Struct gtk4::Label[][src]

pub struct Label(_);
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 <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:

<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 [classGtk.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 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

Implementations

Creates a new label with the given text inside it.

You can pass None to get an empty label widget.

str

The text of the label

Returns

the new Label

Creates a new Label, containing the text in str.

If characters in str 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. The mnemonic key can be used to activate another widget, chosen automatically, or explicitly using set_mnemonic_widget().

If set_mnemonic_widget() is not called, then the first activatable ancestor of the Label will be chosen as the mnemonic widget. For instance, if the label is inside a button or menu item, the button or menu item will automatically become the mnemonic widget and be activated by the mnemonic.

str

The text of the label, with an underscore in front of the mnemonic character

Returns

the new Label

Creates a new builder-pattern struct instance to construct Label objects.

This method returns an instance of LabelBuilder which can be used to create Label objects.

Gets the labels attribute list.

This is the pango::AttrList that was set on the label using set_attributes(), if any. This function does not reflect attributes that come from the labels markup (see set_markup()). If you want to get the effective attributes for the label, use pango_layout_get_attribute (gtk_label_get_layout (self)).

Returns

the attribute list, or None if none was set.

Returns the URI for the currently active link in the label.

The active link is the one under the mouse pointer or, in a selectable label, the link in which the text cursor is currently positioned.

This function is intended for use in a signal::Label::activate-link handler or for use in a signal::Widget::query-tooltip handler.

Returns

the currently active URI or None if there is none. The string is owned by GTK and must not be freed or modified.

Returns the ellipsizing position of the label.

See set_ellipsize().

Returns

pango::EllipsizeMode

Gets the extra menu model of label.

See set_extra_menu().

Returns

the menu model

Returns the justification of the label.

See set_justify().

Returns

Justification

Fetches the text from a label.

The returned text includes any embedded underlines indicating mnemonics and Pango markup. (See text()).

Returns

the text of the label widget. This string is owned by the widget and must not be modified or freed.

Gets the pango::Layout used to display the label.

The layout is useful to e.g. convert text positions to pixel positions, in combination with layout_offsets(). The returned layout is owned by the label so need not be freed by the caller. The label is free to recreate its layout at any time, so it should be considered read-only.

Returns

the pango::Layout for this label

Obtains the coordinates where the label will draw its pango::Layout.

The coordinates are useful to convert mouse events into coordinates inside the pango::Layout, e.g. to take some action if some part of the label is clicked. Remember when using the pango::Layout functions you need to convert to and from pixels using PANGO_PIXELS() or [constantPango].

Returns

x

location to store X offset of layout, or None

y

location to store Y offset of layout, or None

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

See set_lines().

Returns

The number of lines

Retrieves the desired maximum width of label, in characters.

See set_width_chars().

Returns

the maximum width of the label in characters.

Retrieves the target of the mnemonic (keyboard shortcut) of this label.

See set_mnemonic_widget().

Returns

the target of the label’s mnemonic, or None if none has been set and the default algorithm will be used.

Returns whether the label is selectable.

Returns

true if the user can copy text from the label

Gets the selected range of characters in the label.

Returns

true if selection is non-empty

start

return location for start of selection, as a character offset

end

return location for end of selection, as a character offset

Returns whether the label is in single line mode.

Returns

true when the label is in single line mode.

Fetches the text from a label.

The returned text is as it appears on screen. This does not include any embedded underlines indicating mnemonics or Pango markup. (See label())

Returns

the text in the label widget. This is the internal string used by the label, and must not be modified.

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

See set_use_markup().

Returns

true if the label’s text will be parsed for markup.

Returns whether an embedded underlines in the label indicate mnemonics.

See set_use_underline().

Returns

true whether an embedded underline in the label indicates the mnemonic accelerator keys.

Retrieves the desired width of label, in characters.

See set_width_chars().

Returns

the width of the label in characters.

Returns whether lines in the label are automatically wrapped.

See set_wrap().

Returns

true if the lines of the label are automatically wrapped.

Returns line wrap mode used by the label.

See set_wrap_mode().

Returns

true if the lines of the label are automatically wrapped.

Gets the xalign of the label.

See the property::Label::xalign property.

Returns

the xalign property

Gets the yalign of the label.

See the property::Label::yalign property.

Returns

the yalign property

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

See set_selectable(). If the label is not selectable, this function has no effect. If start_offset or end_offset are -1, then the end of the label will be substituted.

start_offset

start offset (in characters not bytes)

end_offset

end offset (in characters not bytes)

Apply attributes to the label text.

The attributes set with this function will be applied and merged with any other attributes previously effected by way of the property::Label::use-underline or property::Label::use-markup properties. While it is not recommended to mix markup strings with manually set attributes, if you must; know that the attributes will be applied to the label after the markup string is parsed.

attrs

a pango::AttrList, or None

Sets the mode used to ellipsizei the text.

The text will be ellipsized if there is not enough space to render the entire string.

mode

a pango::EllipsizeMode

Sets a menu model to add when constructing the context menu for label.

model

a GMenuModel

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

Justification::Left is the default value when the widget is first created with new(). If you instead want to set the alignment of the label as a whole, use WidgetExt::set_halign() instead. set_justify() has no effect on labels containing only a single line.

jtype

a Justification

Sets the text of the label.

The label is interpreted as including embedded underlines and/or Pango markup depending on the values of the property::Label::use-underline and property::Label::use-markup properties.

str

the new text to set for the label

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

This has no effect if the label is not wrapping or ellipsized. Set this to -1 if you don’t want to limit the number of lines.

lines

the desired number of lines, or -1

Sets the labels text and attributes from markup.

The string must be marked up with Pango markup (see parse_markup()).

If the str is external data, you may need to escape it with g_markup_escape_text() or g_markup_printf_escaped():

⚠️ The following code is in c ⚠️

GtkWidget *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);

This function will set the property::Label::use-markup property to true as a side effect.

If you set the label contents using the property::Label::label property you should also ensure that you set the property::Label::use-markup property accordingly.

See also: set_text()

str

a markup string

Sets the labels text, attributes and mnemonic from markup.

Parses str which is marked up with Pango markup (see parse_markup()), setting the label’s text and attribute list based on the parse results. If characters in str are preceded by an underscore, they are underlined indicating that they represent a keyboard accelerator called a mnemonic.

The mnemonic key can be used to activate another widget, chosen automatically, or explicitly using methodGtk.set_mnemonic_widget].

str

a markup string

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

n_chars

the new desired maximum width, in characters.

Associate the label with its mnemonic target.

If the label has been set so that it has a mnemonic key (using i.e. set_markup_with_mnemonic(), set_text_with_mnemonic(), with_mnemonic() or the property::Label::use_underline property) the label can be associated with a widget that is the target of the mnemonic. When the label is inside a widget (like a Button or a Notebook tab) it is automatically associated with the correct widget, but sometimes (i.e. when the target is a Entry next to the label) you need to set it explicitly using this function.

The target widget will be accelerated by emitting the signal::GtkWidget::mnemonic-activate signal on it. The default handler for this signal will activate the widget if there are no mnemonic collisions and toggle focus between the colliding widgets otherwise.

widget

the target Widget, or None to unset

Makes text in the label selectable.

Selectable labels allow the user to select text from the label, for copy-and-paste.

setting

true to allow selecting text in the label

Sets whether the label is in single line mode.

single_line_mode

true if the label should be in single line mode

Sets the text within the Label widget.

It overwrites any text that was there before.

This function will clear any previously set mnemonic accelerators, and set the property::Label::use-underline property] to false as a side effect.

This function will set the property::Label::use-markup property to false as a side effect.

See also: set_markup()

str

The text you want to set

Sets the label’s text from the string str.

If characters in str are preceded by an underscore, they are underlined indicating that they represent a keyboard accelerator called a mnemonic. The mnemonic key can be used to activate another widget, chosen automatically, or explicitly using set_mnemonic_widget().

str

a string

Sets whether the text of the label contains markup.

See set_markup().

setting

true if the label’s text should be parsed for markup.

Sets whether underlines in the text indicate mnemonics.

setting

true if underlines in the text indicate mnemonics

Sets the desired width in characters of label to n_chars.

n_chars

the new desired width, in characters.

Toggles line wrapping within the Label widget.

true makes it break lines if text exceeds the widget’s size. false lets the text get cut off by the edge of the widget if it exceeds the widget size.

Note that setting line wrapping to true does not make the label wrap at its parent container’s width, because GTK widgets conceptually can’t make their requisition depend on the parent container’s size. For a label that wraps at a specific position, set the label’s width using WidgetExt::set_size_request().

wrap

the setting

Controls how line wrapping is done.

This only affects the label if line wrapping is on. (See set_wrap()) The default is pango::WrapMode::Word which means wrap on word boundaries.

wrap_mode

the line wrapping mode

Sets the xalign of the label.

See the property::Label::xalign property.

xalign

the new xalign value, between 0 and 1

Sets the yalign of the label.

See the property::Label::yalign property.

yalign

the new yalign value, between 0 and 1

Gets emitted when the user activates a link in the label.

The ::activate-current-link is a keybinding signal.

Applications may also emit the signal with g_signal_emit_by_name() if they need to control activation of URIs programmatically.

The default bindings for this signal are all forms of the Enter key.

Gets emitted to activate a URI.

Applications may connect to it to override the default behaviour, which is to call show_uri().

uri

the URI that is activated

Returns

true if the link has been activated

Gets emitted to copy the slection to the clipboard.

The ::copy-clipboard signal is a keybinding signal.

The default binding for this signal is Ctrl-c.

Gets emitted when the user initiates a cursor movement.

The ::move-cursor signal is a keybinding signal. If the cursor is not visible in entry, this signal causes the viewport to be moved instead.

Applications should not connect to it, but may emit it with g_signal_emit_by_name() if they need to control the cursor programmatically.

The default bindings for this signal come in two variants, the variant with the Shift modifier extends the selection, the variant without the Shift modifier does not. There are too many key combinations to list them all here.

  • Arrow keys move by individual characters/lines
  • Ctrl-arrow key combinations move by words/paragraphs
  • Home/End keys move to the ends of the buffer

step

the granularity of the move, as a MovementStep

count

the number of step units to move

extend_selection

true if the move should extend the selection

Return the mnemonic accelerator.

If the label has been set so that it has a mnemonic key this function returns the keyval used for the mnemonic accelerator. If there is no mnemonic set up it returns GDK_KEY_VoidSymbol.

Returns

GDK keyval usable for accelerators, or GDK_KEY_VoidSymbol

Trait Implementations

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