## GtkAdjustment

GtkAdjustment — A GtkObject representing an adjustable bounded value

## Synopsis

    #include <gtk/gtk.h>

                GtkAdjustment;
    GtkObject*  gtk_adjustment_new              (gdouble value,
                                                 gdouble lower,
                                                 gdouble upper,
                                                 gdouble step_increment,
                                                 gdouble page_increment,
                                                 gdouble page_size);
    gdouble     gtk_adjustment_get_value        (GtkAdjustment *adjustment);
    void        gtk_adjustment_set_value        (GtkAdjustment *adjustment,
                                                 gdouble value);
    void        gtk_adjustment_clamp_page       (GtkAdjustment *adjustment,
                                                 gdouble lower,
                                                 gdouble upper);
    void        gtk_adjustment_changed          (GtkAdjustment *adjustment);
    void        gtk_adjustment_value_changed    (GtkAdjustment *adjustment);

## Object Hierarchy

      GObject
       +----GtkObject
             +----GtkAdjustment

## Properties

      "lower"                gdouble               : Read / Write
      "page-increment"       gdouble               : Read / Write
      "page-size"            gdouble               : Read / Write
      "step-increment"       gdouble               : Read / Write
      "upper"                gdouble               : Read / Write
      "value"                gdouble               : Read / Write

## Signal Prototypes

    "changed"   void        user_function      (GtkAdjustment *adjustment,
                                                gpointer user_data);
    "value-changed"
                void        user_function      (GtkAdjustment *adjustment,
                                                gpointer user_data);

## Description

The GtkAdjustment 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 GTK+ widgets, including GtkSpinButton, GtkViewport, and GtkRange (which is a base class for GtkHScrollbar, GtkVScrollbar, GtkHScale, and GtkVScale).

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

The owner of the GtkAdjustment 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.

## Details

### GtkAdjustment

    typedef struct _GtkAdjustment GtkAdjustment;

The GtkAdjustment-struct struct contains the following fields.

gdouble lower; | the minimum value.
gdouble upper; | the maximum value.
gdouble value; | the current value.
gdouble step_increment; | the increment to use to make minor changes to the value. In a GtkScrollbar 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.
gdouble page_increment; | the increment to use to make major changes to the value. In a GtkScrollbar this increment is used when the mouse is clicked in the trough, to scroll by a large amount.
gdouble page_size; | the page size. In a GtkScrollbar this is the size of the area which is currently visible.

### gtk_adjustment_new ()

    GtkObject*  gtk_adjustment_new              (gdouble value,
                                                 gdouble lower,
                                                 gdouble upper,
                                                 gdouble step_increment,
                                                 gdouble page_increment,
                                                 gdouble page_size);

Creates a new GtkAdjustment.

`value` : | the initial value.
`lower` : | the minimum value.
`upper` : | the maximum value.
`step_increment` : | the step increment.
`page_increment` : | the page increment.
`page_size` : | the page size.
Returns : | a new GtkAdjustment.

### gtk_adjustment_get_value ()

    gdouble     gtk_adjustment_get_value        (GtkAdjustment *adjustment);

Gets the current value of the adjustment. See `gtk_adjustment_set_value()`.

`adjustment` : | a GtkAdjustment
Returns : | The current value of the adjustment.

### gtk_adjustment_set_value ()

    void        gtk_adjustment_set_value        (GtkAdjustment *adjustment,
                                                 gdouble value);

Sets the GtkAdjustment value. The value is clamped to lie between `adjustment->lower` and `adjustment->upper`.

Note that for adjustments which are used in a GtkScrollbar, the effective range of allowed values goes from `adjustment->lower` to `adjustment->upper - adjustment->page_size`.

`adjustment` : | a GtkAdjustment.
`value` : | the new value.

### gtk_adjustment_clamp_page ()

    void        gtk_adjustment_clamp_page       (GtkAdjustment *adjustment,
                                                 gdouble lower,
                                                 gdouble upper);

Updates the GtkAdjustment `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.

`adjustment` : | a GtkAdjustment.
`lower` : | the lower value.
`upper` : | the upper value.

### gtk_adjustment_changed ()

    void        gtk_adjustment_changed          (GtkAdjustment *adjustment);

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

`adjustment` : |

### gtk_adjustment_value_changed ()

    void        gtk_adjustment_value_changed    (GtkAdjustment *adjustment);

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

`adjustment` : |

## Properties

### The "`lower`" property

      "lower"                gdouble               : Read / Write

The minimum value of the adjustment.

Since 2.4

### The "`page-increment`" property

      "page-increment"       gdouble               : Read / Write

The page increment of the adjustment.

Since 2.4

### The "`page-size`" property

      "page-size"            gdouble               : 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 GtkSpinButton.

Since 2.4

### The "`step-increment`" property

      "step-increment"       gdouble               : Read / Write

The step increment of the adjustment.

Since 2.4

### The "`upper`" property

      "upper"                gdouble               : Read / Write

The maximum value of the adjustment. Note that values will be restricted by `upper - page-size` if the page-size property is nonzero.

Since 2.4

### The "`value`" property

      "value"                gdouble               : Read / Write

The value of the adjustment.

Since 2.4

## Signals

### The "changed" signal

    void        user_function                  (GtkAdjustment *adjustment,
                                                gpointer user_data);

Emitted when one or more of the GtkAdjustment fields have been changed, other than the value field.

`adjustment` : | the object which received the signal.
`user_data` : | user data set when the signal handler was connected.

### The "value-changed" signal

    void        user_function                  (GtkAdjustment *adjustment,
                                                gpointer user_data);

Emitted when the GtkAdjustment value field has been changed.

`adjustment` : | the object which received the signal.
`user_data` : | user data set when the signal handler was connected.