SpinButton
| Chapter 8. Miscellaneous Widgets |

## SpinButton

A `SpinButton` allows the user to select a value from a range of numeric values. It has an `Entry` widget with increment and decrement buttons at the side. Clicking the buttons causes the value to 'spin' up and down across the range of possible values. The `Entry` widget may also be used to enter a value directly.

The value can have an adjustable number of decimal places, and the step size is configurable. `SpinButton`s have an 'auto-repeat' feature as well: holding down the increment or decrement button can optionally cause the value to change more quickly the longer the button is held down.

`SpinButton`s use an Adjustment object to hold information about the range of values. These Adjustment attributes are used by the Spin Button like so:

- `value`: value for the Spin Button

- `lower`: lower range value

- `upper`: upper range value

- `step_increment`: value to increment/decrement when pressing mouse button 1

- `page_increment`: value to increment/decrement when pressing mouse button 2

- `page_size`: unused

Additionally, mouse button 3 can be used to jump directly to the `upper` or `lower` values.

The `SpinButton` can create a default `Adjustment`, which you can access via the `get_adjustment()` method, or you can specify an existing `Adjustment` in the constructor.

### Methods

The number of decimal places can be altered using the `set_digits()` method.

You can set the spinbutton's value using the `set_value()` method, and retrieve it with `get_value()`.

The `spin()` method 'spins' the `SpinButton`, as if its increment or decrement button had been clicked. You need to specify a `Gtk::SpinType` to specify the direction or new position.

To prevent the user from typing non-numeric characters into the entry box, pass `true` to the `set_numeric()` method.

To make the `SpinButton` 'wrap' between its upper and lower bounds, use the `set_wrap()` method.

To force it to snap to the nearest `step_increment`, use `set_snap_to_ticks()`.

Reference

### Example

Here's an example of a `SpinButton` in action:

Figure 8.6. SpinButton

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_checkbutton_snap();
      void on_checkbutton_numeric();
      void on_spinbutton_digits_changed();
      void on_button_close();

      enum enumValueFormats
      {
        VALUE_FORMAT_INT,
        VALUE_FORMAT_FLOAT
      };
      void on_button_getvalue(enumValueFormats display);

      //Child widgets:
      Gtk::Frame m_Frame_NotAccelerated, m_Frame_Accelerated;
      Gtk::Box m_HBox_NotAccelerated, m_HBox_Accelerated,
        m_HBox_Buttons;
      Gtk::Box m_VBox_Main, m_VBox, m_VBox_Day, m_VBox_Month, m_VBox_Year,
        m_VBox_Accelerated, m_VBox_Value, m_VBox_Digits;
      Gtk::Label m_Label_Day, m_Label_Month, m_Label_Year,
        m_Label_Value, m_Label_Digits,
        m_Label_ShowValue;
      Glib::RefPtr<Gtk::Adjustment> m_adjustment_day, m_adjustment_month, m_adjustment_year,
        m_adjustment_value, m_adjustment_digits;
      Gtk::SpinButton m_SpinButton_Day, m_SpinButton_Month, m_SpinButton_Year,
        m_SpinButton_Value, m_SpinButton_Digits;
      Gtk::CheckButton m_CheckButton_Snap, m_CheckButton_Numeric;
      Gtk::Button m_Button_Int, m_Button_Float, m_Button_Close;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>
    #include <cstdio>

    ExampleWindow::ExampleWindow()
    :
      m_Frame_NotAccelerated("Not accelerated"),
      m_Frame_Accelerated("Accelerated"),
      m_VBox_Main(Gtk::Orientation::VERTICAL, 5),
      m_VBox(Gtk::Orientation::VERTICAL),
      m_VBox_Day(Gtk::Orientation::VERTICAL),
      m_VBox_Month(Gtk::Orientation::VERTICAL),
      m_VBox_Year(Gtk::Orientation::VERTICAL),
      m_VBox_Accelerated(Gtk::Orientation::VERTICAL),
      m_VBox_Value(Gtk::Orientation::VERTICAL),
      m_VBox_Digits(Gtk::Orientation::VERTICAL),
      m_Label_Day("Day: ", Gtk::Align::START),
      m_Label_Month("Month: ", Gtk::Align::START),
      m_Label_Year("Year: ", Gtk::Align::START),
      m_Label_Value("Value: ", Gtk::Align::START),
      m_Label_Digits("Digits: ", Gtk::Align::START),
      m_adjustment_day( Gtk::Adjustment::create(1.0, 1.0, 31.0, 1.0, 5.0, 0.0) ),
      m_adjustment_month( Gtk::Adjustment::create(1.0, 1.0, 12.0, 1.0, 5.0, 0.0) ),
      m_adjustment_year( Gtk::Adjustment::create(2012.0, 1.0, 2200.0, 1.0, 100.0, 0.0) ),
      m_adjustment_value( Gtk::Adjustment::create(0.0, -10000.0, 10000.0, 0.5, 100.0, 0.0) ),
      m_adjustment_digits( Gtk::Adjustment::create(2.0, 1.0, 5.0, 1.0, 1.0, 0.0) ),
      m_SpinButton_Day(m_adjustment_day),
      m_SpinButton_Month(m_adjustment_month),
      m_SpinButton_Year(m_adjustment_year),
      m_SpinButton_Value(m_adjustment_value, 1.0, 2),
      m_SpinButton_Digits(m_adjustment_digits),
      m_CheckButton_Snap("Snap to 0.5-ticks"),
      m_CheckButton_Numeric("Numeric only input mode"),
      m_Button_Int("Value as Int"),
      m_Button_Float("Value as Float"),
      m_Button_Close("Close")
    {
      set_title("SpinButton");

      m_VBox_Main.set_margin(10);
      set_child(m_VBox_Main);

      m_VBox_Main.append(m_Frame_NotAccelerated);

      m_VBox.set_margin(5);
      m_Frame_NotAccelerated.set_child(m_VBox);

      /* Day, month, year spinners */

      m_VBox.set_spacing(5);
      m_VBox.append(m_HBox_NotAccelerated);

      m_Label_Day.set_expand();
      m_VBox_Day.append(m_Label_Day);

      m_SpinButton_Day.set_wrap();
      m_SpinButton_Day.set_expand();
      m_VBox_Day.append(m_SpinButton_Day);

      m_HBox_NotAccelerated.set_spacing(5);
      m_HBox_NotAccelerated.append(m_VBox_Day);

      m_Label_Month.set_expand();
      m_VBox_Month.append(m_Label_Month);

      m_SpinButton_Month.set_wrap();
      m_SpinButton_Month.set_expand();
      m_VBox_Month.append(m_SpinButton_Month);

      m_HBox_NotAccelerated.append(m_VBox_Month);

      m_Label_Year.set_expand();
      m_VBox_Year.append(m_Label_Year);

      m_SpinButton_Year.set_wrap();
      m_SpinButton_Year.set_expand();
      m_SpinButton_Year.set_size_request(55, -1);
      m_VBox_Year.append(m_SpinButton_Year);

      m_HBox_NotAccelerated.append(m_VBox_Year);

      //Accelerated:
      m_VBox_Main.append(m_Frame_Accelerated);

      m_VBox_Accelerated.set_margin(5);
      m_Frame_Accelerated.set_child(m_VBox_Accelerated);

      m_VBox_Accelerated.set_spacing(5);
      m_VBox_Accelerated.append(m_HBox_Accelerated);

      m_HBox_Accelerated.append(m_VBox_Value);

      m_Label_Value.set_expand();
      m_VBox_Value.append(m_Label_Value);

      m_SpinButton_Value.set_wrap();
      m_SpinButton_Value.set_expand();
      m_SpinButton_Value.set_size_request(100, -1);
      m_VBox_Value.append(m_SpinButton_Value);

      m_HBox_Accelerated.append(m_VBox_Digits);

      m_VBox_Digits.append(m_Label_Digits);
      m_Label_Digits.set_expand();

      m_SpinButton_Digits.set_wrap();
      m_adjustment_digits->signal_value_changed().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_spinbutton_digits_changed) );

      m_VBox_Digits.append(m_SpinButton_Digits);
      m_SpinButton_Digits.set_expand();

      //CheckButtons:
      m_VBox_Accelerated.append(m_CheckButton_Snap);
      m_CheckButton_Snap.set_expand();
      m_CheckButton_Snap.set_active();
      m_CheckButton_Snap.signal_toggled().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_snap) );

      m_VBox_Accelerated.append(m_CheckButton_Numeric);
      m_CheckButton_Numeric.set_expand();
      m_CheckButton_Numeric.set_active();
      m_CheckButton_Numeric.signal_toggled().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_numeric) );

      //Buttons:
      m_VBox_Accelerated.append(m_HBox_Buttons);

      m_Button_Int.signal_clicked().connect( sigc::bind( sigc::mem_fun(*this,
                      &ExampleWindow::on_button_getvalue), VALUE_FORMAT_INT) );
      m_HBox_Buttons.set_spacing(5);
      m_HBox_Buttons.append(m_Button_Int);
      m_Button_Int.set_expand();

      m_Button_Float.signal_clicked().connect( sigc::bind( sigc::mem_fun(*this,
                      &ExampleWindow::on_button_getvalue), VALUE_FORMAT_FLOAT) );
      m_HBox_Buttons.append(m_Button_Float);
      m_Button_Float.set_expand();

      m_VBox_Accelerated.append(m_Label_ShowValue);
      m_Label_ShowValue.set_expand();
      m_Label_ShowValue.set_text("0");

      //Close button:
      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox_Main.append(m_Button_Close);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_close()
    {
      close();
    }

    void ExampleWindow::on_checkbutton_snap()
    {
      m_SpinButton_Value.set_snap_to_ticks( m_CheckButton_Snap.get_active() );
    }

    void ExampleWindow::on_checkbutton_numeric()
    {
      m_SpinButton_Value.set_numeric( m_CheckButton_Numeric.get_active() );
    }

    void ExampleWindow::on_spinbutton_digits_changed()
    {
      m_SpinButton_Value.set_digits( m_SpinButton_Digits.get_value_as_int() );
    }

    void ExampleWindow::on_button_getvalue(enumValueFormats display)
    {
      gchar buf[32];

      if (display == VALUE_FORMAT_INT)
        sprintf (buf, "%d", m_SpinButton_Value.get_value_as_int());
      else
        sprintf (buf, "%0.*f", m_SpinButton_Value.get_digits(),
                m_SpinButton_Value.get_value());

      m_Label_ShowValue.set_text(buf);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

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