Menus & toolbars

In this part of the Ruby Qt programming tutorial, we will work with menus and toolbar.

A menubar is one of the most visible parts of the GUI application. It is a group of commands located in various menus. While in console applications you had to remember all those arcane commands, here we have most of the commands grouped into logical parts. There are accepted standards that further reduce the amount of time spending to learn a new application. Menus group commands that we can use in an application. Toolbars provide a quick access to the most frequently used commands.

Simple menu

The first example will show a simple menu.

#!/usr/bin/ruby

# ZetCode Ruby Qt tutorial
#
# This program shows a simple
# menu. It has one action, which
# will terminate the program, when
# selected. 
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: November 2012

require 'Qt'


class QtApp < Qt::MainWindow

    def initialize
        super
        
        setWindowTitle "Simple menu"
        
        init_ui
        
        resize 250, 150
        move 300, 300

        show
    end
    
    def init_ui
        quit = Qt::Action.new "&Quit", self

        file = menuBar().addMenu "&File"
        file.addAction quit

        connect(quit, SIGNAL("triggered()"), 
            Qt::Application.instance, SLOT("quit()"))
    end
        
end

app = Qt::Application.new ARGV
QtApp.new
app.exec

We have a menubar, a menu and an action. In order to work with menus, we must inherit from MainWindow widget.

quit = Qt::Action.new "&Quit", self

This code line creates a Action. Each Menu has one or more action objects. Note the ampersand (&) character. It creates a shortcut for the item: Alt+Q. It also underlines the Q character. The shortcut is active, when the file menu is dropped down.

file = menuBar().addMenu "&File"
file.addAction quit

We create a Menu object. The ampersand character creates a shortcut: Alt+F. The consecutive shortcuts Alt+F, Alt+Q quit the application.

connect(quit, SIGNAL("triggered()"), 
    Qt::Application.instance, SLOT("quit()"))

When we select this option from the menu, the application quits.

Simple menu
Figure: Simple menu

Submenu

A submenu is a menu plugged into another menu object. The next example demonstrates this.

#!/usr/bin/ruby

# ZetCode Ruby Qt tutorial
#
# This program creates a
# submenu
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: November 2012

require 'Qt'


class QtApp < Qt::MainWindow

    def initialize
        super
        
        setWindowTitle "Submenu"
        
        init_ui
        
        resize 280, 200
        move 300, 300

        show
    end
    
    def init_ui
        quit = Qt::Action.new "&Quit", self

        file = menuBar().addMenu "&File"
        impm = Qt::Menu.new "Import"

        seeds = Qt::Action.new "Import news feed...", self
        marks = Qt::Action.new "Import bookmarks...", self
        mail = Qt::Action.new "Import mail...", self
        
        impm.addAction seeds
        impm.addAction marks
        impm.addAction mail

        file.addMenu impm
        file.addAction quit

        connect(quit, SIGNAL("triggered()"), 
            Qt::Application.instance, SLOT("quit()"))
    end    
    
end

app = Qt::Application.new ARGV
QtApp.new
app.exec

In the example, we have three options in a submenu of a file menu.

file = menuBar().addMenu "&File"
impm = Qt::Menu.new "Import"

We have two Menu objects. The file menu and the import menu.

seeds = Qt::Action.new "Import news feed...", self
marks = Qt::Action.new "Import bookmarks...", self
mail = Qt::Action.new "Import mail...", self

We create three action objects.

impm.addAction seeds
impm.addAction marks
impm.addAction mail

We add the action objects into the import menu.

file.addMenu impm

Finally, we add the import menu into the file menu.

Submenu
Figure: Submenu

Images, menus, separators

In the following example, we will further enhance our previous application. We will add icons to the menus, use shortcuts and a separator. Note that the Gnome desktop might be configured not to display menu icons by default. In such a case we need to enable the menu_have_icons option in the Gnome interface configuration.

gconftool-2 --type Boolean --set /desktop/gnome/interface/menus_have_icons True

We can use the above command or the gconf-editor tool.

#!/usr/bin/ruby

# ZetCode Ruby Qt tutorial
#
# This program shows image
# menus, shortcuts and a separator
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: November 2012

require 'Qt'


class QtApp < Qt::MainWindow

    def initialize
        super
        
        setWindowTitle "Image menu"
        
        init_ui
        
        resize 280, 200
        move 300, 300

        show
    end
    
    def init_ui
        newpix = Qt::Icon.new "new.png"
        openpix = Qt::Icon.new "open.png"
        quitpix = Qt::Icon.new "exit.png"

        newa = Qt::Action.new newpix, "&New", self
        open = Qt::Action.new openpix, "&Open", self
        quit = Qt::Action.new quitpix, "&Quit", self
        quit.setShortcut "Ctrl+Q"
        
        file = menuBar().addMenu "&File"
        file.addAction newa
        file.addAction open
        file.addSeparator
        file.addAction quit

        connect(quit, SIGNAL("triggered()"), 
            Qt::Application.instance, SLOT("quit()"))
    end    
    
end

app = Qt::Application.new ARGV
QtApp.new
app.exec

In our example, we have one menu with three actions. Only the quit action will actually do something if we select it. We also create a separator and a Ctrl+Q shortcut, which will terminate the application.

newpix = Qt::Icon.new "new.png"
openpix = Qt::Icon.new "open.png"
quitpix = Qt::Icon.new "exit.png"

These are PNG images that we will use in the application.

newa = Qt::Action.new newpix, "&New", self
open = Qt::Action.new openpix, "&Open", self
quit = Qt::Action.new quitpix, "&Quit", self

Here we create three action objects. The first parameter is the Icon.

quit.setShortcut "Ctrl+Q"

This line creates a shortcut. By pressing this shortcut, we will run the quit action, which will quit the application.

file.addSeparator

We create a separator. The separator is a horizontal line, which enables us to group menu actions into some logical parts.

Images, shortcut and a separator
Figure: Images, shortcut and a separator

A toolbar

The ToolBar class provides a movable panel that contains a set of controls, which provide a quick access to the application actions.

#!/usr/bin/ruby

# ZetCode Ruby Qt tutorial
#
# This program creates a 
# toolbar
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: November 2012

require 'Qt'


class QtApp < Qt::MainWindow

    def initialize
        super
        
        setWindowTitle "Toolbar"
        
        init_ui
        
        resize 250, 150
        move 300, 300

        show
    end
    
    def init_ui
        newpi = Qt::Icon.new "new2.png"
        openpi = Qt::Icon.new "open2.png"
        quitpi = Qt::Icon.new "exit2.png"

        toolbar = addToolBar "main toolbar"
        toolbar.addAction newpi, "New File" 
        toolbar.addAction openpi, "Open File"
        toolbar.addSeparator
        quit = toolbar.addAction quitpi, "Quit Application"

        connect(quit, SIGNAL("triggered()"), 
            Qt::Application.instance, SLOT("quit()"))
    end
    
end

app = Qt::Application.new ARGV
QtApp.new
app.exec

We create a toolbar with three action objects and one separator.

newpi = Qt::Icon.new "new2.png"
openpi = Qt::Icon.new "open2.png"
quitpi = Qt::Icon.new "exit2.png"

Toolbar action objects will display these icons.

toolbar = addToolBar "main toolbar"

The addToolBar method of the MainWindow creates a toolbar for the application. The text string gives a toolbar a name. This name is used to reference this toolbar, because there can be multiple toolbars in one application. If we right click on the window area, we can see a checkable option, which shows or hides the toolbar.

toolbar.addSeparator

We create a vertical separator.

connect(quit, SIGNAL("triggered()"), 
    Qt::Application.instance, SLOT("quit()"))

When we click on the quit action object, the application terminates.

Toolbar
Figure: Toolbar

Undo redo

The following example demonstrates, how we can deactivate toolbar buttons on the toolbar. It is a common practice in GUI programming. For example the save button. If we save all changes of our document to the disk, the save button is deactivated in most text editors. This way the application indicates to the user that all changes are already saved.

#!/usr/bin/ruby

# ZetCode Ruby Qt tutorial
#
# This program disables/enables
#  actions on a toolbar
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: November 2012

require 'Qt'


class QtApp < Qt::MainWindow

    slots 'count()'

    def initialize
        super
        
        setWindowTitle "Toolbar"
        
        init_ui
        
        resize 250, 150
        move 300, 300

        show
    end
    
    def init_ui
        
        @count = 2
    
        undoi = Qt::Icon.new "undo.png"
        redoi = Qt::Icon.new "redo.png"
        quitpi = Qt::Icon.new "quit.png"

        toolbar = addToolBar "first toolbar"

        @und = toolbar.addAction undoi, "Undo"
        @red = toolbar.addAction redoi, "Redo"

        connect @und, SIGNAL("triggered()"), self, SLOT("count()")
        connect @red, SIGNAL("triggered()"), self, SLOT("count()")

        toolbar.addSeparator

        quit = toolbar.addAction quitpi, "Quit Application"

        connect quit, SIGNAL("triggered()"), 
            Qt::Application.instance, SLOT("quit()")
    end
    
    def count
        
        action = sender
        
        if "Undo" == action.text
            @count = @count - 1
        else 
            @count = @count + 1
        end

        if @count <= 0
            @und.setDisabled true
            @red.setDisabled false
        end

        if @count >= 5
            @und.setDisabled false
            @red.setDisabled true
        end
        
    end   
end

app = Qt::Application.new ARGV
QtApp.new
app.exec

In our example, we have three Action objects and a separator. After several clicks on the undo or redo buttons, they become deactivated. Visually, the buttons are grayed out.

@count = 2

The @count variable determines, which button is activated and deactivated.

connect @und, SIGNAL("triggered()"), self, SLOT("count()")
connect @red, SIGNAL("triggered()"), self, SLOT("count()")

Clicking on the toolbar button, the triggered signal is emitted. We connect this signal to the count method.

action = sender

Both toolbar buttons call the count method. We need to tell between them. This line determines, which action object actually emitted the signal.

if "Undo" == action.text
    @count = @count - 1
else 
    @count = @count + 1
end

The undo toolbar button subtracts 1 from the count variable. The redo adds 1. Depending on the value of the count variable, we enable or disable the toolbar buttons.

if @count <= 0
    @und.setDisabled true
    @red.setDisabled false
end

The setDisabled method activates or deactivates the toolbar buttons.

Undo redo
Figure: Undo redo

In this part of the Ruby Qt tutorial, we mentioned the menus and toolbars.