class Gtk::Label

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

Overview

The Gtk::Label widget displays a small amount of text.

As the name implies, most labels are used to label another widget such as a #Button.

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 element, which supports any number of elements. The 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_ACCESSIBLE_ROLE_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_set_markup() must be valid; for example, literal <, > and & characters must be escaped as &lt;, >, and &. If you pass text obtained from the user, file, or a network to Gtk::Label#markup=, you’ll want to escape it with g_markup_escape_text() or g_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> 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 looks like this:

WARNING ⚠️ The following code is in c ⚠️

const char *text =
"Go to the"
"<a href=\"http://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::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, 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, 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 Gtk::Label, containing the text in str.

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 labels 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 currently active link in the label.

• #ellipsize : Pango::EllipsizeMode

  Returns the ellipsizing position of the label.

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

  Sets the mode used to ellipsizei the text.

• #extra_menu : Gio::MenuModel | Nil

  Gets the extra menu model of label.

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

  Sets a menu model to add when constructing the context menu for 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 the lines in the text of 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 desired maximum width of label, in characters.

• #max_width_chars=(n_chars : Int32) : Nil

  Sets the desired maximum width in characters of label to n_chars.

• #mnemonic_keyval : UInt32

  Return the mnemonic accelerator.

• #mnemonic_widget : Gtk::Widget | Nil

  Retrieves the target of the mnemonic (keyboard shortcut) 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 line wrap mode used by the label.

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

  Select 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
• #text : String

  Fetches the text from a label.

• #text=(str : String) : Nil

  Sets the text within the Gtk::Label widget.

• #text_with_mnemonic=(str : String) : Nil

  Sets the label’s text from the string str.

• #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 an embedded 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 label, in characters.

• #width_chars=(n_chars : Int32) : Nil

  Sets the desired width in characters of label to n_chars.

• #wrap : Bool

  Returns whether lines in the label are automatically wrapped.

• #wrap=(wrap : Bool) : Nil

  Toggles line wrapping within the Gtk::Label widget.

• #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);