We created our sample window, and now we go on to customize it with some features fitting our needs. For each customization, we add a new function under the SampleWindow class in the previous program to define its properties, and we call this our main function to apply these properties on the sample window. In this section, we define an icon to be set on the window that we created. An icon is a small image that is created to visually emphasize the purpose of the program. It is displayed in the top-left corner of the application window. The same is also displayed in the taskbar when the application is minimized. As a prerequisite for this program, you may need an icon image with dimensions similar to the image that is used here (72 X 72). You can create your own image or download it from the book's website if you wish to use the one used in this program:

# Import required modules
import sys, time
from PySide.QtGui import QApplication, QWidget, QIcon


#...

Our next customization is to show a tooltip for the different modes of icons that are shown. Tooltip is handy when you need to display some help text or information to the users. Displaying help text for the widgets that are used in the window is an integral part for any GUI application. We use the PySide.QtGui.QToolTip class to provide tooltips (also called balloon help) for any widget. The QToolTip class defines the properties of the tooltip, such as font, color, rich text display, and so on. As an example, the font properties can be set as follows:

QToolTip.setFont(QFont("Decorative", 8, QFont.Bold))

After setting the font, we set the tooltip to the widget by calling the setToolTip() function provided by the QWidget class:

   myLabel1.setToolTip('Active Icon')

The QFont class specifies a font that has to be used to draw the text. Using the functions that are provided by this class, we can specify various attributes that we want our font to have. If the...

The next customization is to add a button to our application. The most common button that is used in any GUI is a push or command button. We push (click on) the button to command the computer to perform some action or answer a decision. Typical push buttons include: OK, Apply, Cancel, Close, Yes, No, and Help. Usually the push button is rectangular with some label on it. It can also have an optional icon associated with it. It is also possible to define a shortcut key combination to the button to which it responds on clicking the key combination.

The button emits a signal when it is activated by any external event, such as a mouse click or by pressing the spacebar, or by a keyboard shortcut. A widget may be associated with this key click event, which is executed on receiving this signal, and it is usually called a slot in Qt. We will learn more about signals and slots in the later chapters. As for now, be informed that a signal will connect to a slot on emission. There can...

The windowed applications based on type and functionality get displayed in the center for main applications, top right for notifications, and as an icon in the status bar of the screen. It is best practice for any main GUI application to display the window centered on the screen. There are two advantages of doing this. The first is to get the attention of the user, and the other is to adjust to different display formats of the various monitor screens.

There is no straightforward method to center the window by calling a predefined function of some class. Therefore, we write our own method, called center, to position the window central to any screen. This method takes the object that it is calling and centers it with respect to the screen that it is displayed on:

    def center(self):
        """ Function to center the application
        """
        qRect = self.frameGeometry()
        centerPoint = QDesktopWidget().availableGeometry...