From d796c9dd933ab96ec83b9a634feedd5d32e1ba3f Mon Sep 17 00:00:00 2001 From: Timothy Pearson Date: Tue, 8 Nov 2011 12:31:36 -0600 Subject: Test conversion to TQt3 from Qt3 8c6fc1f8e35fd264dd01c582ca5e7549b32ab731 --- doc/html/tutorial1-04.html | 182 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 182 insertions(+) create mode 100644 doc/html/tutorial1-04.html (limited to 'doc/html/tutorial1-04.html') diff --git a/doc/html/tutorial1-04.html b/doc/html/tutorial1-04.html new file mode 100644 index 000000000..005aa983c --- /dev/null +++ b/doc/html/tutorial1-04.html @@ -0,0 +1,182 @@ + + + + + +TQt Tutorial - Chapter 4: Let There Be Widgets + + + + + + + +

TQt Tutorial - Chapter 4: Let There Be Widgets

+ + +

This example shows how to create your own widget, describes how to control the +minimum and maximum sizes of a widget, and introduces widget names. +

/****************************************************************
+**
+** TQt tutorial 4
+**
+****************************************************************/
+
+#include <qapplication.h>
+#include <qpushbutton.h>
+#include <qfont.h>
+
+
+class MyWidget : public TQWidget
+{
+public:
+    MyWidget( TQWidget *parent=0, const char *name=0 );
+};
+
+
+MyWidget::MyWidget( TQWidget *parent, const char *name )
+        : TQWidget( parent, name )
+{
+    setMinimumSize( 200, 120 );
+    setMaximumSize( 200, 120 );
+
+    TQPushButton *tquit = new TQPushButton( "Quit", this, "tquit" );
+    tquit->setGeometry( 62, 40, 75, 30 );
+    tquit->setFont( TQFont( "Times", 18, TQFont::Bold ) );
+
+    connect( tquit, SIGNAL(clicked()), qApp, SLOT(tquit()) );
+}
+
+
+int main( int argc, char **argv )
+{
+    TQApplication a( argc, argv );
+
+    MyWidget w;
+    w.setGeometry( 100, 100, 200, 120 );
+    a.setMainWidget( &w );
+    w.show();
+    return a.exec();
+}
+

+ + + +

Line-by-line Walkthrough +

    class MyWidget : public TQWidget
+    {
+    public:
+        MyWidget( TQWidget *parent=0, const char *name=0 );
+    };
+

Here we create a new class. Because this class inherits from TQWidget, +the new class is a widget and may be a top level window or a child +widget (like the push button in Chapter 3). +

This class has only one member, a constructor (in addition to the +members it inherits from TQWidget). The constructor is a standard TQt +widget constructor; you should always include a similar constructor +when you create widgets. +

The first argument is its parent widget. To create a top-level window +you specify a null pointer as the parent. As you can see, this widget +defaults to be a top-level window. +

The second argument is the widget's name. This is not the text +that appears in the window's title bar or in the button. It is a name +associated with a widget to make it possible to look up this widget later, and there is +also a handy debugging function that will list a complete widget hierarchy. +

    MyWidget::MyWidget( TQWidget *parent, const char *name )
+            : TQWidget( parent, name )
+

The implementation of the constructor starts here. Like most widgets, +it just passes on the parent and name to the TQWidget +constructor. +

    {
+        setMinimumSize( 200, 120 );
+        setMaximumSize( 200, 120 );
+

Because this widget doesn't know how to handle resizing, we fix its size +by setting the minimum and maximum to be equal. In the next chapter +we will show how a widget can respond to resize event from the user. +

        TQPushButton *tquit = new TQPushButton( "Quit", this, "tquit" );
+        tquit->setGeometry( 62, 40, 75, 30 );
+        tquit->setFont( TQFont( "Times", 18, TQFont::Bold ) );
+

Here we create and set up a child widget of this widget (the new widget's +parent is this) which has the widget name "tquit". The widget +name has nothing to do with the button text; it just happens to be +similar in this case. +

Note that tquit is a local variable in the constructor. MyWidget +does not keep track of it, but TQt does, and will by default delete it +when MyWidget is deleted. This is why MyWidget doesn't need a +destructor. (On the other hand, there is no harm in deleting a child +when you choose to, the child will automatically tell TQt about its +imminent death.) +

The setGeometry() call does the same as move() and resize() did in the +previous chapters. +

        connect( tquit, SIGNAL(clicked()), qApp, SLOT(tquit()) );
+    }
+

Because the MyWidget class doesn't know about the application object, it +has to connect to TQt's pointer to it, qApp. +

A widget is a software component and should know as little as possible +about its environment in order to be as general and reusable as +possible. +

Knowing the name of the application object would break this principle, +so TQt offers an alias, qApp, for the cases in which a component such as +MyWidget needs to talk to the application object. +

    int main( int argc, char **argv )
+    {
+        TQApplication a( argc, argv );
+
+        MyWidget w;
+        w.setGeometry( 100, 100, 200, 120 );
+        a.setMainWidget( &w );
+        w.show();
+        return a.exec();
+    }
+

Here we instantiate our new child, set it to be the main widget, and +execute the application. +

Behavior +

This program is very similar in behavior to the previous one. The +difference lies in the way we have implemented it. It does behave +slightly differently, however. Just try to resize it to see. +

(See Compiling for how to create a +makefile and build the application.) +

Exercises +

Try to create another MyWidget object in main(). What happens? +

Try to add more buttons or put in widgets other than TQPushButton. +

You're now ready for Chapter 5. +

[Previous tutorial] +[Next tutorial] +[Main tutorial page] +

+ +

Trademarks +

TQt 3.3.8

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