class Gtk::Button

Overview

The Gtk::Button widget is generally used to trigger a callback function that is called when the button is pressed.

An example Gtk::Button

The Gtk::Button widget can hold any valid child widget. That is, it can hold almost any other standard Gtk::Widget. The most commonly used child is the Gtk::Label.

CSS nodes

Gtk::Button has a single CSS node with name button. The node will get the style classes .image-button or .text-button, if the content is just an image or label, respectively. It may also receive the .flat style class. When activating a button via the keyboard, the button will temporarily gain the .keyboard-activating style class.

Other style classes that are commonly used with Gtk::Button include .suggested-action and .destructive-action. In special cases, buttons can be made round by adding the .circular style class.

Button-like widgets like Gtk::ToggleButton, Gtk::MenuButton, Gtk::VolumeButton, Gtk::LockButton, Gtk::ColorButton or Gtk::FontButton use style classes such as .toggle, .popup, .scale, .lock, .color on the button node to differentiate themselves from a plain Gtk::Button.

Accessibility

Gtk::Button uses the %GTK_ACCESSIBLE_ROLE_BUTTON role.

Included Modules

Direct Known Subclasses

Defined in:

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

Constructors

Class Method Summary

Instance Method Summary

Instance methods inherited from module Gtk::Actionable

action_name : String | Nil action_name, action_name=(value : String) : String
action_name=(value : Nil) : Nil
action_name=(action_name : String | Nil) : Nil
action_name=
, action_name? : String | Nil action_name?, action_target : GLib::Variant | Nil action_target, action_target=(value : GLib::Variant | Nil) : GLib::Variant | Nil action_target=, action_target_value : GLib::Variant | Nil action_target_value, action_target_value=(target_value : _ | Nil) : Nil action_target_value=, detailed_action_name=(detailed_action_name : String) : Nil detailed_action_name=, to_unsafe to_unsafe

Constructor methods inherited from module Gtk::Actionable

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

Class methods inherited from module Gtk::Actionable

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

Instance methods inherited from module Gtk::ConstraintTarget

to_unsafe to_unsafe

Constructor methods inherited from module Gtk::ConstraintTarget

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

Class methods inherited from module Gtk::ConstraintTarget

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

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 module Gtk::Accessible

accessible_role : Gtk::AccessibleRole accessible_role, accessible_role=(value : Gtk::AccessibleRole) : Gtk::AccessibleRole accessible_role=, reset_property(property : Gtk::AccessibleProperty) : Nil reset_property, reset_relation(relation : Gtk::AccessibleRelation) : Nil reset_relation, reset_state(state : Gtk::AccessibleState) : Nil reset_state, to_unsafe to_unsafe, update_property(properties : Enumerable(Gtk::AccessibleProperty), values : Enumerable(_)) : Nil update_property, update_relation(relations : Enumerable(Gtk::AccessibleRelation), values : Enumerable(_)) : Nil update_relation, update_state(states : Enumerable(Gtk::AccessibleState), values : Enumerable(_)) : Nil update_state

Constructor methods inherited from module Gtk::Accessible

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

Class methods inherited from module Gtk::Accessible

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

Instance methods inherited from class Gtk::Widget

==(other : self) ==, action_set_enabled(action_name : String, enabled : Bool) : Nil action_set_enabled, activate : Bool activate, activate_action(name : String, args : _ | Nil) : Bool activate_action, activate_default : Nil activate_default, add_controller(controller : Gtk::EventController) : Nil add_controller, add_css_class(css_class : String) : Nil add_css_class, add_mnemonic_label(label : Gtk::Widget) : Nil add_mnemonic_label, add_tick_callback(callback : Gtk::TickCallback) : UInt32 add_tick_callback, allocate(width : Int32, height : Int32, baseline : Int32, transform : Gsk::Transform | Nil) : Nil allocate, allocated_baseline : Int32 allocated_baseline, allocated_height : Int32 allocated_height, allocated_width : Int32 allocated_width, allocation : Gdk::Rectangle allocation, ancestor(widget_type : UInt64) : Gtk::Widget | Nil ancestor, can_focus : Bool can_focus, can_focus=(can_focus : Bool) : Nil can_focus=, can_focus? : Bool can_focus?, can_target : Bool can_target, can_target=(can_target : Bool) : Nil can_target=, can_target? : Bool can_target?, child_focus(direction : Gtk::DirectionType) : Bool child_focus, child_visible : Bool child_visible, child_visible=(child_visible : Bool) : Nil child_visible=, children : Iterator(Widget) children, clipboard : Gdk::Clipboard clipboard, compute_bounds(target : Gtk::Widget) : Graphene::Rect compute_bounds, compute_expand(orientation : Gtk::Orientation) : Bool compute_expand, compute_point(target : Gtk::Widget, point : Graphene::Point) : Graphene::Point compute_point, compute_transform(target : Gtk::Widget) : Graphene::Matrix compute_transform, contains(x : Float64, y : Float64) : Bool contains, create_pango_context : Pango::Context create_pango_context, create_pango_layout(text : String | Nil) : Pango::Layout create_pango_layout, css_classes : Enumerable(String) css_classes, css_classes=(classes : Enumerable(String)) : Nil css_classes=, css_name : String css_name, css_name=(value : String) : String
css_name=(value : Nil) : Nil
css_name=
, css_name? : String | Nil css_name?, cursor : Gdk::Cursor | Nil cursor, cursor=(cursor : Gdk::Cursor | Nil) : Nil cursor=, cursor_from_name=(name : String | Nil) : Nil cursor_from_name=, destroy_signal destroy_signal, direction : Gtk::TextDirection direction, direction=(dir : Gtk::TextDirection) : Nil direction=, direction_changed_signal direction_changed_signal, display : Gdk::Display display, drag_check_threshold(start_x : Int32, start_y : Int32, current_x : Int32, current_y : Int32) : Bool drag_check_threshold, error_bell : Nil error_bell, first_child : Gtk::Widget | Nil first_child, focus_child : Gtk::Widget | Nil focus_child, focus_child=(child : Gtk::Widget | Nil) : Nil focus_child=, focus_on_click : Bool focus_on_click, focus_on_click=(focus_on_click : Bool) : Nil focus_on_click=, focus_on_click? : Bool focus_on_click?, focusable : Bool focusable, focusable=(focusable : Bool) : Nil focusable=, focusable? : Bool focusable?, font_map : Pango::FontMap | Nil font_map, font_map=(font_map : Pango::FontMap | Nil) : Nil font_map=, font_options : Cairo::FontOptions | Nil font_options, font_options=(options : Cairo::FontOptions | Nil) : Nil font_options=, frame_clock : Gdk::FrameClock | Nil frame_clock, grab_focus : Bool grab_focus, halign : Gtk::Align halign, halign=(align : Gtk::Align) : Nil halign=, has_css_class(css_class : String) : Bool has_css_class, has_default : Bool has_default, has_default? : Bool has_default?, has_focus : Bool has_focus, has_focus? : Bool has_focus?, has_tooltip : Bool has_tooltip, has_tooltip=(has_tooltip : Bool) : Nil has_tooltip=, has_tooltip? : Bool has_tooltip?, has_visible_focus : Bool has_visible_focus, hash(hasher) hash, height : Int32 height, height_request : Int32 height_request, height_request=(value : Int32) : Int32 height_request=, hexpand : Bool hexpand, hexpand=(expand : Bool) : Nil hexpand=, hexpand? : Bool hexpand?, hexpand_set : Bool hexpand_set, hexpand_set=(set : Bool) : Nil hexpand_set=, hexpand_set? : Bool hexpand_set?, hide : Nil hide, hide_signal hide_signal, in_destruction : Bool in_destruction, init_template : Nil init_template, insert_action_group(name : String, group : Gio::ActionGroup | Nil) : Nil insert_action_group, insert_after(parent : Gtk::Widget, previous_sibling : Gtk::Widget | Nil) : Nil insert_after, insert_before(parent : Gtk::Widget, next_sibling : Gtk::Widget | Nil) : Nil insert_before, is_ancestor(ancestor : Gtk::Widget) : Bool is_ancestor, is_drawable : Bool is_drawable, is_focus : Bool is_focus, is_sensitive : Bool is_sensitive, is_visible : Bool is_visible, keynav_failed(direction : Gtk::DirectionType) : Bool keynav_failed, keynav_failed_signal keynav_failed_signal, last_child : Gtk::Widget | Nil last_child, layout_manager : Gtk::LayoutManager | Nil layout_manager, layout_manager=(layout_manager : Gtk::LayoutManager | Nil) : Nil layout_manager=, list_mnemonic_labels : GLib::List list_mnemonic_labels, map : Nil map, map_signal map_signal, mapped : Bool mapped, margin_bottom : Int32 margin_bottom, margin_bottom=(margin : Int32) : Nil margin_bottom=, margin_end : Int32 margin_end, margin_end=(margin : Int32) : Nil margin_end=, margin_start : Int32 margin_start, margin_start=(margin : Int32) : Nil margin_start=, margin_top : Int32 margin_top, margin_top=(margin : Int32) : Nil margin_top=, measure(orientation : Gtk::Orientation, for_size : Int32) : Nil measure, mnemonic_activate(group_cycling : Bool) : Bool mnemonic_activate, mnemonic_activate_signal mnemonic_activate_signal, move_focus_signal move_focus_signal, name : String name, name=(name : String) : Nil
name=(value : Nil) : Nil
name=
, name? : String | Nil name?, native : Gtk::Native | Nil native, next_sibling : Gtk::Widget | Nil next_sibling, observe_children : Gio::ListModel observe_children, observe_controllers : Gio::ListModel observe_controllers, opacity : Float64 opacity, opacity=(opacity : Float64) : Nil opacity=, overflow : Gtk::Overflow overflow, overflow=(overflow : Gtk::Overflow) : Nil overflow=, pango_context : Pango::Context pango_context, parent : Gtk::Widget | Nil parent, parent=(parent : Gtk::Widget) : Nil parent=, pick(x : Float64, y : Float64, flags : Gtk::PickFlags) : Gtk::Widget | Nil pick, preferred_size : Gtk::Requisition preferred_size, prev_sibling : Gtk::Widget | Nil prev_sibling, primary_clipboard : Gdk::Clipboard primary_clipboard, query_tooltip_signal query_tooltip_signal, queue_allocate : Nil queue_allocate, queue_draw : Nil queue_draw, queue_resize : Nil queue_resize, realize : Nil realize, realize_signal realize_signal, realized : Bool realized, receives_default : Bool receives_default, receives_default=(receives_default : Bool) : Nil receives_default=, receives_default? : Bool receives_default?, remove_controller(controller : Gtk::EventController) : Nil remove_controller, remove_css_class(css_class : String) : Nil remove_css_class, remove_mnemonic_label(label : Gtk::Widget) : Nil remove_mnemonic_label, remove_tick_callback(id : UInt32) : Nil remove_tick_callback, request_mode : Gtk::SizeRequestMode request_mode, root : Gtk::Root | Nil root, scale_factor : Int32 scale_factor, sensitive : Bool sensitive, sensitive=(sensitive : Bool) : Nil sensitive=, sensitive? : Bool sensitive?, set_size_request(width : Int32, height : Int32) : Nil set_size_request, set_state_flags(flags : Gtk::StateFlags, clear : Bool) : Nil set_state_flags, settings : Gtk::Settings settings, should_layout : Bool should_layout, show : Nil show, show_signal show_signal, size(orientation : Gtk::Orientation) : Int32 size, size_allocate(x : Int32, y : Int32, width : Int32, height : Int32, baseline : Int32)
size_allocate(allocation : Gdk::Rectangle, baseline : Int32) : Nil
size_allocate
, size_request : Nil size_request, snapshot_child(child : Gtk::Widget, snapshot : Gtk::Snapshot) : Nil snapshot_child, state_flags : Gtk::StateFlags state_flags, state_flags_changed_signal state_flags_changed_signal, style_context : Gtk::StyleContext style_context, template_child(widget_type : UInt64, name : String) : GObject::Object
template_child(name : String) : GObject::Object
template_child
, tooltip_markup : String | Nil tooltip_markup, tooltip_markup=(value : String) : String
tooltip_markup=(value : Nil) : Nil
tooltip_markup=(markup : String | Nil) : Nil
tooltip_markup=
, tooltip_markup? : String | Nil tooltip_markup?, tooltip_text : String | Nil tooltip_text, tooltip_text=(value : String) : String
tooltip_text=(value : Nil) : Nil
tooltip_text=(text : String | Nil) : Nil
tooltip_text=
, tooltip_text? : String | Nil tooltip_text?, translate_coordinates(dest_widget : Gtk::Widget, src_x : Float64, src_y : Float64) : Bool translate_coordinates, trigger_tooltip_query : Nil trigger_tooltip_query, unmap : Nil unmap, unmap_signal unmap_signal, unparent : Nil unparent, unrealize : Nil unrealize, unrealize_signal unrealize_signal, unset_state_flags(flags : Gtk::StateFlags) : Nil unset_state_flags, valign : Gtk::Align valign, valign=(align : Gtk::Align) : Nil valign=, vexpand : Bool vexpand, vexpand=(expand : Bool) : Nil vexpand=, vexpand? : Bool vexpand?, vexpand_set : Bool vexpand_set, vexpand_set=(set : Bool) : Nil vexpand_set=, vexpand_set? : Bool vexpand_set?, visible : Bool visible, visible=(visible : Bool) : Nil visible=, visible? : Bool visible?, width : Int32 width, width_request : Int32 width_request, width_request=(value : Int32) : Int32 width_request=

Constructor methods inherited from class Gtk::Widget

new
new(*, accessible_role : Gtk::AccessibleRole | Nil = nil, can_focus : Bool | Nil = nil, can_target : Bool | Nil = nil, css_classes : Enumerable(String) | Nil = nil, css_name : String | Nil = nil, cursor : Gdk::Cursor | Nil = nil, focus_on_click : Bool | Nil = nil, focusable : Bool | Nil = nil, halign : Gtk::Align | Nil = nil, has_default : Bool | Nil = nil, has_focus : Bool | Nil = nil, has_tooltip : Bool | Nil = nil, height_request : Int32 | Nil = nil, hexpand : Bool | Nil = nil, hexpand_set : Bool | Nil = nil, layout_manager : Gtk::LayoutManager | Nil = nil, margin_bottom : Int32 | Nil = nil, margin_end : Int32 | Nil = nil, margin_start : Int32 | Nil = nil, margin_top : Int32 | Nil = nil, name : String | Nil = nil, opacity : Float64 | Nil = nil, overflow : Gtk::Overflow | Nil = nil, parent : Gtk::Widget | Nil = nil, receives_default : Bool | Nil = nil, root : Gtk::Root | Nil = nil, scale_factor : Int32 | Nil = nil, sensitive : Bool | Nil = nil, tooltip_markup : String | Nil = nil, tooltip_text : String | Nil = nil, valign : Gtk::Align | Nil = nil, vexpand : Bool | Nil = nil, vexpand_set : Bool | Nil = nil, visible : Bool | Nil = nil, width_request : Int32 | Nil = nil)
new

Class methods inherited from class Gtk::Widget

default_direction : Gtk::TextDirection default_direction, default_direction=(dir : Gtk::TextDirection) : Nil default_direction=, g_type : UInt64 g_type

Instance methods inherited from module Gtk::ConstraintTarget

to_unsafe to_unsafe

Constructor methods inherited from module Gtk::ConstraintTarget

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

Class methods inherited from module Gtk::ConstraintTarget

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

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 module Gtk::Accessible

accessible_role : Gtk::AccessibleRole accessible_role, accessible_role=(value : Gtk::AccessibleRole) : Gtk::AccessibleRole accessible_role=, reset_property(property : Gtk::AccessibleProperty) : Nil reset_property, reset_relation(relation : Gtk::AccessibleRelation) : Nil reset_relation, reset_state(state : Gtk::AccessibleState) : Nil reset_state, to_unsafe to_unsafe, update_property(properties : Enumerable(Gtk::AccessibleProperty), values : Enumerable(_)) : Nil update_property, update_relation(relations : Enumerable(Gtk::AccessibleRelation), values : Enumerable(_)) : Nil update_relation, update_state(states : Enumerable(Gtk::AccessibleState), values : Enumerable(_)) : Nil update_state

Constructor methods inherited from module Gtk::Accessible

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

Class methods inherited from module Gtk::Accessible

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

Instance methods inherited from class GObject::InitiallyUnowned

==(other : self) ==, hash(hasher) hash

Constructor methods inherited from class GObject::InitiallyUnowned

new new

Class methods inherited from class GObject::InitiallyUnowned

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 : self #

Creates a new Gtk::Button widget.

To add a child widget to the button, use Gtk::Button#child=.


[View source]
def self.new(*, accessible_role : Gtk::AccessibleRole | Nil = nil, action_name : String | Nil = nil, action_target : GLib::Variant | Nil = nil, can_focus : Bool | Nil = nil, can_target : Bool | Nil = nil, child : Gtk::Widget | Nil = nil, css_classes : Enumerable(String) | Nil = nil, css_name : String | Nil = nil, cursor : Gdk::Cursor | Nil = nil, focus_on_click : Bool | Nil = nil, focusable : Bool | Nil = nil, halign : Gtk::Align | Nil = nil, has_default : Bool | Nil = nil, has_focus : Bool | Nil = nil, has_frame : Bool | Nil = nil, has_tooltip : Bool | Nil = nil, height_request : Int32 | Nil = nil, hexpand : Bool | Nil = nil, hexpand_set : Bool | Nil = nil, icon_name : String | Nil = nil, label : String | Nil = nil, layout_manager : Gtk::LayoutManager | Nil = nil, margin_bottom : Int32 | Nil = nil, margin_end : Int32 | Nil = nil, margin_start : Int32 | Nil = nil, margin_top : Int32 | Nil = nil, name : String | Nil = nil, opacity : Float64 | Nil = nil, overflow : Gtk::Overflow | Nil = nil, parent : Gtk::Widget | Nil = nil, receives_default : Bool | Nil = nil, root : Gtk::Root | Nil = nil, scale_factor : Int32 | Nil = nil, sensitive : Bool | Nil = nil, tooltip_markup : String | Nil = nil, tooltip_text : String | Nil = nil, use_underline : Bool | Nil = nil, valign : Gtk::Align | Nil = nil, vexpand : Bool | Nil = nil, vexpand_set : Bool | Nil = nil, visible : Bool | Nil = nil, width_request : Int32 | Nil = nil) #

[View source]
def self.new_from_icon_name(icon_name : String | Nil) : self #

Creates a new button containing an icon from the current icon theme.

If the icon name isn’t known, a “broken image” icon will be displayed instead. If the current icon theme is changed, the icon will be updated appropriately.


[View source]
def self.new_with_label(label : String) : self #

Creates a Gtk::Button widget with a Gtk::Label child.


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def self.new_with_mnemonic(label : String) : self #

Creates a new Gtk::Button containing a label.

If characters in label are preceded by an underscore, they are underlined. If you need a literal underscore character in a label, use “__” (two underscores). The first underlined character represents a keyboard accelerator called a mnemonic. Pressing Alt and that key activates the button.


[View source]

Class Method Detail

def self.g_type : UInt64 #

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


[View source]

Instance Method Detail

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

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


def activate_signal #

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def child : Gtk::Widget | Nil #

Gets the child widget of button.


[View source]
def child=(child : Gtk::Widget | Nil) : Nil #

Sets the child widget of button.

Note that by using this API, you take full responsibility for setting up the proper accessibility label and description information for button. Most likely, you'll either set the accessibility label or description for button explicitly, or you'll set a labelled-by or described-by relations from child to button.


[View source]
def clicked_signal #

[View source]
def has_frame : Bool #

Returns whether the button has a frame.


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def has_frame=(has_frame : Bool) : Nil #

Sets the style of the button.

Buttons can has a flat appearance or have a frame drawn around them.


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def has_frame? : Bool #

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def hash(hasher) #
Description copied from class Reference

See Object#hash(hasher)


def icon_name : String | Nil #

Returns the icon name of the button.

If the icon name has not been set with Gtk::Button#icon_name= the return value will be nil. This will be the case if you create an empty button with Gtk::Button.new to use as a container.


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def icon_name=(icon_name : String) : Nil #

Adds a Gtk::Image with the given icon name as a child.

If button already contains a child widget, that child widget will be removed and replaced with the image.


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def icon_name=(value : Nil) : Nil #

Set #icon_name property to nil.


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def icon_name? : String | Nil #

Same as #icon_name, but can return nil.


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def label : String | Nil #

Fetches the text from the label of the button.

If the label text has not been set with Gtk::Button#label= the return value will be nil. This will be the case if you create an empty button with Gtk::Button.new to use as a container.


[View source]
def label=(label : String) : Nil #

Sets the text of the label of the button to label.

This will also clear any previously set labels.


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def label=(value : Nil) : Nil #

Set #label property to nil.


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def label? : String | Nil #

Same as #label, but can return nil.


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def use_underline : Bool #

gets whether underlines are interpreted as mnemonics.

See Gtk::Button#use_underline=.


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def use_underline=(use_underline : Bool) : Nil #

Sets whether to use underlines as mnemonics.

If true, an underline in the text of the button label indicates the next character should be used for the mnemonic accelerator key.


[View source]
def use_underline? : Bool #

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