class Gtk::SizeGroup

Overview

Groups widgets together so they all request the same size.

This is typically useful when you want a column of widgets to have the same size, but you can’t use a Gtk::Grid or Gtk::Box.

In detail, the size requested for each widget in a Gtk::SizeGroup is the maximum of the sizes that would have been requested for each widget in the size group if they were not in the size group. The [mode]Gtk::SizeGroup#mode= of the size group determines whether this applies to the horizontal size, the vertical size, or both sizes.

Note that size groups only affect the amount of space requested, not the size that the widgets finally receive. If you want the widgets in a Gtk::SizeGroup to actually be the same size, you need to pack them in such a way that they get the size they request and not more. In particular it doesn't make a lot of sense to set [the expand flags]Gtk::Widget#hexpand= on the widgets that are members of a size group.

Gtk::SizeGroup objects are referenced by each widget in the size group, so once you have added all widgets to a Gtk::SizeGroup, you can drop the initial reference to the size group with GObject::Object#unref. If the widgets in the size group are subsequently destroyed, then they will be removed from the size group and drop their references on the size group; when all widgets have been removed, the size group will be freed.

Widgets can be part of multiple size groups; GTK will compute the horizontal size of a widget from the horizontal requisition of all widgets that can be reached from the widget by a chain of size groups with mode Gtk::SizeGroupMode#HORIZONTAL or Gtk::SizeGroupMode#BOTH, and the vertical size from the vertical requisition of all widgets that can be reached from the widget by a chain of size groups with mode Gtk::SizeGroupMode#VERTICAL or Gtk::SizeGroupMode#BOTH.

Size groups and trading height-for-width

::: warning Generally, size groups don't interact well with widgets that trade height for width (or width for height), such as wrappable labels. Avoid using size groups with such widgets.

A size group with mode Gtk::SizeGroupMode#HORIZONTAL or Gtk::SizeGroupMode#VERTICAL only consults non-contextual sizes of widgets other than the one being measured, since it has no knowledge of what size a widget will get allocated in the other orientation. This can lead to widgets in a group actually requesting different contextual sizes, contrary to the purpose of Gtk::SizeGroup.

In contrast, a size group with mode Gtk::SizeGroupMode#BOTH can properly propagate the available size in the opposite orientation when measuring widgets in the group, which results in consistent and accurate measurements.

In case some mechanism other than a size group is already used to ensure that widgets in a group all get the same size in one orientation (for example, some common ancestor is known to allocate the same width to all its children), and the size group is only really needed to also make the widgets request the same size in the other orientation, it is beneficial to still set the group's mode to Gtk::SizeGroupMode#BOTH. This lets the group assume and count on sizes of the widgets in the former orientation being the same, which enables it to propagate the available size as described above.

Alternatives to size groups

Size groups have many limitations, such as only influencing size requests but not allocations, and poor height-for-width support. When possible, prefer using dedicated mechanisms that can properly ensure that the widgets get the same size.

Various container widgets and layout managers support a homogeneous layout mode, where they will explicitly give the same size to their children (see Gtk::Box#homogeneous). Using homogeneous mode can also have large performance benefits compared to either the same container in non-homogeneous mode, or to size groups.

Gtk::Grid can be used to position widgets into rows and columns. Members of each column will have the same width among them; likewise, members of each row will have the same height. On top of that, the heights can be made equal between all rows with [property@Gtk.Grid:row-homogeneous], and the widths can be made equal between all columns with [property@Gtk.Grid:column-homogeneous].

Gtk::SizeGroup as Gtk::Buildable

Size groups can be specified in a UI definition by placing an <object> element with class="Gtk::SizeGroup" somewhere in the UI definition. The widgets that belong to the size group are specified by a <widgets> element that may contain multiple <widget> elements, one for each member of the size group. The ”name” attribute gives the id of the widget.

An example of a UI definition fragment with Gtk::SizeGroup:

WARNING ⚠️ The following code is in xml ⚠️

<object class="Gtk::SizeGroup">
  <property name="mode">horizontal</property>
  <widgets>
    <widget name="radio1"/>
    <widget name="radio2"/>
  </widgets>
</object>

Included Modules

Defined in:

lib/gi-crystal/src/auto/gtk-4.0/size_group.cr

Constructors

Class Method Summary

Instance Method Summary

Instance methods inherited from module Gtk::Buildable

buildable_id : String | Nil buildable_id, to_unsafe to_unsafe

Constructor methods inherited from module Gtk::Buildable

cast(obj : GObject::Object) : self cast

Class methods inherited from module Gtk::Buildable

cast?(obj : GObject::Object) : self | Nil cast?, g_type : UInt64 g_type

Instance methods inherited from class GObject::Object

==(other : self) ==, bind_property(source_property : String, target : GObject::Object, target_property : String, flags : GObject::BindingFlags) : GObject::Binding bind_property, bind_property_full(source_property : String, target : GObject::Object, target_property : String, flags : GObject::BindingFlags, transform_to : GObject::Closure, transform_from : GObject::Closure) : GObject::Binding bind_property_full, data(key : String) : Pointer(Void) | Nil data, finalize finalize, freeze_notify : Nil freeze_notify, getv(names : Enumerable(String), values : Enumerable(_)) : Nil getv, hash(hasher) hash, notify(property_name : String) : Nil notify, notify_by_pspec(pspec : GObject::ParamSpec) : Nil notify_by_pspec, notify_signal notify_signal, property(property_name : String, value : _) : Nil property, qdata(quark : UInt32) : Pointer(Void) | Nil qdata, ref_count : UInt32 ref_count, run_dispose : Nil run_dispose, set_data(key : String, data : Pointer(Void) | Nil) : Nil set_data, set_property(property_name : String, value : _) : Nil set_property, steal_data(key : String) : Pointer(Void) | Nil steal_data, steal_qdata(quark : UInt32) : Pointer(Void) | Nil steal_qdata, thaw_notify : Nil thaw_notify, to_unsafe : Pointer(Void) to_unsafe, watch_closure(closure : GObject::Closure) : Nil watch_closure

Constructor methods inherited from class GObject::Object

cast(obj : GObject::Object) : self cast, new(pointer : Pointer(Void), transfer : GICrystal::Transfer)
new new, newv(object_type : UInt64, parameters : Enumerable(GObject::Parameter)) : self newv

Class methods inherited from class GObject::Object

cast?(obj : GObject::Object) : self | Nil cast?, compat_control(what : UInt64, data : Pointer(Void) | Nil) : UInt64 compat_control, g_type : UInt64 g_type, interface_find_property(g_iface : GObject::TypeInterface, property_name : String) : GObject::ParamSpec interface_find_property, interface_list_properties(g_iface : GObject::TypeInterface) : Enumerable(GObject::ParamSpec) interface_list_properties

Macros inherited from class GObject::Object

previous_vfunc(*args) previous_vfunc, previous_vfunc!(*args) previous_vfunc!, signal(signature) signal

Constructor Detail

def self.new(mode : Gtk::SizeGroupMode) : self #

Create a new Gtk::SizeGroup.


def self.new #

Initialize a new SizeGroup.


def self.new(*, mode : Gtk::SizeGroupMode | Nil = nil) #

Class Method Detail

def self.g_type : UInt64 #

Returns the type id (GType) registered in GLib type system.


Instance Method Detail

def ==(other : self) #
Description copied from class Reference

Returns true if this reference is the same as other. Invokes same?.


def add_widget(widget : Gtk::Widget) : Nil #

Adds a widget to a Gtk::SizeGroup.

In the future, the requisition of the widget will be determined as the maximum of its requisition and the requisition of the other widgets in the size group. Whether this applies horizontally, vertically, or in both directions depends on the mode of the size group. See Gtk::SizeGroup#mode=.

When the widget is destroyed or no longer referenced elsewhere, it will be removed from the size group.


def hash(hasher) #
Description copied from class Reference

See Object#hash(hasher)


def mode : Gtk::SizeGroupMode #

Gets the current mode of the size group.


def mode=(mode : Gtk::SizeGroupMode) : Nil #

Sets the Gtk::SizeGroupMode of the size group.

The mode of the size group determines whether the widgets in the size group should all have the same horizontal requisition (%GTK_SIZE_GROUP_HORIZONTAL) all have the same vertical requisition (%GTK_SIZE_GROUP_VERTICAL), or should all have the same requisition in both directions (%GTK_SIZE_GROUP_BOTH).


def remove_widget(widget : Gtk::Widget) : Nil #

Removes a widget from a Gtk::SizeGroup.


def widgets : GLib::SList #

Returns the list of widgets associated with size_group.