GtkScale: GTK+ 3 Reference Manual

## GtkScale GtkScale — A slider widget for selecting a value from a range |

## Functions

GtkWidget * | gtk_scale_new ()
GtkWidget * | gtk_scale_new_with_range ()
void | gtk_scale_set_digits ()
void | gtk_scale_set_draw_value ()
void | gtk_scale_set_has_origin ()
void | gtk_scale_set_value_pos ()
gint | gtk_scale_get_digits ()
gboolean | gtk_scale_get_draw_value ()
gboolean | gtk_scale_get_has_origin ()
GtkPositionType | gtk_scale_get_value_pos ()
PangoLayout * | gtk_scale_get_layout ()
void | gtk_scale_get_layout_offsets ()
void | gtk_scale_add_mark ()
void | gtk_scale_clear_marks ()

## Properties

int | digits | Read / Write
gboolean | draw-value | Read / Write
gboolean | has-origin | Read / Write
GtkPositionType | value-pos | Read / Write

## Style Properties

int | slider-length | Read
int | value-spacing | Read

## Signals

char* | format-value | Run Last

## Types and Values

struct | GtkScale

## Object Hierarchy

        GObject
        ╰── GInitiallyUnowned
            ╰── GtkWidget
                ╰── GtkRange
                    ╰── GtkScale
                        ├── GtkHScale
                        ╰── GtkVScale

## Implemented Interfaces

GtkScale implements AtkImplementorIface, GtkBuildable and GtkOrientable.

## Includes

    #include <gtk/gtk.h>

## 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.

Note that using the same upper and lower bounds for the GtkScale (through the GtkRange methods) will hide the slider itself. This is useful for applications that want to show an undeterminate value on the scale, without changing the layout of the application (such as movie or music players).

### 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.

### CSS nodes

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    scale[.fine-tune][.marks-before][.marks-after]
    ├── marks.top
    │   ├── mark
    │   ┊    ├── [label]
    │   ┊    ╰── indicator
    ┊   ┊
    │   ╰── mark
    ├── [value]
    ├── contents
    │   ╰── trough
    │       ├── slider
    │       ├── [highlight]
    │       ╰── [fill]
    ╰── marks.bottom
        ├── mark
        ┊    ├── indicator
        ┊    ╰── [label]
        ╰── mark

GtkScale has a main CSS node with name scale and a subnode for its contents, with subnodes named trough and slider.

The main node gets the style class .fine-tune added when the scale is in 'fine-tuning' mode.

If the scale has an origin (see `gtk_scale_set_has_origin()`), there is a subnode with name highlight below the trough node that is used for rendering the highlighted part of the trough.

If the scale is showing a fill level (see `gtk_range_set_show_fill_level()`), there is a subnode with name fill below the trough node that is used for rendering the filled in part of the trough.

If marks are present, there is a marks subnode before or after the contents node, below which each mark gets a node with name mark. The marks nodes get either the .top or .bottom style class.

The mark node has a subnode named indicator. If the mark has text, it also has a subnode named label. When the mark is either above or left of the scale, the label subnode is the first when present. Otherwise, the indicator subnode is the first.

The main CSS node gets the 'marks-before' and/or 'marks-after' style classes added depending on what marks are present.

If the scale is displaying the value (see “draw-value”), there is subnode with name value.

## Functions

### gtk_scale_new ()

    GtkWidget *
    gtk_scale_new (GtkOrientation orientation,
                   GtkAdjustment *adjustment);

Creates a new GtkScale.

#### Parameters

orientation | the scale’s orientation. |
adjustment | the GtkAdjustment which sets the range of the scale, or `NULL` to create a new adjustment. | [nullable]

#### Returns

a new GtkScale

Since: 3.0

### gtk_scale_new_with_range ()

    GtkWidget *
    gtk_scale_new_with_range (GtkOrientation orientation,
                              gdouble min,
                              gdouble max,
                              gdouble step);

Creates a new scale widget with the given orientation that lets the user input a number between `min` and `max` (including `min` and `max` ) with the increment `step` . `step` must be nonzero; it’s the distance the slider moves when using the arrow keys to adjust the scale value.

Note that the way in which the precision is derived works best if `step` is a power of ten. If the resulting precision is not suitable for your needs, use `gtk_scale_set_digits()` to correct it.

#### Parameters

orientation | the scale’s orientation. |
min | minimum value |
max | maximum value |
step | step increment (tick size) used with keyboard shortcuts |

#### Returns

a new GtkScale

Since: 3.0

### 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 to this number of digits, so the retrieved value matches the displayed one, if “draw-value” is `TRUE` when the value changes. If you want to enforce rounding the value when “draw-value” is `FALSE`, you can set “round-digits” instead.

Note that rounding to a small number of digits can interfere with the smooth autoscrolling that is built into GtkScale. As an alternative, you can use the “format-value” signal to format the displayed value yourself.

#### Parameters

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.

#### Parameters

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

### gtk_scale_set_has_origin ()

    void
    gtk_scale_set_has_origin (GtkScale *scale,
                              gboolean has_origin);

If “has-origin” is set to `TRUE` (the default), the scale will highlight the part of the trough between the origin (bottom or left side) and the current value.

#### Parameters

scale | a GtkScale |
has_origin | `TRUE` if the scale has an origin |

Since: 3.4

### 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.

#### Parameters

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.

#### Parameters

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.

#### Parameters

scale | a GtkScale |

#### Returns

whether the current value is displayed as a string

### gtk_scale_get_has_origin ()

    gboolean
    gtk_scale_get_has_origin (GtkScale *scale);

Returns whether the scale has an origin.

#### Parameters

scale | a GtkScale |

#### Returns

`TRUE` if the scale has an origin.

Since: 3.4

### gtk_scale_get_value_pos ()

    GtkPositionType
    gtk_scale_get_value_pos (GtkScale *scale);

Gets the position in which the current value is displayed.

#### Parameters

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.

#### Parameters

scale | A GtkScale |

#### Returns

the PangoLayout for this scale, or `NULL` if the “draw-value” property is `FALSE`.

[transfer none][nullable]

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.

#### Parameters

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()`.

#### Parameters

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 and `GTK_POS_LEFT` are drawn above the scale, anything else below. For a vertical scale, GTK_POS_LEFT and `GTK_POS_TOP` are 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()`.

#### Parameters

scale | a GtkScale |

Since: 2.16

## Types and Values

### struct GtkScale

    struct GtkScale;

## Property Details

### The `“digits”` property

      “digits”                   int

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

Owner: GtkScale

Flags: Read / Write

Allowed values: [-1,64]

Default value: 1

### The `“draw-value”` property

      “draw-value”               gboolean

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

Owner: GtkScale

Flags: Read / Write

Default value: TRUE

### The `“has-origin”` property

      “has-origin”               gboolean

Whether the scale has an origin.

Owner: GtkScale

Flags: Read / Write

Default value: TRUE

### The `“value-pos”` property

      “value-pos”                GtkPositionType

The position in which the current value is displayed.

Owner: GtkScale

Flags: Read / Write

Default value: GTK_POS_TOP

## Style Property Details

### The `“slider-length”` style property

      “slider-length”            int

Length of scale's slider.

`GtkScale:slider-length` has been deprecated since version 3.20 and should not be used in newly-written code.

Use min-height/min-width CSS properties on the slider element instead. The value of this style property is ignored.

Owner: GtkScale

Flags: Read

Allowed values: >= 0

Default value: 31

### The `“value-spacing”` style property

      “value-spacing”            int

Space between value text and the slider/trough area.

`GtkScale:value-spacing` has been deprecated since version 3.20 and should not be used in newly-written code.

Use min-height/min-width CSS properties on the value element instead. The value of this style property is ignored.

Owner: GtkScale

Flags: Read

Allowed values: >= 0

Default value: 2

## Signal Details

### The `“format-value”` signal

    char*
    user_function (GtkScale *scale,
                   double    value,
                   gpointer  user_data)

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.

If no user-provided handlers are installed, the value will be displayed on its own, rounded according to the value of the “digits” property.

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);
     }

#### Parameters

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`

Flags: Run Last