class Gtk::Label

• Gtk::Label
• Gtk::Widget
• GObject::InitiallyUnowned
• GObject::Object
• Reference
• Object

Overview

Displays a small amount of text.

Most labels are used to label another widget (such as an #Entry).

Shortcuts and Gestures

Gtk::Label supports the following keyboard shortcuts, when the cursor is visible:

• Shift+F10 or Menu opens the context menu.
• Ctrl+A or Ctrl+/ selects all.
• Ctrl+Shift+A or Ctrl+\ unselects all.

Additionally, the following signals have default keybindings:

• [signal@Gtk.Label::activate-current-link]
• [signal@Gtk.Label::copy-clipboard]
• [signal@Gtk.Label::move-cursor]

Actions

Gtk::Label defines a set of built-in actions:

• clipboard.copy copies the text to the clipboard.
• clipboard.cut doesn't do anything, since text in labels can't be deleted.
• clipboard.paste doesn't do anything, since text in labels can't be edited.
• link.open opens the link, when activated on a link inside the label.
• link.copy copies the link to the clipboard, when activated on a link inside the label.
• menu.popup opens the context menu.
• selection.delete doesn't do anything, since text in labels can't be deleted.
• selection.select-all selects all of the text, if the label allows selection.

CSS nodes

label
├── [selection]
├── [link]
┊
╰── [link]

Gtk::Label has a single CSS node with the name label. A wide variety of style classes may be applied to labels, such as .title, .subtitle, .dim-label, etc. In the Gtk::ShortcutsWindow, labels are used with the .keycap style class.

If the label has a selection, it gets a subnode with name selection.

If the label has links, there is one subnode per link. These subnodes carry the link or visited state depending on whether they have been visited. In this case, label node also gets a .link style class.

Gtk::Label as Gtk::Buildable

The Gtk::Label implementation of the Gtk::Buildable interface supports a custom <attributes> element, which supports any number of <attribute> elements. The <attribute> element has attributes named “name“, “value“, “start“ and “end“ and allows you to specify Pango::Attribute values for this label.

An example of a UI definition fragment specifying Pango attributes:

WARNING ⚠️ The following code is in xml ⚠️

<object class="Gtk::Label">
  <attributes>
    <attribute name="weight" value="PANGO_WEIGHT_BOLD"/>
    <attribute name="background" value="red" start="5" end="10"/>
  </attributes>
</object>

The start and end attributes specify the range of characters to which the Pango attribute applies. If start and end are not specified, the attribute is applied to the whole text. Note that specifying ranges does not make much sense with translatable attributes. Use markup embedded in the translatable content instead.

Accessibility

Gtk::Label uses the Gtk::AccessibleRole#label role.

Mnemonics

Labels may contain “mnemonics”. Mnemonics are underlined characters in the label, used for keyboard navigation. Mnemonics are created by providing a string with an underscore before the mnemonic character, such as "_File", to the functions Gtk::Label#new_with_mnemonic or Gtk::Label#text_with_mnemonic=.

Mnemonics automatically activate any activatable widget the label is inside, such as a Gtk::Button; if the label is not inside the mnemonic’s target widget, you have to tell the label about the target using Gtk::Label#mnemonic_widget=.

Here’s a simple example where the label is inside a button:

WARNING ⚠️ The following code is in c ⚠️

// Pressing Alt+H will activate this button
Gtk::Widget *button = gtk_button_new ();
Gtk::Widget *label = gtk_label_new_with_mnemonic ("_Hello");
gtk_button_set_child (GTK_BUTTON (button), label);

There’s a convenience function to create buttons with a mnemonic label already inside:

WARNING ⚠️ The following code is in c ⚠️

// Pressing Alt+H will activate this button
Gtk::Widget *button = gtk_button_new_with_mnemonic ("_Hello");

To create a mnemonic for a widget alongside the label, such as a Gtk::Entry, you have to point the label at the entry with Gtk::Label#mnemonic_widget=:

WARNING ⚠️ The following code is in c ⚠️

// Pressing Alt+H will focus the entry
Gtk::Widget *entry = gtk_entry_new ();
Gtk::Widget *label = gtk_label_new_with_mnemonic ("_Hello");
gtk_label_set_mnemonic_widget (GTK_LABEL (label), entry);

Markup (styled text)

To make it easy to format text in a label (changing colors, fonts, etc.), label text can be provided in a simple markup format:

Here’s how to create a label with a small font:

WARNING ⚠️ The following code is in c ⚠️

Gtk::Widget *label = gtk_label_new (NULL);
gtk_label_set_markup (GTK_LABEL (label), "<small>Small text</small>");

(See the Pango manual for complete documentation] of available tags, Pango::parse_markup)

The markup passed to Gtk::Label#markup= must be valid XML; for example, literal <, > and & characters must be escaped as <, >, and &. If you pass text obtained from the user, file, or a network to Gtk::Label#markup=, you’ll want to escape it with GLib::markup_escape_text or GLib::markup_printf_escaped.

Markup strings are just a convenient way to set the Pango::AttrList on a label; Gtk::Label#attributes= may be a simpler way to set attributes in some cases. Be careful though; Pango::AttrList tends to cause internationalization problems, unless you’re applying attributes to the entire string (i.e. unless you set the range of each attribute to [0, G_MAXINT)). The reason is that specifying the start_index and end_index for a Pango::Attribute requires knowledge of the exact string being displayed, so translations will cause problems.

Selectable labels

Labels can be made selectable with Gtk::Label#selectable=. Selectable labels allow the user to copy the label contents to the clipboard. Only labels that contain useful-to-copy information — such as error messages — should be made selectable.

Text layout

A label can contain any number of paragraphs, but will have performance problems if it contains more than a small number. Paragraphs are separated by newlines or other paragraph separators understood by Pango.

Labels can automatically wrap text if you call Gtk::Label#wrap=.

Gtk::Label#justify= sets how the lines in a label align with one another. If you want to set how the label as a whole aligns in its available space, see the Gtk::Widget#halign and Gtk::Widget#valign properties.

The [property@Gtk.Label:width-chars] and [property@Gtk.Label:max-width-chars] properties can be used to control the size allocation of ellipsized or wrapped labels. For ellipsizing labels, if either is specified (and less than the actual text size), it is used as the minimum width, and the actual text size is used as the natural width of the label. For wrapping labels, width-chars is used as the minimum width, if specified, and max-width-chars is used as the natural width. Even if max-width-chars specified, wrapping labels will be rewrapped to use all of the available width.

Links

GTK supports markup for clickable hyperlinks in addition to regular Pango markup. The markup for links is borrowed from HTML, using the <a> tag with “href“, “title“ and “class“ attributes. GTK renders links similar to the way they appear in web browsers, with colored, underlined text. The “title“ attribute is displayed as a tooltip on the link. The “class“ attribute is used as style class on the CSS node for the link.

An example of inline links looks like this:

WARNING ⚠️ The following code is in c ⚠️

const char *text =
"Go to the "
"<a href=\"https://www.gtk.org\" title=\"&lt;i&gt;Our&lt;/i&gt; website\">"
"GTK website</a> for more...";
Gtk::Widget *label = gtk_label_new (NULL);
gtk_label_set_markup (GTK_LABEL (label), text);

It is possible to implement custom handling for links and their tooltips with the [signal@Gtk.Label::activate-link] signal and the Gtk::Label#current_uri function.

Included Modules

• Gtk::Accessible
• Gtk::AccessibleText
• Gtk::Buildable
• Gtk::ConstraintTarget

Defined in:

Constructors

• .new(str : String | Nil) : self

  Creates a new label with the given text inside it.

• .new

  Initialize a new Label.

• .new(*, accessible_role : Gtk::AccessibleRole | Nil = nil, attributes : Pango::AttrList | 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, ellipsize : Pango::EllipsizeMode | Nil = nil, extra_menu : Gio::MenuModel | 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, justify : Gtk::Justification | Nil = nil, label : String | Nil = nil, layout_manager : Gtk::LayoutManager | Nil = nil, limit_events : Bool | Nil = nil, lines : Int32 | Nil = nil, margin_bottom : Int32 | Nil = nil, margin_end : Int32 | Nil = nil, margin_start : Int32 | Nil = nil, margin_top : Int32 | Nil = nil, max_width_chars : Int32 | Nil = nil, mnemonic_keyval : UInt32 | Nil = nil, mnemonic_widget : Gtk::Widget | Nil = nil, name : String | Nil = nil, natural_wrap_mode : Gtk::NaturalWrapMode | 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, selectable : Bool | Nil = nil, sensitive : Bool | Nil = nil, single_line_mode : Bool | Nil = nil, tabs : Pango::TabArray | Nil = nil, tooltip_markup : String | Nil = nil, tooltip_text : String | Nil = nil, use_markup : Bool | 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_chars : Int32 | Nil = nil, width_request : Int32 | Nil = nil, wrap : Bool | Nil = nil, wrap_mode : Pango::WrapMode | Nil = nil, xalign : Float32 | Nil = nil, yalign : Float32 | Nil = nil)
• .new_with_mnemonic(str : String | Nil) : self

  Creates a new label with the given text inside it, and a mnemonic.

Class Method Summary

• .g_type : UInt64

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

Instance Method Summary

• #==(other : self)

  Returns true if this reference is the same as other.

• #activate_current_link_signal
• #activate_link_signal
• #attributes : Pango::AttrList | Nil

  Gets the label's attribute list.

• #attributes=(attrs : Pango::AttrList | Nil) : Nil

  Apply attributes to the label text.

• #copy_clipboard_signal
• #current_uri : String | Nil

  Returns the URI for the active link in the label.

• #ellipsize : Pango::EllipsizeMode

  Returns the ellipsization mode of the label.

• #ellipsize=(mode : Pango::EllipsizeMode) : Nil

  Sets the mode used to ellipsize the text.

• #extra_menu : Gio::MenuModel | Nil

  Gets the extra menu model of the label.

• #extra_menu=(model : Gio::MenuModel | Nil) : Nil

  Sets a menu model to add to the context menu of the label.

• #hash(hasher)

  See Object#hash(hasher)

• #justify : Gtk::Justification

  Returns the justification of the label.

• #justify=(jtype : Gtk::Justification) : Nil

  Sets the alignment of lines in the label relative to each other.

• #label : String

  Fetches the text from a label.

• #label=(str : String) : Nil

  Sets the text of the label.

• #label=(value : Nil) : Nil

  Set #label property to nil.

• #label? : String | Nil

  Same as #label, but can return nil.

• #layout : Pango::Layout

  Gets the Pango layout used to display the label.

• #layout_offsets : Nil

  Obtains the coordinates where the label will draw its Pango layout.

• #lines : Int32

  Gets the number of lines to which an ellipsized, wrapping label should be limited.

• #lines=(lines : Int32) : Nil

  Sets the number of lines to which an ellipsized, wrapping label should be limited.

• #markup=(str : String) : Nil

  Sets the labels text and attributes from markup.

• #markup_with_mnemonic=(str : String) : Nil

  Sets the labels text, attributes and mnemonic from markup.

• #max_width_chars : Int32

  Retrieves the maximum width of the label in characters.

• #max_width_chars=(n_chars : Int32) : Nil

  Sets the maximum width of the label in characters.

• #mnemonic_keyval : UInt32

  Return the mnemonic accelerator.

• #mnemonic_widget : Gtk::Widget | Nil

  Retrieves the mnemonic target of this label.

• #mnemonic_widget=(widget : Gtk::Widget | Nil) : Nil

  Associate the label with its mnemonic target.

• #move_cursor_signal
• #natural_wrap_mode : Gtk::NaturalWrapMode

  Returns natural line wrap mode used by the label.

• #natural_wrap_mode=(wrap_mode : Gtk::NaturalWrapMode) : Nil

  Selects the line wrapping for the natural size request.

• #select_region(start_offset : Int32, end_offset : Int32) : Nil

  Selects a range of characters in the label, if the label is selectable.

• #selectable : Bool

  Returns whether the label is selectable.

• #selectable=(setting : Bool) : Nil

  Makes text in the label selectable.

• #selectable? : Bool
• #selection_bounds : Bool

  Gets the selected range of characters in the label.

• #single_line_mode : Bool

  Returns whether the label is in single line mode.

• #single_line_mode=(single_line_mode : Bool) : Nil

  Sets whether the label is in single line mode.

• #single_line_mode? : Bool
• #tabs : Pango::TabArray | Nil

  Gets the tab stops for the label.

• #tabs=(tabs : Pango::TabArray | Nil) : Nil

  Sets tab stops for the label.

• #text : String

  Gets the text of the label.

• #text=(str : String) : Nil

  Sets the text for the label.

• #text_with_mnemonic=(str : String) : Nil

  Sets the text for the label, with mnemonics.

• #use_markup : Bool

  Returns whether the label’s text is interpreted as Pango markup.

• #use_markup=(setting : Bool) : Nil

  Sets whether the text of the label contains markup.

• #use_markup? : Bool
• #use_underline : Bool

  Returns whether underlines in the label indicate mnemonics.

• #use_underline=(setting : Bool) : Nil

  Sets whether underlines in the text indicate mnemonics.

• #use_underline? : Bool
• #width_chars : Int32

  Retrieves the desired width of the label in characters.

• #width_chars=(n_chars : Int32) : Nil

  Sets the desired width in characters of the label.

• #wrap : Bool

  Returns whether lines in the label are automatically wrapped.

• #wrap=(wrap : Bool) : Nil

  Toggles line wrapping within the label.

• #wrap? : Bool
• #wrap_mode : Pango::WrapMode

  Returns line wrap mode used by the label.

• #wrap_mode=(wrap_mode : Pango::WrapMode) : Nil

  Controls how line wrapping is done.

• #xalign : Float32

  Gets the #xalign of the label.

• #xalign=(xalign : Float32) : Nil

  Sets the #xalign of the label.

• #yalign : Float32

  Gets the #yalign of the label.

• #yalign=(yalign : Float32) : Nil

  Sets the #yalign of the label.

Constructor Detail

Class Method Detail

Instance Method Detail

Gtk::Widget *self = gtk_label_new (NULL);
const char *str = "...";
const char *format = "<span style=\"italic\">\%s</span>";
char *markup;

markup = g_markup_printf_escaped (format, str);
gtk_label_set_markup (GTK_LABEL (self), markup);
g_free (markup);