gtk:widget, gobject:initially-unowned, gtk:accessible-text, gtk:accessible, gtk:buildable, gtk:constraint-target, gobject:object, common-lisp:standard-object, common-lisp:t

None

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 gtk:button widget.

Figure: GtkLabel

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 gtk:label-new-with-mnemonic or gtk:label-set-text-with-mnemonic functions.

Mnemonics automatically activate any activatable widget the label is inside, such as a gtk:button widget. If the label is not inside the target widget of the mnemonic, you have to tell the label about the target using the gtk:label-mnemonic-widget function. Here is a simple example where the label is inside a button:

;; Pressing Alt+H will activate this button
(let* ((label (gtk:label-new-with-mnemonic "_Hello"))
       (button (make-instance 'gtk:button
                              :child label)))
   ... )  

There is a convenience function to create buttons with a mnemonic label already inside:

;; Pressing Alt+H will activate this button
(gtk:button-new-with-mnemonic "_Hello")  

To create a mnemonic for a widget alongside the label, such as a gtk:entry widget, you have to point the label at the text entry with the gtk:label-mnemonic-widget function:

;; Pressing Alt+H will focus the text entry
(let ((entry (make-instance 'gtk:entry))
      (label (gtk:label-new-with-mnemonic "_Hello")))
   (setf (gtk:label-mnemonic-widget label) entry)
   ... )  

Markup (styled text)

To make it easy to format text in a label, changing colors, fonts, and so on, label text can be provided in a simple markup format. Here is how to create a label with a small font:

(let ((label (make-instance 'gtk:label)))
  (gtk:label-set-markup label
                        "<small>Small text</small>")
  ... )  

See complete documentation of available tags in the Pango manual.

The markup passed to the gtk:label-set-markup function must be valid. For example, literal <, > and & characters must be escaped as <, gt;, and &. If you pass text obtained from the user, file, or a network to the gtk:label-set-markup function, you will want to escape it with the g_markup_escape_text() or g_markup_printf_escaped() functions.

Markup strings are just a convenient way to set the pango:attr-list instance on a label. The gtk:label-attributes function may be a simpler way to set attributes in some cases. Be careful though, a pango:attr-list instance tends to cause internationalization problems, unless you are applying attributes to the entire string, that is, 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 structure requires knowledge of the exact string being displayed, so translations will cause problems.

Selectable labels

Labels can be made selectable with the gtk:label-selectable function. 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 the gtk:label-wrap function.

The gtk:label-justify function 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 halign and valign properties.

The width-chars and 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, the width-chars property is used as the minimum width, if specified, and the max-width-chars property is used as the natural width. Even if the max-width-chars property specified, wrapping labels will be rewrapped to use all of the available width.

Note that the interpretation of the width-chars and max-width-chars properties has changed a bit with the introduction of "width-for-height" geometry management.

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 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:

(gtk:label-set-markup label
                      "Go to <a href="http://gtk.org/">GTK Website</a> ...")  

It is possible to implement custom handling for links and their tooltips with the "activate-link" signal and the gtk:label-current-uri function. The gtk:label implementation of the gtk:buildable 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 the label.

Example: 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.

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

The gtk:label implementation has a single CSS node with the name label. A wide variety of style classes may be applied to labels, such as the .title, .subtitle, .dim-label style classes. In the gtk:shortcuts-window widget, 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. In this case, the label node also gets a .link style class. The gtk:label implementation uses the :label role of the gtk:accessible-role enumeration. The gtk:label implementation supports the following keyboard shortcuts, when the cursor is visible.

• Shift+F10 or Menu opens the context menu.
• Ctrl+A or Ctrl+/ selects all.
• Ctrl+Shift+A or Ctrl+ unselects all.

Additionally, the following signals have default keybindings.

• GtkLabel::activate-current-link
• GtkLabel::copy-clipboard
• GtkLabel::move-cursor

The gtk:label implementation defines a set of built-in actions.

clipboard.copy

Copies the text to the clipboard.

clipboard.cut

Does not do anything, since text in labels cannot be deleted.

clipboard.paste

Does not do anything, since text in labels cannot 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

Does not do anything, since text in labels cannot be deleted.

selection.select-all

Selects all of the text, if the label allows selection.

The "activate-current-link" signal

lambda (label)    :action      

label

The gtk:label widget on which the signal was emitted.

A keybinding signal which gets emitted when the user activates a link in the label. Applications may also emit the signal with the g:signal-emit function if they need to control activation of URIs programmatically. The default bindings for this signal are all forms of the Enter key.

The "activate-link" signal

lambda (label uri)    :run-last      

label

The gtk:label widget on which the signal was emitted.

uri

The string with the URI that is activated.

Returns

True if the link has been activated.

The signal which gets emitted to activate a URI. Applications may connect to it to override the default behaviour, which is to call the gtk:show-uri function.

The "copy-clipboard" signal

lambda (label)    :action      

label

The gtk:label widget which received the signal.

The signal is a keybinding signal which gets emitted to copy the selection to the clipboard. The default binding for this signal is the Ctrl-c key.

The "move-cursor" signal

lambda (label step count extend)    :action      

label

The gtk:label widget which received the signal.

step

The granularity of the move, as a value of the gtk:movement-step enumeration.

count

The integer with the number of step units to move.

extend

True if the move should extend the selection.

The signal is a keybinding signal which gets emitted when the user initiates a cursor movement. If the cursor is not visible in the label, this signal causes the viewport to be moved instead. Applications should not connect to it, but may emit it with the g:signal-emit function 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 modifer 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.