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

None

The gtk:level-bar widget is a level bar widget that can be used as a level indicator. Typical use cases are displaying the strength of a password, or showing the charge level of a battery.

Figure: GtkLevelBar

Use the gtk:level-bar-value function to set the current value, and the gtk:level-bar-add-offset-value function to set the value offsets at which the level bar will be considered in a different state. GTK will add a few offsets by default on the level bar: "low", "high" and "full", with values 0.25, 0.75 and 1.0 respectively.

Note that it is your responsibility to update preexisting offsets when changing the minimum or maximum value. GTK will simply clamp them to the new range.

Adding a custom offset on the bar

The default interval of values is between zero and one, but it is possible to modify the interval using the gtk:level-bar-min-value and gtk:level-bar-max-value functions. The value will be always drawn in proportion to the admissible interval, that is, a value of 15 with a specified interval between 10 and 20 is equivalent to a value of 0.5 with an interval between 0 and 1. When the :discrete level bar mode is used, the level bar is rendered as a finite number of separated blocks instead of a single one. The number of blocks that will be rendered is equal to the number of units specified by the admissible interval.

For instance, to build a lever bar rendered with five blocks, it is sufficient to set the minimum value to 0 and the maximum value to 5 after changing the indicator mode to discrete. The gtk:level-bar implementation of the gtk:buildable interface supports a custom <offsets> element, which can contain any number of <offset> elements, each of which must have name and value attributes.

levelbar[.discrete]
╰── trough
    ├── block.filled.level-name
    ┊
    ├── block.empty
    ┊    

The gtk:level-bar implementation has a main CSS node with name levelbar and one of the .discrete or .continuous style classes and a subnode with name trough. Below the trough node are a number of nodes with name block and .filled or .empty style class. In continuous mode, there is exactly one node of each, in discrete mode, the number of filled and unfilled nodes corresponds to blocks that are drawn. The block.filled nodes also get a .level-name style class corresponding to the level for the current value.

In horizontal orientation, the nodes are always arranged from left to right, regardless of text direction. Adding a custom offset on the bar.

(defun create-level-bar (orientation)
  (let* ((levelbar (make-instance 'gtk:level-bar
                                  :orientation orientation)))
    ;; This changes the value of the default low offset
    (gtk:level-bar-add-offset-value levelbar "low" 0.10d0)
    ;; This adds a new offset to the bar. The application will
    ;; be able to change its color CSS like this:
    ;;
    ;; levelbar block.my-offset {
    ;;   background-color: magenta;
    ;;   border-style: solid;
    ;;   border-color: black;
    ;;   border-style: 1px;
    ;; }
    (gtk:level-bar-add-offset-value levelbar "my-offset" 0.60d0)
    ;; Return the new level bar
    levelbar))    

The gtk:level-bar implementation uses the :meter role of the gtk:accessible-role enumeration

The "offset-changed" signal

lambda (levelbar name)    :detailed      

levelbar

The gtk:level-bar widget which received the signal.

name

The string with the name of the offset that changed value.

Emitted when an offset specified on the level bar changes value as an effect to the gtk:level-bar-add-offset-value function being called. The signal supports detailed connections. You can connect to the "changed::x" detailed signal in order to only receive callbacks when the value of "x" offset changes.