Struct gtk::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, a MenuItem, or a ComboBox.

CSS nodes

⚠️ The following code is in plain ⚠️

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

GtkLabel 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 wth 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.

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 PangoAttribute values for this label.

An example of a UI definition fragment specifying Pango attributes:

⚠️ The following code is in xml ⚠️

<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.

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 LabelExt::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 LabelExt::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_container_add (GTK_CONTAINER (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 LabelExt::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][PangoMarkupFormat].

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 [complete documentation][PangoMarkupFormat] of available tags in the Pango manual.)

The markup passed to LabelExt::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 LabelExt::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; LabelExt::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 PangoAttribute requires knowledge of the exact string being displayed, so translations will cause problems.

Selectable labels

Labels can be made selectable with LabelExt::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 # {label-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 LabelExt::set_line_wrap().

LabelExt::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.

Note that the interpretation of property::Label::width-chars and property::Label::max-width-chars has changed a bit with the introduction of [width-for-height geometry management.][geometry-management]

Since 2.18, 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“ and “title“ 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.

An example looks like this:

⚠️ The following code is in C ⚠️

const gchar *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 LabelExt::current_uri() function.

Implements

LabelExt, [MiscExt][trait@crate::prelude::MiscExt], WidgetExt, glib::ObjectExt, BuildableExt, WidgetExtManual, BuildableExtManual

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 LabelExt::set_mnemonic_widget().

If LabelExt::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.

Trait Implementations

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

Returns the “default value” for a type. Read more

Formats the value using the given formatter. Read more

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

This method returns an ordering between self and other values if one exists. Read more

This method tests less than (for self and other) and is used by the < operator. Read more

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

This method tests greater than (for self and other) and is used by the > operator. Read more

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

Returns the type identifier of Self.

Auto Trait Implementations

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Performs the conversion.

Performs the conversion.

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Similar to Self::set_property but fails instead of panicking.

Sets the property property_name of the object to value value. Read more

Similar to Self::set_property but fails instead of panicking.

Sets the property property_name of the object to value value. Read more

Similar to Self::set_properties but fails instead of panicking.

Sets multiple properties of the object at once. Read more

Similar to Self::set_properties_from_value but fails instead of panicking.

Sets multiple properties of the object at once. Read more

Similar to Self::property but fails instead of panicking.

Gets the property property_name of the object and cast it to the type V. Read more

Similar to Self::property_value but fails instead of panicking.

Gets the property property_name of the object. Read more

Check if the object has a property property_name of the given type_. Read more

Get the type of the property property_name of this object. Read more

Get the ParamSpec of the property property_name of this object.

Return all ParamSpec of the properties of this object.

Freeze all property notifications until the return guard object is dropped. Read more

Set arbitrary data on this object with the given key. Read more

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Retrieve previously set arbitrary data of this object with the given key. Read more

Set arbitrary data on this object with the given key. Read more

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Retrieve previously set arbitrary data of this object with the given key. Read more

Block a given signal handler. Read more

Unblock a given signal handler.

Stop emission of the currently emitted signal.

Stop emission of the currently emitted signal by the (possibly detailed) signal name.

Similar to Self::connect but fails instead of panicking.

Connect to the signal signal_name on this object. Read more

Similar to Self::connect_id but fails instead of panicking.

Connect to the signal signal_id on this object. Read more

Similar to Self::connect_local but fails instead of panicking.

Connect to the signal signal_name on this object. Read more

Similar to Self::connect_local_id but fails instead of panicking.

Connect to the signal signal_id on this object. Read more

Similar to Self::connect_unsafe but fails instead of panicking.

Connect to the signal signal_name on this object. Read more

Similar to Self::connect_unsafe_id but fails instead of panicking.

Similar to Self::connect_closure but fails instead of panicking.

Connect a closure to the signal signal_name on this object. Read more

Similar to Self::connect_closure_id but fails instead of panicking.

Connect a closure to the signal signal_id on this object. Read more

Limits the lifetime of closure to the lifetime of the object. When the object’s reference count drops to zero, the closure will be invalidated. An invalidated closure will ignore any calls to Closure::invoke. Read more

Connect to the signal signal_id on this object. Read more

Similar to Self::emit but fails instead of panicking.

Emit signal by signal id. Read more

Similar to Self::emit_with_values but fails instead of panicking.

Same as Self::emit but takes Value for the arguments.

Similar to Self::emit_by_name but fails instead of panicking.

Emit signal by its name. Read more

Similar to Self::emit_by_name_with_values but fails instead of panicking.

Emit signal by its name. Read more

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Emit signal by signal id with details. Read more

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Emit signal by signal id with details. Read more

Disconnect a previously connected signal handler.

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Connect to the notify signal of the object. Read more

Notify that the given property has changed its value. Read more

Notify that the given property has changed its value. Read more

Downgrade this object to a weak reference.

Bind property source_property on this object to the target_property on the target object. Read more

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The resulting type after obtaining ownership.

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🔬 This is a nightly-only experimental API. (toowned_clone_into)

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Converts the given value to a String. Read more

The type returned in the event of a conversion error.

Performs the conversion.

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Performs the conversion.