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## 7 Properties

You can examine or set the value of a widget by using the widget object that was returned by `widget-create`.

Function: widget-value widget

  Return the current value contained in widget. It is an error to call this function on an uninitialized widget.

Function: widget-value-set widget value

  Set the value contained in widget to value. It is an error to call this function with an invalid value.

Important: You must call `widget-setup` after modifying the value of a widget before the user is allowed to edit the widget again. It is enough to call `widget-setup` once if you modify multiple widgets. This is currently only necessary if the widget contains an editing field, but may be necessary for other widgets in the future.

If your application needs to associate some information with the widget objects, for example a reference to the item being edited, it can be done with `widget-put` and `widget-get`. The property names must begin with a ‘`:`’.

Function: widget-put widget property value

  In widget set property to value. property should be a symbol, while value can be anything.

Function: widget-get widget property

  In widget return the value for property. property should be a symbol, the value is what was last set by `widget-put` for property.

Function: widget-member widget property

  Non-`nil` if widget has a value (even `nil`) for property property.

Occasionally it can be useful to know which kind of widget you have, i.e., the name of the widget type you gave when the widget was created.

Function: widget-type widget

  Return the name of widget, a symbol.

Widgets can be in two states: active, which means they are modifiable by the user, or inactive, which means they cannot be modified by the user. You can query or set the state with the following code:

    ;; Examine if widget is active or not.
    (if (widget-apply widget :active)
        (message "Widget is active.")
      (message "Widget is inactive.")

    ;; Make widget inactive.
    (widget-apply widget :deactivate)

    ;; Make widget active.
    (widget-apply widget :activate)

A widget is inactive if it, or any of its ancestors (found by following the `:parent` link), have been deactivated. To make sure a widget is really active, you must therefore activate both it and all its ancestors.

    (while widget
      (widget-apply widget :activate)
      (setq widget (widget-get widget :parent)))

You can check if a widget has been made inactive by examining the value of the `:inactive` keyword. If this is non-`nil`, the widget itself has been deactivated. This is different from using the `:active` keyword, in that the latter tells you if the widget or any of its ancestors have been deactivated. Do not attempt to set the `:inactive` keyword directly. Use the `:activate` `:deactivate` keywords instead.

Next: Defining New Widgets, Previous: Sexp Types, Up: Top [Contents][Index]