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< td align = "right" valign = "center" > < img src = "logo32.png" align = "right" width = "64" height = "32" border = "0" > < / td > < / tr > < / table > < h1 align = center > TQt Tutorial - Chapter 3: Family Values< / h1 >
< p > < center > < img src = "t3.png" alt = "Screenshot of tutorial three" > < / center >
< p > This example shows how to create parent and child widgets.
< p > We'll keep it simple and use just a single parent and a lone child.
< p > < pre > /****************************************************************
**
** TQt tutorial 3
**
****************************************************************/
#include < < a href = "qapplication-h.html" > ntqapplication.h< / a > >
#include < < a href = "tqpushbutton-h.html" > tqpushbutton.h< / a > >
#include < < a href = "tqfont-h.html" > tqfont.h< / a > >
#include < < a href = "tqvbox-h.html" > tqvbox.h< / a > >
int main( int argc, char **argv )
{
< a href = "ntqapplication.html" > TQApplication< / a > a( argc, argv );
< a href = "tqvbox.html" > TQVBox< / a > box;
box.< a href = "tqwidget.html#resize" > resize< / a > ( 200, 120 );
< a href = "tqpushbutton.html" > TQPushButton< / a > quit( "Quit", & box );
quit.< a href = "tqwidget.html#setFont" > setFont< / a > ( TQFont( "Times", 18, TQFont::Bold ) );
TQObject::< a href = "tqobject.html#connect" > connect< / a > ( & quit, TQ_SIGNAL(< a href = "tqbutton.html#clicked" > clicked< / a > ()), & a, TQ_SLOT(< a href = "ntqapplication.html#quit" > quit< / a > ()) );
a.< a href = "ntqapplication.html#setMainWidget" > setMainWidget< / a > ( & box );
box.< a href = "tqwidget.html#show" > show< / a > ();
return a.< a href = "ntqapplication.html#exec" > exec< / a > ();
}
< / pre >
< p > < h2 > Line-by-line Walkthrough
< / h2 >
< a name = "1" > < / a > < p > < pre > #include < < a href = "tqvbox-h.html" > tqvbox.h< / a > >
< / pre >
< p > We add an include of tqvbox.h to get the layout class we'll use.
< p > < pre > < a href = "tqvbox.html" > TQVBox< / a > box;
< / pre >
< p > Here we simply create a vertical box container. The < a href = "tqvbox.html" > TQVBox< / a > arranges
its child widgets in a vertical row, one above the other, handing out
space according to each child's < a href = "tqwidget.html#sizePolicy" > TQWidget::sizePolicy< / a > ().
< p > < pre > < a name = "x2300" > < / a > box.< a href = "tqwidget.html#resize" > resize< / a > ( 200, 120 );
< / pre >
< p > We set its width to 200 pixels and the height to 120 pixels.
< p > < pre > < a href = "tqpushbutton.html" > TQPushButton< / a > quit( "Quit", & box );
< / pre >
< p > A child is born.
< p > This < a href = "tqpushbutton.html" > TQPushButton< / a > is created with both a text ("Quit") and a parent
(box). A child widget is always on top of its parent. When
displayed, it is clipped by its parent's bounds.
< p > The parent widget, the TQVBox, automatically adds the child centered in
its box. Because nothing else is added, the button gets all the space
the parent has.
< p > < pre > < a name = "x2302" > < / a > box.< a href = "tqwidget.html#show" > show< / a > ();
< / pre >
< p > When a parent widget is shown, it will call show for all its children
(except those on which you have done an explicit < a href = "tqwidget.html#hide" > TQWidget::hide< / a > ()).
< p > < h2 > Behavior
< / h2 >
< a name = "2" > < / a > < p > The button no longer fills the entire widget. Instead, it gets a
"natural" size. This is because there is now a new top-level widget,
which uses the button's size hint and size change policy to set the
button's size and position. (See < a href = "tqwidget.html#sizeHint" > TQWidget::sizeHint< / a > () and < a href = "tqwidget.html#setSizePolicy" > TQWidget::setSizePolicy< / a > () for more information about these functions.)
< p > (See < a href = "tutorial1-01.html#compiling" > Compiling< / a > for how to create a
makefile and build the application.)
< p > < h2 > Exercises
< / h2 >
< a name = "3" > < / a > < p > Try resizing the window. How does the button change? What is the
button's size-change policy? What happens to the button's height if
you run the program with a bigger font? What happens if you try to
make the window < em > really< / em > small?
< p > You're now ready for < a href = "tutorial1-04.html" > Chapter 4.< / a >
< p > [< a href = "tutorial1-02.html" > Previous tutorial< / a > ]
[< a href = "tutorial1-04.html" > Next tutorial< / a > ]
[< a href = "tutorial.html" > Main tutorial page< / a > ]
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