GtkLayoutManager

GtkLayoutManager — Base class for layout manager

Types and Values

Object Hierarchy

    GObject
    ╰── GtkLayoutManager
        ├── GtkBinLayout
        ├── GtkBoxLayout
        ├── GtkCenterLayout
        ├── GtkConstraintLayout
        ├── GtkFixedLayout
        ├── GtkGridLayout
        ╰── GtkOverlayLayout

Includes

#include <gtk/gtk.h>

Description

Layout managers are delegate classes that handle the preferred size and the allocation of a container widget.

You typically subclass GtkLayoutManager if you want to implement a layout policy for the children of a widget, or if you want to determine the size of a widget depending on its contents.

Each GtkWidget can only have a GtkLayoutManager instance associated to it at any given time; it is possible, though, to replace the layout manager instance using gtk_widget_set_layout_manager().

Layout properties

A layout manager can expose properties for controlling the layout of each child, by creating an object type derived from GtkLayoutChild and installing the properties on it as normal GObject properties.

Each GtkLayoutChild instance storing the layout properties for a specific child is created through the gtk_layout_manager_get_layout_child() method; a GtkLayoutManager controls the creation of its GtkLayoutChild instances by overriding the GtkLayoutManagerClass.create_layout_child() virtual function. The typical implementation should look like:

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static GtkLayoutChild *
create_layout_child (GtkLayoutManager *manager,
                     GtkWidget        *container,
                     GtkWidget        *child)
{
  return g_object_new (your_layout_child_get_type (),
                       "layout-manager", manager,
                       "child-widget", child,
                       NULL);
}

The “layout-manager” and “child-widget” properties on the newly created GtkLayoutChild instance are mandatory. The GtkLayoutManager will cache the newly created GtkLayoutChild instance until the widget is removed from its parent, or the parent removes the layout manager.

Each GtkLayoutManager instance creating a GtkLayoutChild should use gtk_layout_manager_get_layout_child() every time it needs to query the layout properties; each GtkLayoutChild instance should call gtk_layout_manager_layout_changed() every time a property is updated, in order to queue a new size measuring and allocation.

Functions

gtk_layout_manager_measure ()

void
gtk_layout_manager_measure (GtkLayoutManager *manager,
                            GtkWidget *widget,
                            GtkOrientation orientation,
                            int for_size,
                            int *minimum,
                            int *natural,
                            int *minimum_baseline,
                            int *natural_baseline);

Measures the size of the widget using manager , for the given orientation and size.

See GtkWidget's geometry management section for more details.

Parameters

manager

a GtkLayoutManager

 

widget

the GtkWidget using manager

 

orientation

the orientation to measure

 

for_size

Size for the opposite of orientation ; for instance, if the orientation is GTK_ORIENTATION_HORIZONTAL, this is the height of the widget; if the orientation is GTK_ORIENTATION_VERTICAL, this is the width of the widget. This allows to measure the height for the given width, and the width for the given height. Use -1 if the size is not known

 

minimum

the minimum size for the given size and orientation.

[out][optional]

natural

the natural, or preferred size for the given size and orientation.

[out][optional]

minimum_baseline

the baseline position for the minimum size.

[out][optional]

natural_baseline

the baseline position for the natural size.

[out][optional]

gtk_layout_manager_allocate ()

void
gtk_layout_manager_allocate (GtkLayoutManager *manager,
                             GtkWidget *widget,
                             int width,
                             int height,
                             int baseline);

This function assigns the given width , height , and baseline to a widget , and computes the position and sizes of the children of the widget using the layout management policy of manager .

Parameters

manager

a GtkLayoutManager

 

widget

the GtkWidget using manager

 

width

the new width of the widget

 

height

the new height of the widget

 

baseline

the baseline position of the widget , or -1

 

gtk_layout_manager_get_request_mode ()

GtkSizeRequestMode
gtk_layout_manager_get_request_mode (GtkLayoutManager *manager);

Retrieves the request mode of manager .

Parameters

manager

a GtkLayoutManager

 

Returns

a GtkSizeRequestMode


gtk_layout_manager_get_widget ()

GtkWidget *
gtk_layout_manager_get_widget (GtkLayoutManager *manager);

Retrieves the GtkWidget using the given GtkLayoutManager.

Parameters

manager

a GtkLayoutManager

 

Returns

a GtkWidget.

[transfer none][nullable]


gtk_layout_manager_get_layout_child ()

GtkLayoutChild *
gtk_layout_manager_get_layout_child (GtkLayoutManager *manager,
                                     GtkWidget *child);

Retrieves a GtkLayoutChild instance for the GtkLayoutManager, creating one if necessary.

The child widget must be a child of the widget using manager .

The GtkLayoutChild instance is owned by the GtkLayoutManager, and is guaranteed to exist as long as child is a child of the GtkWidget using the given GtkLayoutManager.

Parameters

manager

a GtkLayoutManager

 

child

a GtkWidget

 

Returns

a GtkLayoutChild.

[transfer none]


gtk_layout_manager_layout_changed ()

void
gtk_layout_manager_layout_changed (GtkLayoutManager *manager);

Queues a resize on the GtkWidget using manager , if any.

This function should be called by subclasses of GtkLayoutManager in response to changes to their layout management policies.

Parameters

manager

a GtkLayoutManager

 

Types and Values

GtkLayoutManager

typedef struct _GtkLayoutManager GtkLayoutManager;

struct GtkLayoutManagerClass

struct GtkLayoutManagerClass {
  GtkSizeRequestMode (* get_request_mode)    (GtkLayoutManager *manager,
                                              GtkWidget        *widget);

  void               (* measure)             (GtkLayoutManager *manager,
                                              GtkWidget        *widget,
                                              GtkOrientation    orientation,
                                              int               for_size,
                                              int              *minimum,
                                              int              *natural,
                                              int              *minimum_baseline,
                                              int              *natural_baseline);

  void               (* allocate)            (GtkLayoutManager *manager,
                                              GtkWidget        *widget,
                                              int               width,
                                              int               height,
                                              int               baseline);

  GType              layout_child_type;

  GtkLayoutChild *   (* create_layout_child) (GtkLayoutManager *manager,
                                              GtkWidget        *widget,
                                              GtkWidget        *for_child);

  void               (* root)                (GtkLayoutManager *manager);
  void               (* unroot)              (GtkLayoutManager *manager);
};

The GtkLayoutManagerClass structure contains only private data, and should only be accessed through the provided API, or when subclassing GtkLayoutManager.

Members

get_request_mode ()

a virtual function, used to return the preferred request mode for the layout manager; for instance, "width for height" or "height for width"; see GtkSizeRequestMode

 

measure ()

a virtual function, used to measure the minimum and preferred sizes of the widget using the layout manager for a given orientation

 

allocate ()

a virtual function, used to allocate the size of the widget using the layout manager

 

GType layout_child_type;

the type of GtkLayoutChild used by this layout manager

 

create_layout_child ()

a virtual function, used to create a GtkLayoutChild meta object for the layout properties

 

root ()

a virtual function, called when the widget using the layout manager is attached to a GtkRoot

 

unroot ()

a virtual function, called when the widget using the layout manager is detached from a GtkRoot