dimensional grid.

For implementations of Container the virtual method GtkContainerClass.forall() is always required, since it’s used for drawing and other internal operations on the children. If the Container implementation expect to have non internal children it’s needed to implement both GtkContainerClass.add() and GtkContainerClass.remove(). If the GtkContainer implementation has internal children, they should be added with WidgetExt::set_parent() on init() and removed with WidgetExt::unparent() in the GtkWidgetClass.destroy() implementation. See more about implementing custom widgets at https://wiki.gnome.org/HowDoI/CustomWidgets

Height for width geometry management

GTK+ uses a height-for-width (and width-for-height) geometry management system. Height-for-width means that a widget can change how much vertical space it needs, depending on the amount of horizontal space that it is given (and similar for width-for-height).

There are some things to keep in mind when implementing container widgets that make use of GTK+’s height for width geometry management system. First, it’s important to note that a container must prioritize one of its dimensions, that is to say that a widget or container can only have a SizeRequestMode that is SizeRequestMode::HeightForWidth or SizeRequestMode::WidthForHeight. However, every widget and container must be able to respond to the APIs for both dimensions, i.e. even if a widget has a request mode that is height-for-width, it is possible that its parent will request its sizes using the width-for-height APIs.

To ensure that everything works properly, here are some guidelines to follow when implementing height-for-width (or width-for-height) containers.

Each request mode involves 2 virtual methods. Height-for-width apis run through WidgetExt::preferred_width() and then through WidgetExt::preferred_height_for_width(). When handling requests in the opposite SizeRequestMode it is important that every widget request at least enough space to display all of its content at all times.

When WidgetExt::preferred_height() is called on a container that is height-for-width, the container must return the height for its minimum width. This is easily achieved by simply calling the reverse apis implemented for itself as follows:

⚠️ The following code is in C ⚠️

static void
foo_container_get_preferred_height (GtkWidget *widget,
                                    gint *min_height,
                                    gint *nat_height)
{
   if (i_am_in_height_for_width_mode)
     {
       gint min_width;

       GTK_WIDGET_GET_CLASS (widget)->get_preferred_width (widget,
                                                           &min_width,
                                                           NULL);
       GTK_WIDGET_GET_CLASS (widget)->get_preferred_height_for_width
                                                          (widget,
                                                           min_width,
                                                           min_height,
                                                           nat_height);
     }
   else
     {
       ... many containers support both request modes, execute the
       real width-for-height request here by returning the
       collective heights of all widgets that are stacked
       vertically (or whatever is appropriate for this container)
       ...
     }
}

Similarly, when WidgetExt::preferred_width_for_height() is called for a container or widget that is height-for-width, it then only needs to return the base minimum width like so:

⚠️ The following code is in C ⚠️

static void
foo_container_get_preferred_width_for_height (GtkWidget *widget,
                                              gint for_height,
                                              gint *min_width,
                                              gint *nat_width)
{
   if (i_am_in_height_for_width_mode)
     {
       GTK_WIDGET_GET_CLASS (widget)->get_preferred_width (widget,
                                                           min_width,
                                                           nat_width);
     }
   else
     {
       ... execute the real width-for-height request here based on
       the required width of the children collectively if the
       container were to be allocated the said height ...
     }
}

Height for width requests are generally implemented in terms of a virtual allocation of widgets in the input orientation. Assuming an height-for-width request mode, a container would implement the get_preferred_height_for_width() virtual function by first calling WidgetExt::preferred_width() for each of its children.

For each potential group of children that are lined up horizontally, the values returned by WidgetExt::preferred_width() should be collected in an array of GtkRequestedSize structures. Any child spacing should be removed from the input for_width and then the collective size should be allocated using the gtk_distribute_natural_allocation() convenience function.

The container will then move on to request the preferred height for each child by using WidgetExt::preferred_height_for_width() and using the sizes stored in the GtkRequestedSize array.

To allocate a height-for-width container, it’s again important to consider that a container must prioritize one dimension over the other. So if a container is a height-for-width container it must first allocate all widgets horizontally using a GtkRequestedSize array and gtk_distribute_natural_allocation() and then add any extra space (if and where appropriate) for the widget to expand.

After adding all the expand space, the container assumes it was allocated sufficient height to fit all of its content. At this time, the container must use the total horizontal sizes of each widget to request the height-for-width of each of its children and store the requests in a GtkRequestedSize array for any widgets that stack vertically (for tabular containers this can be generalized into the heights and widths of rows and columns). The vertical space must then again be distributed using gtk_distribute_natural_allocation() while this time considering the allocated height of the widget minus any vertical spacing that the container adds. Then vertical expand space should be added where appropriate and available and the container should go on to actually allocating the child widgets.

See [GtkWidget’s geometry management section][geometry-management] to learn more about implementing height-for-width geometry management for widgets.

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 Box.

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 ContainerExtManual::child_set_property(), gtk_container_child_set() or gtk_container_child_set_valist(). To obtain the value of a child property, use [ContainerExtManual::child_get_property()][crate::prelude::ContainerExtManual::child_get_property()], gtk_container_child_get() or gtk_container_child_get_valist(). To emit notification about child property changes, use WidgetExt::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.

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.

Since 3.16, containers can have a <focus-chain> element containing multiple <widget> elements, one for each child that should be added to the focus chain. The ”name” attribute gives the id of the widget.

An example of these properties in UI definitions:

⚠️ The following code is in xml ⚠️

<object class="GtkBox">
  <child>
    <object class="GtkEntry" id="entry1"/>
    <packing>
      <property name="pack-type">start</property>
    </packing>
  </child>
  <child>
    <object class="GtkEntry" id="entry2"/>
  </child>
  <focus-chain>
    <widget name="entry1"/>
    <widget name="entry2"/>
  </focus-chain>
</object>

This is an Abstract Base Class, you cannot instantiate it.

Implements

ContainerExt, WidgetExt, glib::ObjectExt, BuildableExt, ContainerExtManual, WidgetExtManual, BuildableExtManual

Struct gtk::Container

Implementations

impl Container

pub const NONE: Option<&'static Container> = None

Trait Implementations

impl Clone for Container

fn clone(&self) -> Self

fn clone_from(&mut self, source: &Self)

impl Debug for Container

fn fmt(&self, f: &mut Formatter<'_>) -> Result

impl Display for Container

fn fmt(&self, f: &mut Formatter<'_>) -> Result

impl Hash for Container

fn hash<H>(&self, state: &mut H) where H: Hasher,

fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher,

impl<T: ContainerImpl> IsSubclassable<T> for Container

fn class_init(class: &mut Class<Self>)

fn instance_init(instance: &mut InitializingObject<T>)

impl Ord for Container

fn cmp(&self, other: &Self) -> Ordering

fn max(self, other: Self) -> Self

fn min(self, other: Self) -> Self

fn clamp(self, min: Self, max: Self) -> Self

impl ParentClassIs for Container

type Parent = Widget

impl<OT: ObjectType> PartialEq<OT> for Container

fn eq(&self, other: &OT) -> bool

fn ne(&self, other: &Rhs) -> bool

impl<OT: ObjectType> PartialOrd<OT> for Container

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

fn lt(&self, other: &Rhs) -> bool

fn le(&self, other: &Rhs) -> bool

fn gt(&self, other: &Rhs) -> bool

fn ge(&self, other: &Rhs) -> bool

impl StaticType for Container

fn static_type() -> Type

impl Eq for Container

impl IsA<Buildable> for Container

impl IsA<Container> for AboutDialog

impl IsA<Container> for ActionBar

impl IsA<Container> for Button

impl IsA<Container> for ButtonBox

impl IsA<Container> for CheckButton

impl IsA<Container> for CheckMenuItem

impl IsA<Container> for ColorButton

impl IsA<Container> for ColorChooserDialog

impl IsA<Container> for ColorChooserWidget

impl IsA<Container> for ComboBox

impl IsA<Container> for ComboBoxText

impl IsA<Container> for Dialog

impl IsA<Container> for AppChooserButton

impl IsA<Container> for EventBox

impl IsA<Container> for Expander

impl IsA<Container> for FileChooserButton

impl IsA<Container> for FileChooserDialog

impl IsA<Container> for FileChooserWidget

impl IsA<Container> for Fixed

impl IsA<Container> for FlowBox

impl IsA<Container> for FlowBoxChild

impl IsA<Container> for FontButton

impl IsA<Container> for FontChooserDialog

impl IsA<Container> for AppChooserDialog

impl IsA<Container> for FontChooserWidget

impl IsA<Container> for Frame

impl IsA<Container> for Grid

impl IsA<Container> for HeaderBar

impl IsA<Container> for IconView

impl IsA<Container> for InfoBar

impl IsA<Container> for Layout

impl IsA<Container> for LinkButton

impl IsA<Container> for ListBox

impl IsA<Container> for ListBoxRow

impl IsA<Container> for AppChooserWidget

impl IsA<Container> for LockButton

impl IsA<Container> for Menu

impl IsA<Container> for MenuBar

impl IsA<Container> for MenuButton

impl IsA<Container> for MenuItem

impl IsA<Container> for MenuShell

impl IsA<Container> for MenuToolButton

fn hash<H>(&self, state: &mut H) where
H: Hasher,

fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,

impl<T> Any for T where
T: 'static + ?Sized,