GtkAdjustment
3
GTK Library

# 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);
    void                gtk_adjustment_configure            (GtkAdjustment *adjustment,
                                                             gdouble value,
                                                             gdouble lower,
                                                             gdouble upper,
                                                             gdouble step_increment,
                                                             gdouble page_increment,
                                                             gdouble page_size);
    gdouble             gtk_adjustment_get_lower            (GtkAdjustment *adjustment);
    gdouble             gtk_adjustment_get_page_increment   (GtkAdjustment *adjustment);
    gdouble             gtk_adjustment_get_page_size        (GtkAdjustment *adjustment);
    gdouble             gtk_adjustment_get_step_increment   (GtkAdjustment *adjustment);
    gdouble             gtk_adjustment_get_upper            (GtkAdjustment *adjustment);
    void                gtk_adjustment_set_lower            (GtkAdjustment *adjustment,
                                                             gdouble lower);
    void                gtk_adjustment_set_page_increment   (GtkAdjustment *adjustment,
                                                             gdouble page_increment);
    void                gtk_adjustment_set_page_size        (GtkAdjustment *adjustment,
                                                             gdouble page_size);
    void                gtk_adjustment_set_step_increment   (GtkAdjustment *adjustment,
                                                             gdouble step_increment);
    void                gtk_adjustment_set_upper            (GtkAdjustment *adjustment,
                                                             gdouble upper);

## Object Hierarchy

      GObject
       +----GInitiallyUnowned
             +----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

## Signals

      "changed"                                        : Run First / No Recursion
      "value-changed"                                  : Run First / No Recursion

## 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 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` :

  a GtkAdjustment

### 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` :

  a GtkAdjustment

### gtk_adjustment_configure ()

    void                gtk_adjustment_configure            (GtkAdjustment *adjustment,
                                                             gdouble value,
                                                             gdouble lower,
                                                             gdouble upper,
                                                             gdouble step_increment,
                                                             gdouble page_increment,
                                                             gdouble page_size);

Sets all properties of the adjustment at once.

Use this function to avoid multiple emissions of the "changed" signal. See `gtk_adjustment_set_lower()` for an alternative way of compressing multiple emissions of "changed" into one.

`adjustment` :

  a GtkAdjustment

`value` :

  the new value

`lower` :

  the new minimum value

`upper` :

  the new maximum value

`step_increment` :

  the new step increment

`page_increment` :

  the new page increment

`page_size` :

  the new page size

Since 2.14

### gtk_adjustment_get_lower ()

    gdouble             gtk_adjustment_get_lower            (GtkAdjustment *adjustment);

Retrieves the minimum value of the adjustment.

`adjustment` :

  a GtkAdjustment

Returns :

  The current minimum value of the adjustment.

Since 2.14

### gtk_adjustment_get_page_increment ()

    gdouble             gtk_adjustment_get_page_increment   (GtkAdjustment *adjustment);

Retrieves the page increment of the adjustment.

`adjustment` :

  a GtkAdjustment

Returns :

  The current page increment of the adjustment.

Since 2.14

### gtk_adjustment_get_page_size ()

    gdouble             gtk_adjustment_get_page_size        (GtkAdjustment *adjustment);

Retrieves the page size of the adjustment.

`adjustment` :

  a GtkAdjustment

Returns :

  The current page size of the adjustment.

Since 2.14

### gtk_adjustment_get_step_increment ()

    gdouble             gtk_adjustment_get_step_increment   (GtkAdjustment *adjustment);

Retrieves the step increment of the adjustment.

`adjustment` :

  a GtkAdjustment

Returns :

  The current step increment of the adjustment.

Since 2.14

### gtk_adjustment_get_upper ()

    gdouble             gtk_adjustment_get_upper            (GtkAdjustment *adjustment);

Retrieves the maximum value of the adjustment.

`adjustment` :

  a GtkAdjustment

Returns :

  The current maximum value of the adjustment.

Since 2.14

### gtk_adjustment_set_lower ()

    void                gtk_adjustment_set_lower            (GtkAdjustment *adjustment,
                                                             gdouble lower);

Sets the minimum value of the adjustment.

When setting multiple adjustment properties via their individual setters, multiple "changed" signals will be emitted. However, since the emission of the "changed" signal is tied to the emission of the "GObject::notify" signals of the changed properties, it's possible to compress the "changed" signals into one by calling `g_object_freeze_notify()` and `g_object_thaw_notify()` around the calls to the individual setters.

Alternatively, using a single `g_object_set()` for all the properties to change, or using `gtk_adjustment_configure()` has the same effect of compressing "changed" emissions.

`adjustment` :

  a GtkAdjustment

`lower` :

  the new minimum value

Since 2.14

### gtk_adjustment_set_page_increment ()

    void                gtk_adjustment_set_page_increment   (GtkAdjustment *adjustment,
                                                             gdouble page_increment);

Sets the page increment of the adjustment.

See `gtk_adjustment_set_lower()` about how to compress multiple emissions of the "changed" signal when setting multiple adjustment properties.

`adjustment` :

  a GtkAdjustment

`page_increment` :

  the new page increment

Since 2.14

### gtk_adjustment_set_page_size ()

    void                gtk_adjustment_set_page_size        (GtkAdjustment *adjustment,
                                                             gdouble page_size);

Sets the page size of the adjustment.

See `gtk_adjustment_set_lower()` about how to compress multiple emissions of the "changed" signal when setting multiple adjustment properties.

`adjustment` :

  a GtkAdjustment

`page_size` :

  the new page size

Since 2.14

### gtk_adjustment_set_step_increment ()

    void                gtk_adjustment_set_step_increment   (GtkAdjustment *adjustment,
                                                             gdouble step_increment);

Sets the step increment of the adjustment.

See `gtk_adjustment_set_lower()` about how to compress multiple emissions of the "changed" signal when setting multiple adjustment properties.

`adjustment` :

  a GtkAdjustment

`step_increment` :

  the new step increment

Since 2.14

### gtk_adjustment_set_upper ()

    void                gtk_adjustment_set_upper            (GtkAdjustment *adjustment,
                                                             gdouble upper);

Sets the maximum value of the adjustment.

Note that values will be restricted by `upper - page-size` if the page-size property is nonzero.

See `gtk_adjustment_set_lower()` about how to compress multiple emissions of the "changed" signal when setting multiple adjustment properties.

`adjustment` :

  a GtkAdjustment

`upper` :

  the new maximum value

Since 2.14

## Property Details

### The `"lower"` property

      "lower"                    gdouble               : Read / Write

The minimum value of the adjustment.

Default value: 0

Since 2.4

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

      "page-increment"           gdouble               : Read / Write

The page increment of the adjustment.

Default value: 0

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.

Default value: 0

Since 2.4

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

      "step-increment"           gdouble               : Read / Write

The step increment of the adjustment.

Default value: 0

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.

Default value: 0

Since 2.4

### The `"value"` property

      "value"                    gdouble               : Read / Write

The value of the adjustment.

Default value: 0

Since 2.4

## Signal Details

### The `"changed"` signal

    void                user_function                      (GtkAdjustment *adjustment,
                                                            gpointer       user_data)       : Run First / No Recursion

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)       : Run First / No Recursion

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.