Struct gtk4::Label

source ·

#[repr(transparent)]
pub struct Label { /* private fields */ }

Expand description

The Label widget displays a small amount of text.

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

An example GtkLabel

CSS nodes

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

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 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.

GtkLabel as GtkBuildable

The GtkLabel implementation of the GtkBuildable 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:

<object class="GtkLabel">
  <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

Label uses the 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 with_mnemonic() or set_text_with_mnemonic().

Mnemonics automatically activate any activatable widget the label is inside, such as a Button; if the label is not inside the mnemonic’s target widget, you have to tell the label about the target using [class@Gtk.Label.set_mnemonic_widget]. Here’s a simple example where the label is inside a button:

⚠️ The following code is in c ⚠️

// Pressing Alt+H will activate this button
GtkWidget *button = gtk_button_new ();
GtkWidget *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:

⚠️ The following code is in c ⚠️

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

To create a mnemonic for a widget alongside the label, such as a Entry, you have to point the label at the entry with set_mnemonic_widget():

⚠️ The following code is in c ⚠️

// Pressing Alt+H will focus the entry
GtkWidget *entry = gtk_entry_new ();
GtkWidget *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: ⚠️ The following code is in c ⚠️

GtkWidget *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, parse_markup())

The markup passed to gtk_label_set_markup() must be valid; for example, literal <, > and & characters must be escaped as <, >, and &. If you pass text obtained from the user, file, or a network to set_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; set_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 set_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 set_wrap().

set_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 property::Widget::halign and property::Widget::valign properties.

The property::Label::width-chars and property::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:

⚠️ 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...";
GtkWidget *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::Label::activate-link signal and the current_uri() function.

Implements

WidgetExt, glib::ObjectExt, AccessibleExt, BuildableExt, ConstraintTargetExt, WidgetExtManual, AccessibleExtManual

Struct gtk4::Label

Implementations§

impl Label

pub fn new(str: Option<&str>) -> Label

pub fn with_mnemonic(str: &str) -> Label

pub fn builder() -> LabelBuilder

pub fn attributes(&self) -> Option<AttrList>

pub fn current_uri(&self) -> Option<GString>

pub fn ellipsize(&self) -> EllipsizeMode

pub fn extra_menu(&self) -> Option<MenuModel>

pub fn justify(&self) -> Justification

pub fn label(&self) -> GString

pub fn layout(&self) -> Layout

pub fn layout_offsets(&self) -> (i32, i32)

pub fn lines(&self) -> i32

pub fn max_width_chars(&self) -> i32

pub fn mnemonic_widget(&self) -> Option<Widget>

pub fn natural_wrap_mode(&self) -> NaturalWrapMode

pub fn is_selectable(&self) -> bool

pub fn selection_bounds(&self) -> Option<(i32, i32)>

pub fn is_single_line_mode(&self) -> bool

pub fn text(&self) -> GString

pub fn uses_markup(&self) -> bool

pub fn uses_underline(&self) -> bool

pub fn width_chars(&self) -> i32

pub fn wraps(&self) -> bool

pub fn wrap_mode(&self) -> WrapMode

pub fn xalign(&self) -> f32

pub fn yalign(&self) -> f32

pub fn select_region(&self, start_offset: i32, end_offset: i32)

pub fn set_attributes(&self, attrs: Option<&AttrList>)

pub fn set_ellipsize(&self, mode: EllipsizeMode)

pub fn set_extra_menu(&self, model: Option<&impl IsA<MenuModel>>)

pub fn set_justify(&self, jtype: Justification)

pub fn set_label(&self, str: &str)

pub fn set_lines(&self, lines: i32)

pub fn set_markup(&self, str: &str)

pub fn set_markup_with_mnemonic(&self, str: &str)

pub fn set_max_width_chars(&self, n_chars: i32)

pub fn set_mnemonic_widget(&self, widget: Option<&impl IsA<Widget>>)

pub fn set_natural_wrap_mode(&self, wrap_mode: NaturalWrapMode)

pub fn set_selectable(&self, setting: bool)

pub fn set_single_line_mode(&self, single_line_mode: bool)

pub fn set_text(&self, str: &str)

pub fn set_text_with_mnemonic(&self, str: &str)

pub fn set_use_markup(&self, setting: bool)

pub fn set_use_underline(&self, setting: bool)

pub fn set_width_chars(&self, n_chars: i32)

pub fn set_wrap(&self, wrap: bool)

pub fn set_wrap_mode(&self, wrap_mode: WrapMode)

pub fn set_xalign(&self, xalign: f32)

pub fn set_yalign(&self, yalign: f32)

pub fn connect_activate_current_link<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn emit_activate_current_link(&self)

pub fn connect_activate_link<F: Fn(&Self, &str) -> Inhibit + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_copy_clipboard<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn emit_copy_clipboard(&self)

pub fn connect_move_cursor<F: Fn(&Self, MovementStep, i32, bool) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn emit_move_cursor( &self, step: MovementStep, count: i32, extend_selection: bool )

pub fn connect_attributes_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_ellipsize_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_extra_menu_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_justify_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_label_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_lines_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_max_width_chars_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_mnemonic_keyval_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_mnemonic_widget_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_natural_wrap_mode_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_selectable_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_single_line_mode_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_use_markup_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_use_underline_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId

pub fn connect_width_chars_notify<F: Fn(&Self) + 'static>( &self, f: F ) -> SignalHandlerId