Qt Widgets

Qt Widgets is an interesting module that supports quite a lot of widgets, such as buttons, labels, edit, combo, list, dialog, and so on. QWidget is the base class of all of the widgets, while QObject is the base class of pretty much every Qt class. While many programming languages refer to as UI controls, Qt refers to them as widgets. Though Qt works on many platforms, its home remains Linux; widgets are common in the Linux world. 

Writing our first Qt GUI application

Our first console application is really cool, isn't it? Let's continue exploring further. This time, let's write a simple GUI-based Hello World program. The procedure will remain almost the same, except for some minor changes in main.cpp. Refer to the following for the complete code:

Figure 5.7

Wait a minute. Let me explain the need for QApplication in line number 23 and line number 29. Every Qt GUI application must have exactly one instance of the QApplication instance. QApplication provides support for command-line...