Gtk Simple Widgets

These are widgets that can be clicked or otherwise react to a user's request. Gtk provides many different types of widgets, and only some are illustrated here. Also, within each widget type, only a small amount of the supported behaviour is shown

Buttons

A button displays some text and/or icon, and generates a 'clicked' signal when clicked by the user. The simplest way to create a button is to pass it some text to use as the label:

button1 = Button("Click me")

An alternative way is to use one of the stock actions (see  here for a complete list). For example:

button1 = Button(Stock.quit)

To connect a method to a button, listen to the 'clicked' event. For example:

listen button1.clicked, ref .buttonClicked

Below is a complete program to create and pack two buttons into a window. When the top button is clicked, a message is printed on the terminal, and when the bottom button is clicked, the application quits. The window should look something like:

# @args -pkg:gtk-sharp-2.0  # remove initial '#'

use Gtk

class ExampleWindow inherits Window
    cue init
        base.init("Buttons Example")
        .setDefaultSize(300,200)
        listen .deleteEvent, ref .quit
        .createWidgets

    def quit(obj, e)
        Application.quit

    def createWidgets
        # Create a button with given title text
        button1 = Button("Click me")
        # associate action when clicked
        listen button1.clicked, ref .buttonClicked

        # Create a button using stock 'quit' label and icon
        button2 = Button(Stock.quit)
        # associate action when clicked
        listen button2.clicked, ref .quit

        # Add the two buttons to the window within a box
        box = VBox(true, 0)
        box.packStart(button1, false, false, 20)
        box.packStart(button2, false, false, 20)

        .add(box)

    def buttonClicked(obj, e)
        print "Clicked button"

class MainProgram
    def main
        Application.init
        window = ExampleWindow()
        window.showAll
        Application.run

Check Buttons

A check button has a label and a tick box; clicking on the button will tick or untick the box. The checkbutton's state is stored in its attribute 'active'. An example of a check button:

(To use this code, replace the 'createWidgets' method in the above example, and add the field definition.)

    var _checkbutton as CheckButton # store the check button as a field

    def createWidgets
        _checkbutton = CheckButton("select") # create the check button

        # Create a button to print out state of other widgets
        button = Button("Show State")
        # associate action when clicked
        listen button.clicked, ref .showState

        # Add the two buttons to the window within a box
        box = VBox(true, 0)
        box.packStart(_checkbutton, false, false, 20)
        box.packStart(button, false, false, 20)

        .add(box)

    def showState(obj, e)
        print "Check button state is", _checkbutton.active # report the check button's state

Radio Buttons

Combo Boxes

Spin Buttons

A spin button is used to select a number from within a numeric range. The user may click on the up/down arrows to the side of the field to change the value.

Using a spin button means first creating an instance of the 'Adjustment' class: this holds the min/max values for the range, as well as information on how large a jump the user can make. The 'Adjustment' class takes 6 float parameters:

• the initial value
• the minimum value
• the maximum value
• the increment for a single step (e.g. one click on an arrow)
• the increment for a page-up or page-down keypress
• page size (but cobra tells me using any value other than 0 for this parameter is deprecated)

The spin button takes three parameters:

• an instance of the 'Adjustment' class
• the 'climb rate', which affects the acceleration when you hold a button down
• the number of decimal places to show

The 'value' attribute of the spin button is used to retrieve the current value.

To create a spin box which covers the numbers 0 to 100, and produces integer values:

        model = Adjustment(50.0f, 0.0f, 100.0f, 1.0f, 10.0f, 0f)
        _spinbutton = SpinButton(model, 1.0f, 0)

To create a spin box which covers a floating point range -10.000 to 10.000, producing float values at intervals of 0.001:

        model = Adjustment(0.0f, -10.0f, 10.0f, 0.001f, 1.0f, 0f)
        _spinbutton = SpinButton(model, 1.0f, 3)
        _spinbutton.snapToTicks = true # used to round entries such as 1.2341 to 1.234