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Adjustment

The invisible Adjustment object provides a store for values used with widgets such as the :doc:`spinbutton`, :doc:`scale`, :doc:`scalebutton` or :doc:`scrollbar`. It provides options to configure the minimum and maximum allowable values and increments.

Constructor

The construction method for the Adjustment is:

GtkWidget *adjustment = gtk_adjustment_new(value, lower, upper, step_increment, page_increment, page_size);

The value is the initial number which the Adjustment starts with. The lower and upper values are the limits which the Adjustment allows. A step_increment is the standard number which the value is adjusted by whereas the page_increment value is the major number to adjust by. The page_size is only used by some widgets and determines the viewable area. In most cases, this will be set to 0 as it is not required.

Methods

The value held by the Adjustment can be set using the method:

gtk_adjustment_set_value(GTK_ADJUSTMENT(adjustment), value);

Retrieval of the value from the Adjustment is made using:

gtk_adjustment_get_value(GTK_ADJUSTMENT(adjustment));

The value defined at construction can also be set or changed while running with the methods:

gtk_adjustment_set_lower(GTK_ADJUSTMENT(adjustment), lower);
gtk_adjustment_set_upper(GTK_ADJUSTMENT(adjustment), upper);
gtk_adjustment_set_step_increment(GTK_ADJUSTMENT(adjustment), step_increment);
gtk_adjustment_set_page_increment(GTK_ADJUSTMENT(adjustment), page_increment);
gtk_adjustment_set_page_size(GTK_ADJUSTMENT(adjustment), page_size);

If required, the Adjustment settings can also be fetched individually with:

gtk_adjustment_get_lower(GTK_ADJUSTMENT(adjustment));
gtk_adjustment_get_upper(GTK_ADJUSTMENT(adjustment));
gtk_adjustment_get_step_increment(GTK_ADJUSTMENT(adjustment));
gtk_adjustment_get_page_increment(GTK_ADJUSTMENT(adjustment));
gtk_adjustment_get_page_size(GTK_ADJUSTMENT(adjustment));

Values on the Adjustment can also be changed using a single method. This prevents multiple calls of the "changed" signal. The values are set using:

gtk_adjustment_configure(GTK_ADJUSTMENT(adjustment), value, lower, upper, step_increment, page_increment, page_size);

Signals

Commonly used signals of the Adjustment object are:

"changed" (adjustment)
"value-changed" (adjustment)

The "changed" signal is emitted from the Adjustment whenever a value other the set value is changed. Alternatively, the "value-changed" signal only emits when the set value is changed.

Example

An example of an Adjustment in use can be seen with other widgets such as SpinButton, Scale, ScaleButton, or Scrollbar.