GtkOverlay

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

Synopsis

#include <gtk/gtk.h>

struct              GtkOverlay;
GtkWidget *         gtk_overlay_new                     (void);
void                gtk_overlay_add_overlay             (GtkOverlay *overlay,
                                                         GtkWidget *widget);

Object Hierarchy

  GObject
   +----GInitiallyUnowned
         +----GtkWidget
               +----GtkContainer
                     +----GtkBin
                           +----GtkOverlay

Implemented Interfaces

GtkOverlay implements AtkImplementorIface and GtkBuildable.

Signals

  "get-child-position"                             : Run Last

Description

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.

Details

struct GtkOverlay

struct GtkOverlay;

gtk_overlay_new ()

GtkWidget *         gtk_overlay_new                     (void);

Creates a new GtkOverlay.

Returns :

a new GtkOverlay object.

Since 3.2


gtk_overlay_add_overlay ()

void                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.

overlay :

a GtkOverlay

widget :

a GtkWidget to be added to the container

Since 3.2

Signal Details

The "get-child-position" signal

gboolean            user_function                      (GtkOverlay   *overlay,
                                                        GtkWidget    *widget,
                                                        GdkRectangle *allocation,
                                                        gpointer      user_data)       : Run Last

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

overlay :

the GtkOverlay

widget :

the child widget to position

allocation :

return location for the allocation. [out]

user_data :

user data set when the signal handler was connected.