GtkOverlay

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

Functions

GtkWidget * gtk_overlay_new ()
void gtk_overlay_add_overlay ()
void gtk_overlay_reorder_overlay ()
gboolean gtk_overlay_get_overlay_pass_through ()
void gtk_overlay_set_overlay_pass_through ()

Child Properties

gint index Read / Write
gboolean pass-through Read / Write

Signals

gboolean get-child-position Run Last

Types and Values

struct GtkOverlay
struct GtkOverlayClass

Object Hierarchy

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

Implemented Interfaces

GtkOverlay implements AtkImplementorIface and GtkBuildable.

Includes

#include <gtk/gtk.h>

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 GtkOverlay container, 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 GtkOverlay, 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.

Functions

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.

Parameters

overlay

a GtkOverlay

widget

a GtkWidget to be added to the container

Since: 3.2

gtk_overlay_reorder_overlay ()

void
gtk_overlay_reorder_overlay (GtkOverlay *overlay,
                             GtkWidget *child,
                             gint position);

Moves child to a new index in the list of overlay children. The list contains overlays in the order that these were added to overlay .

A widget’s index in the overlay children list determines which order the children are drawn if they overlap. The first child is drawn at the bottom. It also affects the default focus chain order.

Parameters

overlay

a GtkOverlay

child

the overlaid GtkWidget to move

position

the new index for child in the list of overlay children of overlay , starting from 0. If negative, indicates the end of the list

gtk_overlay_get_overlay_pass_through ()

gboolean
gtk_overlay_get_overlay_pass_through (GtkOverlay *overlay,
                                      GtkWidget *widget);

Convenience function to get the value of the “pass-through” child property for widget .

Parameters

overlay

a GtkOverlay

widget

an overlay child of GtkOverlay

Returns

whether the widget is a pass through child.

Since: 3.18

gtk_overlay_set_overlay_pass_through ()

void
gtk_overlay_set_overlay_pass_through (GtkOverlay *overlay,
                                      GtkWidget *widget,
                                      gboolean pass_through);

Convenience function to set the value of the “pass-through” child property for widget .

Parameters

overlay

a GtkOverlay

widget

an overlay child of GtkOverlay

pass_through

whether the child should pass the input through

Since: 3.18

Types and Values

struct GtkOverlay

struct GtkOverlay;

struct GtkOverlayClass

struct GtkOverlayClass {
  GtkBinClass parent_class;


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

Members

get_child_position ()

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

Child Property Details

The “index” child property

  “index”                    gint

The index of the overlay in the parent, -1 for the main child.

Flags: Read / Write

Allowed values: >= -1

Default value: 0

The “pass-through” child property

  “pass-through”             gboolean

Pass through input, does not affect main child.

Flags: Read / Write

Default value: FALSE

Signal Details

The “get-child-position” signal

gboolean
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.

Parameters

overlay

the GtkOverlay

widget

the child widget to position

allocation

return location for the allocation.

[type Gdk.Rectangle][out caller-allocates]

user_data

user data set when the signal handler was connected.

Returns

TRUE if the allocation has been filled

Flags: Run Last

© 2005–2020 The GNOME Project
Licensed under the GNU Lesser General Public License version 2.1 or later.
https://developer.gnome.org/gtk3/3.20/GtkOverlay.html