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= class Gtk::Adjustment

The Gtk::Adjustment object represents a value which has an associated lower and upper bound, together with step and page increments, and a page size. It is used within several Ruby/GTK widgets, including Gtk::SpinButton, Gtk::Viewport, and Gtk::Range (which is a base class for Gtk::HScrollbar, Gtk::VScrollbar, Gtk::HScale, and Gtk::VScale).

The Gtk::Adjustment object does not update the value itself. Instead it is left up to the owner of the Gtk::Adjustment to control the value.

The owner of the Gtk::Adjustment typically calls the Gtk::Adjustment#value_changed and Gtk::Adjustment#changed functions after changing the value and its bounds. This results in the emission of the "value_changed" or "changed" signal respectively.

== Object Hierarchy

* Object
  * GLib::Instantiatable
    * GLib::Object
      * GLib::InitiallyUnowned
        * Gtk::Object
          * Gtk::Adjustment

== Class Methods

--- Gtk::Adjustment.new(value, lower, upper, step_inc, page_inc, page_size)

    Creates a new Gtk::Adjustment. All argument types are Float.
    * value: the initial value.
    * lower: the minimum value.
    * upper: the maximum value.
    * step_increment: the increment to use to make minor changes to the value. In a Gtk::Scrollbar this increment is used when the mouse is clicked on the arrows at the top and bottom of the scrollbar, to scroll by a small amount.  
    * page_increment: the increment to use to make major changes to the value. In a Gtk::Scrollbar this increment is used when the mouse is clicked in the trough, to scroll by a large amount.  
    * page_size: the page size. In a Gtk::Scrollbar this is the size of the area which is currently visible.

== Instance Methods

--- value

    Gets the current value of the adjustment. See Gtk::Adjustment#value=.
    * Returns: The current value of the adjustment

--- value=(value)

    Sets the Gtk::Adjustment value.
    * value : the new value
    * Returns: value

--- set_value

    Same as Gtk::Adjustment#value=.
    * value : the new value
    * Returns: self

--- step_increment(step_increment)

    Gets the step_increment value. See Gtk::Adjustment#step_increment=.
    * Returns: step_increment

--- step_increment=(step_increment)

    Sets the increment to use to make minor changes to the value.
    * step_increment : the new step_increment value.
    * Returns: step_increment

--- set_step_increment(step_increment)

    Same as Gtk::Adjustment#step_increment=.
    * step_increment : the new step_increment value.
    * Returns: self

--- clamp_page

    Updates the Gtk::Adjustment value to ensure that the range between lower and upper is in the current page (i.e. between value and value + page_size). If the range is larger than the page size, then only the start of it will be in the current page. A "changed" signal will be emitted if the value is changed.
    * lower: the lower value.  
    * upper: the upper value.  
    * Returns: self

--- lower

    Gets the minimum value of the adjustment. See Gtk::Adjustment#clamp_page.
    * Returns: The minimum value of the adjustment

--- lower=(lower)

    Sets the  minimum value of the adjustment. ((* Since 2.4 *))
    * lower: The minimum value of the adjustment
    * Returns: lower

--- set_lower(lower)

    Same as Gtk::Adjustment#lower=. ((* Since 2.4 *))
    * lower: The minimum value of the adjustment
    * Returns: self

--- upper

    Gets the maximum value of the adjustment. See Gtk::Adjustment#clamp_page.
    * Returns: The maximum value of the adjustment

--- upper=(upper)

    Sets the  maximum value of the adjustment. ((* Since 2.4 *))
    * upper: The maximum value of the adjustment
    * Returns: upper

--- set_upper(upper)

    Same as Gtk::Adjustment#upper=. ((* Since 2.4 *))
    * upper: The maximum value of the adjustment
    * Returns: self

--- page_increment

    Gets the increment to use to make major changes to the value of the adjustment. See Gtk::Adjustment.new.
    * Returns: The increment to use to make major changes to the value of the adjustment

--- page_increment=(page_increment)

    Sets the increment to use to make major changes to the value of the adjustment.
    * page_increment : the new page_increment value.
    * Returns: page_increment

--- set_page_increment(page_increment)

    Same as Gtk::Adjustment#page_increment=.
    * page_increment : the new page_increment value.
    * Returns: self

--- page_size

    Gets the page size value of the adjustment. See Gtk::Adjustment.new.
    * Returns: The page size value of the adjustment

--- page_size=(page_size)

    Sets the page size value of the adjustment.
    * page_size : the new page_size value.
    * Returns: page_size

--- set_page_size(page_size)

    Same as Gtk::Adjustment#page_size=.
    * page_size : the new page_size value.
    * Returns: self

--- changed

    Emits a "changed" signal from the Gtk::Adjustment. This is typically called by the owner of the Gtk::Adjustment after it has changed any of the Gtk::Adjustment fields other than the value.

--- value_changed

    Emits a "value_changed" signal from the Gtk::Adjustment. This is typically called by the owner of the Gtk::Adjustment after it has changed the Gtk::Adjustment value field.

== Properties

--- lower: Float (Read/Write)

    The minimum value of the adjustment. ((* Since 2.4 *))
    * Default value: 0

--- page-increment: Float (Read/Write)

    The page increment of the adjustment. ((* Since 2.4 *))
    * Default value: 0

--- page-size: Float (Read/Write)

    The page size of the adjustment. Note that the page-size is irrelevant and should be set to zero if the adjustment is used for a simple scalar value, e.g. in a Gtk::SpinButton. ((* Since 2.4 *))
    * Default value: 0

--- step-increment: Float (Read/Write)

    The step increment of the adjustment. ((* Since 2.4 *))
    * Default value: 0

--- upper: Float (Read/Write)

    The maximum value of the adjustment. ((* Since 2.4 *))
    * Default value: 0

--- value: Float (Read/Write)

    The value of the adjustment. ((* Since 2.4 *))
    * Default value: 0

== Signals

--- changed: self (Run first / No recursion)

    Emitted when one or more of the GtkAdjustment fields have been changed, other than the value field.
    * self: Gtk::Adjustment

--- value-changed: self (Run first / No recursion)

    Emitted when the GtkAdjustment value field has been changed.
    * self: Gtk::Adjustment

== See Also

== ChangeLog

* 2006-01-31 Apply GTK+-2.4 methods - ((<Masao>))
* 2005-10-27 Fix typos - ((<Masao>))
* 2003-08-22 Added - ((<Masao>))