Package org.gnome.gtk

Class Label

java.lang.Object
io.github.jwharm.javagi.base.ProxyInstance
org.gnome.gobject.TypeInstance
org.gnome.gobject.GObject
org.gnome.gobject.InitiallyUnowned
org.gnome.gtk.Widget
org.gnome.gtk.Label
All Implemented Interfaces:
Proxy, Accessible, AccessibleText, Buildable, ConstraintTarget
@Generated("io.github.jwharm.JavaGI") public class Label extends Widget implements Accessible, AccessibleText, Buildable, ConstraintTarget
Displays a small amount of text.

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

<picture> <source srcset="label-dark.png" media="(prefers-color-scheme: dark)"> <img alt="An example GtkLabel" src="label.png"> </picture>

Shortcuts and Gestures
GtkLabel supports the following keyboard shortcuts, when the cursor is visible:

  • Shift+F10 or Menu opens the context menu.
  • Ctrl+A or Ctrl+&amp;sol; selects all.
  • Ctrl+Shift+A or Ctrl+&amp;bsol; unselects all.

Additionally, the following signals have default keybindings:

  • Gtk.Label::activate-current-link
  • Gtk.Label::copy-clipboard
  • Gtk.Label::move-cursor

Actions
GtkLabel 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]

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 GtkShortcutsWindow, 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
GtkLabel 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 withMnemonic(java.lang.String) or setTextWithMnemonic(java.lang.String).

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 setMnemonicWidget(org.gnome.gtk.Widget).

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

// 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: 

// 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 setMnemonicWidget(org.gnome.gtk.Widget): 

// 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: 

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, Pango.parseMarkup(java.lang.String, int, int, io.github.jwharm.javagi.base.Out<org.gnome.pango.AttrList>, io.github.jwharm.javagi.base.Out<java.lang.String>, io.github.jwharm.javagi.base.Out<java.lang.Integer>))

The markup passed to setMarkup(java.lang.String) must be valid XML; for example, literal <, > and & characters must be escaped as &lt;, &gt;, and &amp;. If you pass text obtained from the user, file, or a network to setMarkup(java.lang.String), you’ll want to escape it with GLib.markupEscapeText(java.lang.String, long) or GLib.markupPrintfEscaped(java.lang.String, java.lang.Object...).

Markup strings are just a convenient way to set the Pango.AttrList on a label; setAttributes(org.gnome.pango.AttrList) 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 setSelectable(boolean). 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 setWrap(boolean).

setJustify(org.gnome.gtk.Justification) 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 Gtk.Label:width-chars and 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: 

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...";
 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 Gtk.Label::activate-link signal and the getCurrentUri() function.