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GtkOverlay — A container which overlays widgets on top of each other


Types and Values

struct GtkOverlay
struct GtkOverlayClass

Object Hierarchy

    ╰── GInitiallyUnowned
        ╰── GtkWidget
            ╰── GtkContainer
                ╰── GtkBin
                    ╰── GtkOverlay

Implemented Interfaces

GtkOverlay implements AtkImplementorIface and GtkBuildable.


#include <gtk/gtk.h>


GtkOverlay is a container which contains a single main child, on top of which it can place “overlay” widgets. The position of each overlay widget is determined by its “halign” and “valign” properties. E.g. a widget with both alignments set to GTK_ALIGN_START will be placed at the top left corner of the main widget, whereas an overlay with halign set to GTK_ALIGN_CENTER and valign set to GTK_ALIGN_END will be placed a the bottom edge of the main widget, horizontally centered. The position can be adjusted by setting the margin properties of the child to non-zero values.

More complicated placement of overlays is possible by connecting to the “get-child-position” signal.

GtkOverlay as GtkBuildable

The GtkOverlay implementation of the GtkBuildable interface supports placing a child as an overlay by specifying “overlay” as the “type” attribute of a <child> element.


gtk_overlay_new ()

GtkWidget *
gtk_overlay_new (void);

Creates a new GtkOverlay.


a new GtkOverlay object.

Since 3.2

gtk_overlay_add_overlay ()

gtk_overlay_add_overlay (GtkOverlay *overlay,
                         GtkWidget *widget);

Adds widget to overlay .

The widget will be stacked on top of the main widget added with gtk_container_add().

The position at which widget is placed is determined from its “halign” and “valign” properties.



a GtkOverlay



a GtkWidget to be added to the container


Since 3.2

Types and Values

struct GtkOverlay

struct GtkOverlay;

struct GtkOverlayClass

struct GtkOverlayClass {
  GtkBinClass parent_class;

  gboolean (*get_child_position) (GtkOverlay    *overlay,
                                  GtkWidget     *widget,
                                  GtkAllocation *allocation);


GtkBinClass parent_class;

The parent class.


get_child_position ()

Signal emitted to determine the position and size of any overlay child widgets.


Signal Details

The “get-child-position” signal

user_function (GtkOverlay   *overlay,
               GtkWidget    *widget,
               GdkRectangle *allocation,
               gpointer      user_data)

The ::get-child-position signal is emitted to determine the position and size of any overlay child widgets. A handler for this signal should fill allocation with the desired position and size for widget , relative to the 'main' child of overlay .

The default handler for this signal uses the widget 's halign and valign properties to determine the position and gives the widget its natural size (except that an alignment of GTK_ALIGN_FILL will cause the overlay to be full-width/height). If the main child is a GtkScrolledWindow, the overlays are placed relative to its contents.

Return: TRUE if the allocation has been filled



the GtkOverlay



the child widget to position



return location for the allocation.

[out caller-allocates]


user data set when the signal handler was connected.


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