Dialogs
In this part of the Ruby Qt programming tutorial, we will work with dialogs.
Dialog windows or dialogs are an indispensable part of most modern GUI applications. A dialog is defined as a conversation between two or more persons. In a computer application a dialog is a window which is used to "talk" to the application. A dialog is used to input data, modify data, change the application settings etc. Dialogs are important means of communication between a user and a computer program.
Message boxes
Message boxes are convenient dialogs that provide messages to the user of the application. The message consists of text and image data.
#!/usr/bin/ruby
# ZetCode Ruby Qt tutorial
#
# This program demonstrates
# MessageBox dialogs
#
# author: jan bodnar
# website: www.zetcode.com
# last modified: July 2009
require 'Qt'
class QtApp < Qt::Widget
slots 'showDialog()'
def initialize
super
setWindowTitle "Message dialogs"
init_ui
resize 250, 150
move 300, 300
show
end
def init_ui
grid = Qt::GridLayout.new self
grid.setSpacing 2
error = Qt::PushButton.new "Error", self
warning = Qt::PushButton.new "Warning", self
question = Qt::PushButton.new "Question", self
information = Qt::PushButton.new "Information", self
about = Qt::PushButton.new "About", self
grid.addWidget error, 0, 0
grid.addWidget warning, 0, 1
grid.addWidget question, 1, 0
grid.addWidget information, 1, 1
grid.addWidget about, 2, 0
connect(error, SIGNAL("clicked()"),
self, SLOT("showDialog()"))
connect(warning, SIGNAL("clicked()"),
self, SLOT("showDialog()"))
connect(question, SIGNAL("clicked()"),
self, SLOT("showDialog()"))
connect(information, SIGNAL("clicked()"),
self, SLOT("showDialog()"))
connect(about, SIGNAL("clicked()"),
self, SLOT("showDialog()"))
end
def showDialog
button = sender
if "Error" == button.text
Qt::MessageBox.critical self, "Error", "Error loading file!"
elsif "Warning" == button.text
Qt::MessageBox.warning self, "Warning", "Operation not permitted!"
elsif "Question" == button.text
Qt::MessageBox.question self, "Question", "Are you sure to quit?"
elsif "Information" == button.text
Qt::MessageBox.information self, "Information", "Download completed."
elsif "About" == button.text
Qt::MessageBox.about self, "About", "ZetCode Ruby Qt tutorial."
end
end
end
app = Qt::Application.new ARGV
QtApp.new
app.exec
We use the GridLayout manager to set up a grid of five buttons. Each of the buttons shows a different message box.
if "Error" == button.text
Qt::MessageBox.critical self, "Error", "Error loading file!"
In case we pressed the error button, we show the error dialog. We use static methods of the MessageBox class to show the message boxes.
InputDialog
The InputDialog class provides a simple convenience dialog to get a single value from the user. The input value can be a string, a number or an item from a list. A label must be set to tell the user what they should enter.
#!/usr/bin/ruby
# ZetCode Ruby Qt tutorial
#
# This program shows an input
# dialog
#
# author: jan bodnar
# website: www.zetcode.com
# last modified: July 2009
require 'Qt'
class QtApp < Qt::Widget
slots 'showDialog()'
def initialize
super
setWindowTitle "Input dialog"
init_ui
resize 400, 80
move 300, 300
show
end
def init_ui
show = Qt::PushButton.new "Dialog", self
connect(show, SIGNAL("clicked()"),
self, SLOT("showDialog()"))
show.move 20, 20
@edit = Qt::LineEdit.new self
@edit.move 130, 22
end
def showDialog
text = Qt::InputDialog.getText self, "Input Dialog",
"Enter your name"
if text != nil
name = text.strip
if not name.empty?
@edit.setText name
end
end
end
end
app = Qt::Application.new ARGV
QtApp.new
app.exec
In the code example, we have a button and a line edit. The button shows an input dialog. We get some text and the text is shown in the line edit widget.
text = Qt::InputDialog.getText self, "Input Dialog",
"Enter your name"
The getText static method creates the input dialog. The text from the dialog is stored in the text variable.
if text != nil
name = text.strip
if not name.empty?
@edit.setText name
end
end
Before we update the line edit, we ensure, that the text variable is not null and that it is not empty and does not consists only from spaces.
ColorDialog
The ColorDialog class provides a dialog widget for specifying colors. The color dialog's function is to allow users to choose colors.
#!/usr/bin/ruby
# ZetCode Ruby Qt tutorial
#
# In this program, we use the
# ColorDialog to change the color
# of a label text
#
# author: jan bodnar
# website: www.zetcode.com
# last modified: July 2009
require 'Qt'
class QtApp < Qt::Widget
slots 'showDialog()'
def initialize
super
setWindowTitle "Color dialog"
init_ui
resize 400, 300
move 300, 300
show
end
def init_ui
@label = Qt::Label.new "ZetCode Ruby Qt tutorial", self
vbox = Qt::VBoxLayout.new self
@label.setAlignment Qt::AlignCenter
vbox.addWidget @label
end
def mousePressEvent event
color = Qt::ColorDialog.getColor
if not color.isValid
return
end
@label.setStyleSheet "QWidget { color: %s }" % color.name
end
end
app = Qt::Application.new ARGV
QtApp.new
app.exec
We show a some text in the center of the window. By clicking on the area of the window, we show a color dialog. We change the text foreground color to the selected color from the dialog.
def mousePressEvent event ... end
In order to receive mouse press events for our window, we must reimplement the mousePressEvent method.
color = Qt::ColorDialog.getColor
The ColorDialog is being created. The selected color is stored in the color variable.
@label.setStyleSheet "QWidget { color: %s }" % color.name
Here we update the foreground color of the label's text.
FontDialog
The FontDialog class provides a dialog widget for selecting a font.
#!/usr/bin/ruby
# ZetCode Ruby Qt tutorial
#
# In this program, we use the
# FontDialog to change the font
# of a label text
#
# author: jan bodnar
# website: www.zetcode.com
# last modified: July 2009
require 'Qt'
class QtApp < Qt::Widget
slots 'showDialog()'
def initialize
super
setWindowTitle "Font dialog"
init_ui
resize 400, 300
move 300, 300
show
end
def init_ui
@label = Qt::Label.new "ZetCode Ruby Qt tutorial", self
vbox = Qt::VBoxLayout.new self
@label.setAlignment Qt::AlignCenter
vbox.addWidget @label
end
def mousePressEvent event
ok = Qt::Boolean.new
font = Qt::FontDialog.getFont ok
if not ok
return
end
@label.setFont font
end
end
app = Qt::Application.new ARGV
QtApp.new
app.exec
This example is similar to the previous one. This time, we change the font of the text.
font = Qt::FontDialog.getFont ok
The FontDialog is being created.
if not ok
return
end
The boolean ok variable is true, if we clicked on the OK button of the dialog. We return from the method, if the cancel button was pressed.
@label.setFont font
We update the label to the newly selected font.
In this part of the Ruby Qt tutorial, we worked with dialog windows.