Class gtk-label

Package: gtk

Superclasses

gtk-misc, gtk-widget, gtk-buildable, g-object, common-lisp:standard-object, common-lisp:t

Documented Subclasses

gtk-accel-label

Direct Slots

angle

The angle property of type :double (Read / Write)
The angle that the baseline of the label makes with the horizontal, in degrees, measured counterclockwise. An angle of 90 degrees reads from bottom to top, an angle of 270 degrees, from top to bottom. Ignored if the label is selectable, wrapped, or ellipsized.
Allowed values: [0.0, 360.0]
Default value: 0.0

attributes

The attributes property of type pango-attr-list (Read / Write)
A list of style attributes to apply to the text of the label.

cursor-position

The cursor-position property of type :int (Read)
The current position of the insertion cursor in chars.
Allowed values: >= 0
Default value: 0

ellipsize

The ellipsize property of type pango-ellipsize-mode (Read / Write)
The preferred place to ellipsize the string, if the label does not have enough room to display the entire string, specified as a value of the pango-ellipsize-mode enumeration. Note that setting this property to a value other than :none has the side-effect that the label requests only enough space to display the ellipsis "...". In particular, this means that ellipsizing labels do not work well in notebook tabs, unless the tab-expand child property of the tab is set to true. Other ways to set a width of the label are the gtk-widget-size-request and gtk-label-width-chars functions.
Default value: :none

justify

The justify property of type gtk-justification (Read / Write)
The alignment of the lines in the text of the label relative to each other. This does not affect the alignment of the label within its allocation. See the xalign property for that.
Default value: :left

label

The label property of type :string (Read / Write)
The text of the label.
Default value: ""

lines

The lines property of type :int (Read / Write)
The number of lines to which an ellipsized, wrapping label should be limited. This property has no effect if the label is not wrapping or ellipsized. Set this property to -1 if you do not want to limit the number of lines.
Allowed values: >= -1
Default value: -1

max-width-chars

The max-width-chars property of type :int (Read / Write)
The desired maximum width of the label, in characters. If this property is set to -1, the width will be calculated automatically. See the section on text layout for details of how the width-chars and max-width-chars properties determine the width of ellipsized and wrapped labels.
Allowed values: >= -1
Default value: -1

mnemonic-keyval

The mnemonic-keyval property of :uint (Read)
The mnemonic accelerator key for this label.
Default value: #xffffff

The mnemonic-widget property of type gtk-widget (Read / Write)
The widget to be activated when the mnemonic key of the label is pressed.

pattern

The pattern property of type :string (Write)
A string with "_" characters in positions correspond to characters in the text to underline.
Default value: nil

selectable

The selectable property of type :boolean (Read / Write)
Whether the label text can be selected with the mouse.
Default value: false

selection-bound

The selection-bound property of type :int (Read)
The position of the opposite end of the selection from the cursor in chars.
Allowed values: >= 0
Default value: 0

single-line-mode

The single-line-mode property of type :boolean (Read / Write)
Whether the label is in single line mode. In single line mode, the height of the label does not depend on the actual text, it is always set to the (ascent + descent) value of the font. This can be an advantage in situations where resizing the label because of text changes would be distracting, e.g. in a statusbar.
Default value: false

track-visited-links

The track-visited-links property of type :boolean (Read / Write)
Set this property to true to make the label track which links have been clicked. It will then apply the color of the visited-link-color style property of a gtk-widget object, instead of the color of the link-color style property.
Default value: true

use-markup

The use-markup property of type :boolean (Read / Write)
The text of the label includes XML Pango markup.
Default value: false

use-underline

The use-underline property of type :boolean (Read / Write)
If set, an underline in the text indicates the next character should be used for the mnemonic accelerator key.
Default value: false

width-chars

The width-chars property of :int (Read / Write)
The desired width of the label, in characters. If this property is set to -1, the width will be calculated automatically. See the section on text layout for details of how the width-chars and max-width-chars properties determine the width of ellipsized and wrapped labels.
Allowed values: >= -1
Default value: -1

wrap

The wrap property of type :boolean (Read / Write)
If set, wrap lines if the text becomes too wide.
Default value: false

wrap-mode

The wrap-mode property of type pango-wrap-mode (Read / Write)
If line wrapping is on, see the wrap property, this controls how the line wrapping is done. The default is :word, which means wrap on word boundaries.
Default value: :word

xalign

The xalign property of type :float (Read / Write)
Determines the horizontal aligment of the label text inside the labels size allocation. Compare this to the halign property, which determines how the labels size allocation is positioned in the space available for the label.
Allowed values: [0,1]
Default value: 0.5

yalign

The yalign property of type :float (Read / Write)
Determines the vertical aligment of the label text inside the labels size allocation. Compare this to valign, which determines how the labels size allocation is positioned in the space available for the label.
Allowed values: [0,1]
Default value: 0.5

Details

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, a gtk-menu-item, or a gtk-combo-box widget.

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 ((button (make-instance 'gtk-button)))
   (gtk-container-add button
                      (gtk-label-new-with-mneonic "_Hello"))
   ... )

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 entry with the gtk-label-mnemonic-widget function:

;; Pressing Alt+H will focus the entry
(let ((entry (make-instance 'gtk-entry))
      (label (gtk-label-new-with-mnemonic "_Hello")))
   (gtk-label-mnemonic-widget 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 is how to create a label with a small font:

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

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 slot access 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, 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 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 slot access 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-line-wrap function.

The gtk-label-justify slot access 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, 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 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 the <span style="color: red">
                                   <a>GTK website</a></span> for more...")

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

GtkLabel as GtkBuildable

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 this 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.

CSS nodes

 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.

Signal Details

The "activate-current-link" signal

 lambda (label)    :action

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.

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

The "activate-link" signal

 lambda (label uri)    :run-last

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.

label: The gtk-label widget on which the signal was emitted.
uri: A string with the URI that is activated.
Returns: True if the link has been activated.

The "copy-clipboard" signal

 lambda (label)    :action

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.

label: The gtk-label widget which received the signal.

The "move-cursor" signal

 lambda (label step count extend)    :action

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.

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: An integer with the number of step units to move.
extend: True if the move should extend the selection.

The "populate-popup" signal

 lambda (label menu)    :run-last

The signal gets emitted before showing the context menu of the label. Note that only selectable labels have context menus. If you need to add items to the context menu, connect to this signal and append your menuitems to the menu.

label: The gtk-label widget on which the signal is emitted.
menu: The gtk-menu widget that is being populated.