## GtkScale

GtkScale — Base class for GtkHScale and GtkVScale

## Synopsis

    #include <gtk/gtk.h>

    struct              GtkScale;
    void                gtk_scale_set_digits                (GtkScale *scale,
                                                             gint digits);
    void                gtk_scale_set_draw_value            (GtkScale *scale,
                                                             gboolean draw_value);
    void                gtk_scale_set_value_pos             (GtkScale *scale,
                                                             GtkPositionType pos);
    gint                gtk_scale_get_digits                (GtkScale *scale);
    gboolean            gtk_scale_get_draw_value            (GtkScale *scale);
    GtkPositionType     gtk_scale_get_value_pos             (GtkScale *scale);
    PangoLayout *       gtk_scale_get_layout                (GtkScale *scale);
    void                gtk_scale_get_layout_offsets        (GtkScale *scale,
                                                             gint *x,
                                                             gint *y);
    void                gtk_scale_add_mark                  (GtkScale *scale,
                                                             gdouble value,
                                                             GtkPositionType position,
                                                             const gchar *markup);
    void                gtk_scale_clear_marks               (GtkScale *scale);

## Object Hierarchy

      GObject
       +----GInitiallyUnowned
             +----GtkObject
                   +----GtkWidget
                         +----GtkRange
                               +----GtkScale
                                     +----GtkHScale
                                     +----GtkVScale

## Implemented Interfaces

GtkScale implements AtkImplementorIface, GtkBuildable and GtkOrientable.

## Properties

      "digits"                   gint                  : Read / Write
      "draw-value"               gboolean              : Read / Write
      "value-pos"                GtkPositionType       : Read / Write

## Style Properties

      "slider-length"            gint                  : Read
      "value-spacing"            gint                  : Read

## Signals

      "format-value"                                   : Run Last

## Description

A GtkScale is a slider control used to select a numeric value. To use it, you'll probably want to investigate the methods on its base class, GtkRange, in addition to the methods for GtkScale itself. To set the value of a scale, you would normally use `gtk_range_set_value()`. To detect changes to the value, you would normally use the "value_changed" signal.

The GtkScale widget is an abstract class, used only for deriving the subclasses GtkHScale and GtkVScale. To create a scale widget, call `gtk_hscale_new_with_range()` or `gtk_vscale_new_with_range()`.

### GtkScale as GtkBuildable

GtkScale supports a custom <marks> element, which can contain multiple <mark> elements. The "value" and "position" attributes have the same meaning as `gtk_scale_add_mark()` parameters of the same name. If the element is not empty, its content is taken as the markup to show at the mark. It can be translated with the usual "translatable and "context" attributes.

## Details

### struct GtkScale

    struct GtkScale;

The fields of the GtkScale struct should only be accessed via the accessor functions.

### gtk_scale_set_digits ()

    void                gtk_scale_set_digits                (GtkScale *scale,
                                                             gint digits);

Sets the number of decimal places that are displayed in the value. Also causes the value of the adjustment to be rounded off to this number of digits, so the retrieved value matches the value the user saw.

`scale` : | a GtkScale
`digits` : | the number of decimal places to display, e.g. use 1 to display 1.0, 2 to display 1.00, etc

### gtk_scale_set_draw_value ()

    void                gtk_scale_set_draw_value            (GtkScale *scale,
                                                             gboolean draw_value);

Specifies whether the current value is displayed as a string next to the slider.

`scale` : | a GtkScale
`draw_value` : | `TRUE` to draw the value

### gtk_scale_set_value_pos ()

    void                gtk_scale_set_value_pos             (GtkScale *scale,
                                                             GtkPositionType pos);

Sets the position in which the current value is displayed.

`scale` : | a GtkScale
`pos` : | the position in which the current value is displayed

### gtk_scale_get_digits ()

    gint                gtk_scale_get_digits                (GtkScale *scale);

Gets the number of decimal places that are displayed in the value.

`scale` : | a GtkScale
Returns : | the number of decimal places that are displayed

### gtk_scale_get_draw_value ()

    gboolean            gtk_scale_get_draw_value            (GtkScale *scale);

Returns whether the current value is displayed as a string next to the slider.

`scale` : | a GtkScale
Returns : | whether the current value is displayed as a string

### gtk_scale_get_value_pos ()

    GtkPositionType     gtk_scale_get_value_pos             (GtkScale *scale);

Gets the position in which the current value is displayed.

`scale` : | a GtkScale
Returns : | the position in which the current value is displayed

### gtk_scale_get_layout ()

    PangoLayout *       gtk_scale_get_layout                (GtkScale *scale);

Gets the PangoLayout used to display the scale. The returned object is owned by the scale so does not need to be freed by the caller.

`scale` : | A GtkScale
Returns : | the PangoLayout for this scale, or `NULL` if the "draw-value" property is `FALSE`. [transfer none]

Since 2.4

### gtk_scale_get_layout_offsets ()

    void                gtk_scale_get_layout_offsets        (GtkScale *scale,
                                                             gint *x,
                                                             gint *y);

Obtains the coordinates where the scale will draw the PangoLayout representing the text in the scale. Remember when using the PangoLayout function you need to convert to and from pixels using `PANGO_PIXELS()` or PANGO_SCALE.

If the "draw-value" property is `FALSE`, the return values are undefined.

`scale` : | a GtkScale
`x` : | location to store X offset of layout, or `NULL`. [out][allow-none]
`y` : | location to store Y offset of layout, or `NULL`. [out][allow-none]

Since 2.4

### gtk_scale_add_mark ()

    void                gtk_scale_add_mark                  (GtkScale *scale,
                                                             gdouble value,
                                                             GtkPositionType position,
                                                             const gchar *markup);

Adds a mark at `value`.

A mark is indicated visually by drawing a tick mark next to the scale, and GTK+ makes it easy for the user to position the scale exactly at the marks value.

If `markup` is not `NULL`, text is shown next to the tick mark.

To remove marks from a scale, use `gtk_scale_clear_marks()`.

`scale` : | a GtkScale
`value` : | the value at which the mark is placed, must be between the lower and upper limits of the scales' adjustment
`position` : | where to draw the mark. For a horizontal scale, GTK_POS_TOP is drawn above the scale, anything else below. For a vertical scale, GTK_POS_LEFT is drawn to the left of the scale, anything else to the right.
`markup` : | Text to be shown at the mark, using Pango markup, or `NULL`. [allow-none]

Since 2.16

### gtk_scale_clear_marks ()

    void                gtk_scale_clear_marks               (GtkScale *scale);

Removes any marks that have been added with `gtk_scale_add_mark()`.

`scale` : | a GtkScale

Since 2.16

## Property Details

### The `"digits"` property

      "digits"                   gint                  : Read / Write

The number of decimal places that are displayed in the value.

Allowed values: [-1,64]

Default value: 1

### The `"draw-value"` property

      "draw-value"               gboolean              : Read / Write

Whether the current value is displayed as a string next to the slider.

Default value: TRUE

### The `"value-pos"` property

      "value-pos"                GtkPositionType       : Read / Write

The position in which the current value is displayed.

Default value: GTK_POS_TOP

## Style Property Details

### The `"slider-length"` style property

      "slider-length"            gint                  : Read

Length of scale's slider.

Allowed values: >= 0

Default value: 31

### The `"value-spacing"` style property

      "value-spacing"            gint                  : Read

Space between value text and the slider/trough area.

Allowed values: >= 0

Default value: 2

## Signal Details

### The `"format-value"` signal

    gchar*              user_function                      (GtkScale *scale,
                                                            gdouble   value,
                                                            gpointer  user_data)      : Run Last

Signal which allows you to change how the scale value is displayed. Connect a signal handler which returns an allocated string representing `value`. That string will then be used to display the scale's value.

Here's an example signal handler which displays a value 1.0 as with "-->1.0<--".

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    static gchar*
    format_value_callback (GtkScale *scale,
                           gdouble   value)
    {
      return g_strdup_printf ("-->%0.*g<--",
                              gtk_scale_get_digits (scale), value);
     }

`scale` : | the object which received the signal
`value` : | the value to format
`user_data` : | user data set when the signal handler was connected.
Returns : | allocated string representing `value`