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6<title>Walkthrough: A Simple Application</title>
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30<font color="#004faf">Functions</font></a>
31</td>
32<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Walkthrough: A Simple Application</h1>
33
34
35
36<p>
37<p> This walkthrough shows simple use of <a href="qmainwindow.html">QMainWindow</a>, <a href="qmenubar.html">QMenuBar</a>, <a href="qpopupmenu.html">QPopupMenu</a>, <a href="qtoolbar.html">QToolBar</a> and <a href="qstatusbar.html">QStatusBar</a> - classes that every
38modern application window tends to use. (See also <a href="tutorial2.html">Tutorial #2</a>.)
39<p> It also illustrates some aspects of <a href="qwhatsthis.html">QWhatsThis</a> (for simple help) and a
40typical <tt>main()</tt> using <a href="qapplication.html">QApplication</a>.
41<p> Finally, it shows a typical print function based on <a href="qprinter.html">QPrinter</a>.
42<p> <h2> The declaration of ApplicationWindow
43</h2>
44<a name="1"></a><p> Here's the header file in full:
45<p> <pre>/****************************************************************************
46** $Id: simple-application.html 2051 2007-02-21 10:04:20Z chehrlic $
47**
48** Copyright (C) 1992-2007 Trolltech ASA. All rights reserved.
49**
50** This file is part of an example program for Qt. This example
51** program may be used, distributed and modified without limitation.
52**
53*****************************************************************************/
54
55#ifndef APPLICATION_H
56#define APPLICATION_H
57
58#include &lt;<a href="qmainwindow-h.html">qmainwindow.h</a>&gt;
59
60class QTextEdit;
61
62class ApplicationWindow: public <a href="qmainwindow.html">QMainWindow</a>
63{
64 <a href="metaobjects.html#Q_OBJECT">Q_OBJECT</a>
65
66public:
67 ApplicationWindow();
68 ~ApplicationWindow();
69
70protected:
71 void closeEvent( <a href="qcloseevent.html">QCloseEvent</a>* );
72
73private slots:
74 void newDoc();
75 void choose();
76 void load( const <a href="qstring.html">QString</a> &amp;fileName );
77 void save();
78 void saveAs();
79 void print();
80
81 void about();
82 void aboutQt();
83
84private:
85 <a href="qprinter.html">QPrinter</a> *printer;
86 <a href="qtextedit.html">QTextEdit</a> *e;
87 <a href="qstring.html">QString</a> filename;
88};
89
90
91#endif
92</pre>
93
94<p> It declares a class that inherits <a href="qmainwindow.html">QMainWindow</a>, with slots and private
95variables. The class pre-declaration of <a href="qtextedit.html">QTextEdit</a> at the beginning
96(instead of an include) helps to speed up compilation. With this
97trick, <tt>make depend</tt> won't insist on recompiling every <tt>.cpp</tt> file that
98includes <tt>application.h</tt> when <a href="qtextedit-h.html">qtextedit.h</a> changes.
99<p> <a name="simplemain"></a>
100<h2> A simple main()
101</h2>
102<a name="2"></a><p> Here is <tt>main.cpp</tt> in full:
103<p> <pre>/****************************************************************************
104** $Id: simple-application.html 2051 2007-02-21 10:04:20Z chehrlic $
105**
106** Copyright (C) 1992-2007 Trolltech ASA. All rights reserved.
107**
108** This file is part of an example program for Qt. This example
109** program may be used, distributed and modified without limitation.
110**
111*****************************************************************************/
112
113#include &lt;<a href="qapplication-h.html">qapplication.h</a>&gt;
114#include "application.h"
115
116int main( int argc, char ** argv ) {
117 <a href="qapplication.html">QApplication</a> a( argc, argv );
118 ApplicationWindow *mw = new ApplicationWindow();
119 mw-&gt;<a href="qwidget.html#setCaption">setCaption</a>( "Qt Example - Application" );
120<a name="x1598"></a> mw-&gt;<a href="qwidget.html#show">show</a>();
121<a name="x1599"></a> a.<a href="qobject.html#connect">connect</a>( &amp;a, SIGNAL(<a href="qapplication.html#lastWindowClosed">lastWindowClosed</a>()), &amp;a, SLOT(<a href="qapplication.html#quit">quit</a>()) );
122 return a.<a href="qapplication.html#exec">exec</a>();
123}
124</pre>
125
126<p> Now we'll look at <tt>main.cpp</tt> in detail.
127<p>
128
129<pre> int main( int argc, char ** argv ) {
130 <a href="qapplication.html">QApplication</a> a( argc, argv );
131</pre>
132<p> With the above line, we create a <a href="qapplication.html">QApplication</a> object with the usual
133constructor and let it
134parse <em>argc</em> and <em>argv</em>. QApplication itself takes care of X11-specific
135command-line options like <em>-geometry</em>, so the program will automatically
136behave the way X clients are expected to.
137<p> <pre> ApplicationWindow *mw = new ApplicationWindow();
138 mw-&gt;<a href="qwidget.html#setCaption">setCaption</a>( "Qt Example - Application" );
139 <a name="x2115"></a> mw-&gt;<a href="qwidget.html#show">show</a>();
140</pre>
141<p> We create an <em>ApplicationWindow</em> as a top-level widget, set its window
142system caption to "Document 1", and <em>show()</em> it.
143<p> <a name="close"></a>
144<pre> a.<a href="qobject.html#connect">connect</a>( &amp;a, SIGNAL(<a href="qapplication.html#lastWindowClosed">lastWindowClosed</a>()), &amp;a, SLOT(<a href="qapplication.html#quit">quit</a>()) );
145</pre>
146<p> When the application's last window is closed, it should quit. Both
147the signal and the slot are predefined members of <a href="qapplication.html">QApplication</a>.
148<p> <pre> return a.<a href="qapplication.html#exec">exec</a>();
149</pre>
150<p> Having completed the application's initialization, we start the main
151event loop (the GUI), and eventually return the error code
152that QApplication returns when it leaves the event loop.
153<p> <pre> }
154</pre>
155<p> <a name="ApplicationWindow"></a>
156<h2> The Implementation of ApplicationWindow
157</h2>
158<a name="3"></a><p>
159
160<p> Since the implementation is quite large (almost 300 lines) we
161won't list the whole thing. (The source code is included in the
162examples/application directory.) Before we start with the constructor
163there are three <tt>#include</tt>s worth mentioning:
164<p> <pre> #include "filesave.xpm"
165 #include "fileopen.xpm"
166 #include "fileprint.xpm"
167</pre>
168<p> The tool buttons in our application wouldn't look good without icons!
169These icons can be found in the XPM files included above. If you ever
170moved a program to a different location and wondered why icons were
171missing afterwards you will probably agree that it is a good idea to
172compile them into the binary. This is what we are doing here.
173<p> <pre> ApplicationWindow::ApplicationWindow()
174 : <a href="qmainwindow.html">QMainWindow</a>( 0, "example application main window", WDestructiveClose | WGroupLeader )
175 {
176</pre>
177<p> <em>ApplicationWindow</em> inherits <a href="qmainwindow.html">QMainWindow</a>, the Qt class that provides
178typical application main windows, with menu bars, toolbars, etc.
179<p> <pre> printer = new <a href="qprinter.html">QPrinter</a>( QPrinter::HighResolution );
180</pre>
181<p> The application example can print things, and we chose to have a
182<a href="qprinter.html">QPrinter</a> object lying around so that when the user changes a setting
183during one printing, the new setting will be the default next time.
184<p> <pre> <a href="qpixmap.html">QPixmap</a> openIcon, saveIcon, printIcon;
185</pre>
186<p> For the sake of simplicity, our example only has a few commands in the
187toolbar. The above variables are used to hold an icon for each of
188them.
189<p> <pre> <a href="qtoolbar.html">QToolBar</a> * fileTools = new <a href="qtoolbar.html">QToolBar</a>( this, "file operations" );
190</pre>
191<p> We create a toolbar in <em>this</em> window ...
192<p> <pre> fileTools-&gt;<a href="qtoolbar.html#setLabel">setLabel</a>( "File Operations" );
193</pre>
194<p> ... and define a title for it. When a user drags the toolbar out of
195its location and floats it over the desktop, the toolbar-window will
196show "File Operations" as caption.
197<p> <pre> openIcon = QPixmap( fileopen );
198 QToolButton * fileOpen
199 = new <a href="qtoolbutton.html">QToolButton</a>( openIcon, "Open File", <a href="qstring.html#QString-null">QString::null</a>,
200 this, SLOT(choose()), fileTools, "open file" );
201</pre>
202<p> Now we create the first tool button for the <em>fileTools</em> toolbar
203with the appropriate icon and the tool-tip text "Open File".
204The <tt>fileopen.xpm</tt> we included at the beginning
205contains the definition of a pixmap called <em>fileopen</em>.
206We use this icon to illustrate our first tool button.
207<p> <pre> saveIcon = QPixmap( filesave );
208 QToolButton * fileSave
209 = new <a href="qtoolbutton.html">QToolButton</a>( saveIcon, "Save File", QString::null,
210 this, SLOT(save()), fileTools, "save file" );
211
212 printIcon = QPixmap( fileprint );
213 QToolButton * filePrint
214 = new <a href="qtoolbutton.html">QToolButton</a>( printIcon, "Print File", QString::null,
215 this, SLOT(print()), fileTools, "print file" );
216</pre>
217<p> In a similar way we create two more tool buttons in this toolbar, each with
218appropriate icons and tool-tip text. All three buttons are connected
219to appropriate slots in this object; for example, the "Print File" button
220to <a href="#printer">ApplicationWindow::print()</a>.
221<p> <pre> (void)QWhatsThis::whatsThisButton( fileTools );
222</pre>
223<p> The fourth button in the toolbar is somewhat peculiar: it's the one that
224provides "What's This?" help. This must be set up using a special
225function, as its mouse interface is unusual.
226<p> <pre> const char * fileOpenText = "&lt;p&gt;&lt;img source=\"fileopen\"&gt; "
227 "Click this button to open a &lt;em&gt;new file&lt;/em&gt;.&lt;br&gt;"
228 "You can also select the &lt;b&gt;Open&lt;/b&gt; command "
229 "from the &lt;b&gt;File&lt;/b&gt; menu.&lt;/p&gt;";
230
231 QWhatsThis::<a href="qwhatsthis.html#add">add</a>( fileOpen, fileOpenText );
232</pre>
233<p> With the above line we add the "What's This?" help-text to the
234<em>fileOpen</em> button...
235<p> <pre> QMimeSourceFactory::<a href="qmimesourcefactory.html#defaultFactory">defaultFactory</a>()-&gt;setPixmap( "fileopen", openIcon );
236</pre>
237<p> ... and tell the rich-text engine that when a help-text (like the one
238saved in <em>fileOpenText</em>) requests an image named "fileopen", the <em>openIcon</em> pixmap is used.
239<p> <pre> const char * fileSaveText = "&lt;p&gt;Click this button to save the file you "
240 "are editing. You will be prompted for a file name.\n"
241 "You can also select the &lt;b&gt;Save&lt;/b&gt; command "
242 "from the &lt;b&gt;File&lt;/b&gt; menu.&lt;/p&gt;";
243
244 QWhatsThis::<a href="qwhatsthis.html#add">add</a>( fileSave, fileSaveText );
245 const char * filePrintText = "Click this button to print the file you "
246 "are editing.\n"
247 "You can also select the Print command "
248 "from the File menu.";
249
250 QWhatsThis::<a href="qwhatsthis.html#add">add</a>( filePrint, filePrintText );
251</pre>
252<p> The "What's This?" help of the remaining two buttons doesn't make use
253of pixmaps, therefore all we need to do is to add the help-text to the
254button. Be careful though: To invoke the rich-text elements in <tt>fileSaveText()</tt>, the entire string must be surrounded by &lt;p&gt; and
255&lt;/p&gt;. In <tt>filePrintText()</tt>, we don't have rich-text elements, so
256this is not necessary.
257<p> <pre> <a href="qpopupmenu.html">QPopupMenu</a> * file = new <a href="qpopupmenu.html">QPopupMenu</a>( this );
258 <a href="qmainwindow.html#menuBar">menuBar</a>()-&gt;insertItem( "&amp;File", file );
259</pre>
260<p> Next we create a <a href="qpopupmenu.html">QPopupMenu</a> for the <em>File</em> menu and
261add it to the menu bar. With the ampersand in front of the letter F,
262we allow the user to use the shortcut <em>Alt+F</em> to pop up this menu.
263<p> <pre> file-&gt;<a href="qmenudata.html#insertItem">insertItem</a>( "&amp;New", this, SLOT(newDoc()), CTRL+Key_N );
264</pre>
265<p> Its first entry is connected to the (yet to be implemented) slot <tt>newDoc()</tt>. When the user chooses this <em>New</em> entry (e.g. by typing the
266letter N as marked by the ampersand) or uses the
267<em>Ctrl+N</em> accelerator, a new editor-window will pop up.
268<p> <pre> int id;
269 id = file-&gt;<a href="qmenudata.html#insertItem">insertItem</a>( openIcon, "&amp;Open...",
270 this, SLOT(choose()), CTRL+Key_O );
271 file-&gt;<a href="qmenudata.html#setWhatsThis">setWhatsThis</a>( id, fileOpenText );
272
273 id = file-&gt;<a href="qmenudata.html#insertItem">insertItem</a>( saveIcon, "&amp;Save",
274 this, SLOT(save()), CTRL+Key_S );
275 file-&gt;<a href="qmenudata.html#setWhatsThis">setWhatsThis</a>( id, fileSaveText );
276
277 id = file-&gt;<a href="qmenudata.html#insertItem">insertItem</a>( "Save &amp;As...", this, SLOT(saveAs()) );
278 file-&gt;<a href="qmenudata.html#setWhatsThis">setWhatsThis</a>( id, fileSaveText );
279</pre>
280<p> We populate the <em>File</em> menu with three more commands (<em>Open</em>, <em>Save</em> and
281<em>Save As</em>), and set "What's This?" help for them. Note in particular
282that "What's This?" help and pixmaps are used in both the toolbar (above)
283and the menu bar (here). (See <a href="qaction.html">QAction</a> and the <tt>examples/action</tt>
284example for a shorter and easier approach.)
285<p> <pre> file-&gt;<a href="qmenudata.html#insertSeparator">insertSeparator</a>();
286</pre>
287<p> Then we insert a separator, ...
288<p> <pre> id = file-&gt;<a href="qmenudata.html#insertItem">insertItem</a>( printIcon, "&amp;Print...",
289 this, SLOT(print()), CTRL+Key_P );
290 file-&gt;<a href="qmenudata.html#setWhatsThis">setWhatsThis</a>( id, filePrintText );
291
292 file-&gt;<a href="qmenudata.html#insertSeparator">insertSeparator</a>();
293
294 file-&gt;<a href="qmenudata.html#insertItem">insertItem</a>( "&amp;Close", this, SLOT(<a href="qwidget.html#close">close</a>()), CTRL+Key_W );
295 file-&gt;<a href="qmenudata.html#insertItem">insertItem</a>( "&amp;Quit", qApp, SLOT( <a href="qapplication.html#closeAllWindows">closeAllWindows</a>() ), CTRL+Key_Q );
296</pre>
297<p> ... the <em>Print</em> command with "What's This?" help, another separator and
298two more commands (<em>Close</em> and <em>Quit</em>) without "What's This?" and pixmaps.
299In case of the <em>Close</em> command, the signal is connected
300to the <em>close()</em> slot of the respective <em>ApplicationWindow</em> object whilst
301the <em>Quit</em> command affects the entire application.
302<p> Because <em>ApplicationWindow</em> is a <a href="qwidget.html">QWidget</a>, the <em>close()</em> function
303triggers a call to <a href="#closeEvent">closeEvent()</a> which we
304will implement later.
305<p> <a name="common_constructor"></a>
306<pre> <a href="qmainwindow.html#menuBar">menuBar</a>()-&gt;insertSeparator();
307</pre>
308<p> Now that we have done the File menu we shift our focus back to the
309menu bar and insert a separator. From now on further menu bar entries
310will be aligned to the right if the windows system style requires it.
311<p> <pre> <a href="qpopupmenu.html">QPopupMenu</a> * help = new <a href="qpopupmenu.html">QPopupMenu</a>( this );
312 <a href="qmainwindow.html#menuBar">menuBar</a>()-&gt;insertItem( "&amp;Help", help );
313
314 help-&gt;<a href="qmenudata.html#insertItem">insertItem</a>( "&amp;About", this, SLOT(about()), Key_F1 );
315 help-&gt;<a href="qmenudata.html#insertItem">insertItem</a>( "About &amp;Qt", this, SLOT(aboutQt()) );
316 help-&gt;<a href="qmenudata.html#insertSeparator">insertSeparator</a>();
317 help-&gt;<a href="qmenudata.html#insertItem">insertItem</a>( "What's &amp;This", this, SLOT(<a href="qmainwindow.html#whatsThis">whatsThis</a>()), SHIFT+Key_F1 );
318</pre>
319<p> We create a <em>Help</em> menu, add it to the menu bar, and insert a few
320commands. Depending on the style it will appear on the right hand
321side of the menu bar or not.
322<p> <pre> e = new <a href="qtextedit.html">QTextEdit</a>( this, "editor" );
323 e-&gt;<a href="qwidget.html#setFocus">setFocus</a>();
324 <a href="qmainwindow.html#setCentralWidget">setCentralWidget</a>( e );
325</pre>
326<p> Now we create a simple text-editor, set the initial focus to it,
327and make it the window's central widget.
328<p> <a href="qmainwindow.html#centralWidget">QMainWindow::centralWidget</a>() is the heart of the entire application:
329It's what menu bar, statusbar and toolbars are all arranged around. Since
330the central widget is a text editing widget, we can now reveal that
331our simple application is a text editor. :)
332<p> <pre> <a href="qmainwindow.html#statusBar">statusBar</a>()-&gt;message( "Ready", 2000 );
333</pre>
334<p> We make the statusbar say "Ready" for two seconds at startup, just to
335tell the user that the window has finished initialization and can be
336used.
337<p> <pre> <a href="qwidget.html#resize">resize</a>( 450, 600 );
338</pre>
339<p> Finally it's time to resize the new window to a a nice default size.
340<p> <pre> }
341</pre>
342<p> We have now finished with the constructor. Now we'll deal with the
343destructor.
344<p> <pre> ApplicationWindow::~ApplicationWindow()
345 {
346 delete printer;
347 }
348</pre>
349<p> The only thing an <em>ApplicationWindow</em> widget needs to do in its
350destructor is to delete the printer it created. All other objects are
351child widgets, which Qt will delete when appropriate.
352<p> Now our task is to implement all the slots mentioned in the header file
353and used in the constructor.
354<p> <a name="newDoc()"></a>
355<pre> void ApplicationWindow::newDoc()
356 {
357 ApplicationWindow *ed = new ApplicationWindow;
358 ed-&gt;<a href="qwidget.html#setCaption">setCaption</a>("Qt Example - Application");
359 ed-&gt;<a href="qwidget.html#show">show</a>();
360 }
361</pre>
362<p> This slot, connected to the <em>File|New</em> menu item, simply creates a
363new <em>ApplicationWindow</em> and shows it.
364<p> <a name="choose()"></a>
365<pre> void ApplicationWindow::choose()
366 {
367 <a href="qstring.html">QString</a> fn = QFileDialog::<a href="qfiledialog.html#getOpenFileName">getOpenFileName</a>( QString::null, QString::null,
368 this);
369 if ( !fn.<a href="qstring.html#isEmpty">isEmpty</a>() )
370 load( fn );
371 else
372 <a href="qmainwindow.html#statusBar">statusBar</a>()-&gt;message( "Loading aborted", 2000 );
373 }
374</pre>
375<p> The <em>choose()</em> slot is connected to the <em>Open</em> menu item and
376tool button. With a little help from <a href="qfiledialog.html#getOpenFileName">QFileDialog::getOpenFileName</a>(), it
377asks the user for a file name and then either loads that file or gives an
378error message in the statusbar.
379<p> <pre> void ApplicationWindow::load( const <a href="qstring.html">QString</a> &amp;fileName )
380 {
381 <a href="qfile.html">QFile</a> f( fileName );
382 if ( !f.<a href="qfile.html#open">open</a>( <a href="qfile.html#open">IO_ReadOnly</a> ) )
383 return;
384
385 <a href="qtextstream.html">QTextStream</a> ts( &amp;f );
386 e-&gt;<a href="qtextedit.html#setText">setText</a>( ts.<a href="qtextstream.html#read">read</a>() );
387 e-&gt;<a href="qtextedit.html#setModified">setModified</a>( FALSE );
388 <a href="qwidget.html#setCaption">setCaption</a>( fileName );
389 <a href="qmainwindow.html#statusBar">statusBar</a>()-&gt;message( "Loaded document " + fileName, 2000 );
390 }
391</pre>
392<p> This function loads a file into the editor. When it's done, it sets the
393window system caption to the file name and displays a success message in
394the statusbar for two seconds. With files that exist but are not
395readable, nothing happens.
396<p> <a name="save()"></a>
397<pre> void ApplicationWindow::save()
398 {
399 if ( filename.isEmpty() ) {
400 saveAs();
401 return;
402 }
403
404 <a href="qstring.html">QString</a> text = e-&gt;<a href="qtextedit.html#text">text</a>();
405 <a href="qfile.html">QFile</a> f( filename );
406 if ( !f.<a href="qfile.html#open">open</a>( <a href="qfile.html#open">IO_WriteOnly</a> ) ) {
407 <a href="qmainwindow.html#statusBar">statusBar</a>()-&gt;message( QString("Could not write to %1").arg(filename),
408 2000 );
409 return;
410 }
411
412 <a href="qtextstream.html">QTextStream</a> t( &amp;f );
413 t &lt;&lt; text;
414 f.<a href="qfile.html#close">close</a>();
415</pre>
416<p> As its name suggests, this function saves the current file. If no
417filename has been specified so far, the <a href="#saveAs()">saveAs()</a> function is called. Unwritable files cause the <em>ApplicationWindow</em> object to provide an error-message in the statusbar.
418Note that there is more than one way to do this:
419compare the above <tt>statusBar()-&gt;message()</tt> line with the equivalent
420code in the <tt>load()</tt> function.
421<p> <pre> e-&gt;<a href="qtextedit.html#setModified">setModified</a>( FALSE );
422</pre>
423<p> Tell the editor that the contents haven't been edited since the last
424save. When the user does some further editing and wishes to close the
425window without explicit saving, <a href="#closeEvent">ApplicationWindow::closeEvent()</a> will ask about it.
426<p> <pre> <a href="qwidget.html#setCaption">setCaption</a>( filename );
427</pre>
428<p> It may be that the document was saved under a different name than the
429old caption suggests, so we set the window caption just to be sure.
430<p> <pre> <a href="qmainwindow.html#statusBar">statusBar</a>()-&gt;message( QString( "File %1 saved" ).arg( filename ), 2000 );
431 }
432</pre>
433<p> With a message in the statusbar, we inform the user that the file
434was saved successfully.
435<p> <a name="saveAs()"></a>
436<pre> void ApplicationWindow::saveAs()
437 {
438 <a href="qstring.html">QString</a> fn = QFileDialog::<a href="qfiledialog.html#getSaveFileName">getSaveFileName</a>( QString::null, QString::null,
439 this );
440 if ( !fn.<a href="qstring.html#isEmpty">isEmpty</a>() ) {
441 filename = fn;
442 save();
443 } else {
444 <a href="qmainwindow.html#statusBar">statusBar</a>()-&gt;message( "Saving aborted", 2000 );
445 }
446 }
447</pre>
448<p> This function asks for a new name, saves the document under that name,
449and implicitly changes the window system caption to the new name.
450<p> <a name="printer"></a>
451<p> <pre> void ApplicationWindow::print()
452 {
453 printer-&gt;<a href="qprinter.html#setFullPage">setFullPage</a>( TRUE );
454 if ( printer-&gt;<a href="qprinter.html#setup">setup</a>(this) ) { // printer dialog
455 <a href="qmainwindow.html#statusBar">statusBar</a>()-&gt;message( "Printing..." );
456 <a href="qpainter.html">QPainter</a> p;
457 if( !p.<a href="qpainter.html#begin">begin</a>( printer ) ) { // paint on printer
458 <a href="qmainwindow.html#statusBar">statusBar</a>()-&gt;message( "Printing aborted", 2000 );
459 return;
460 }
461
462 <a href="qpaintdevicemetrics.html">QPaintDeviceMetrics</a> metrics( p.<a href="qpainter.html#device">device</a>() );
463 int dpiy = metrics.<a href="qpaintdevicemetrics.html#logicalDpiY">logicalDpiY</a>();
464 int margin = (int) ( (2/2.54)*dpiy ); // 2 cm margins
465 <a href="qrect.html">QRect</a> view( margin, margin, metrics.<a href="qpaintdevicemetrics.html#width">width</a>() - 2*margin, metrics.<a href="qpaintdevicemetrics.html#height">height</a>() - 2*margin );
466 <a href="qsimplerichtext.html">QSimpleRichText</a> richText( QStyleSheet::<a href="qstylesheet.html#convertFromPlainText">convertFromPlainText</a>(e-&gt;<a href="qtextedit.html#text">text</a>()),
467 QFont(),
468 e-&gt;<a href="qtextedit.html#context">context</a>(),
469 e-&gt;<a href="qtextedit.html#styleSheet">styleSheet</a>(),
470 e-&gt;<a href="qtextedit.html#mimeSourceFactory">mimeSourceFactory</a>(),
471 view.<a href="qrect.html#height">height</a>() );
472 richText.<a href="qsimplerichtext.html#setWidth">setWidth</a>( &amp;p, view.<a href="qrect.html#width">width</a>() );
473 int page = 1;
474 do {
475 richText.<a href="qsimplerichtext.html#draw">draw</a>( &amp;p, margin, margin, view, colorGroup() );
476 view.<a href="qrect.html#moveBy">moveBy</a>( 0, view.<a href="qrect.html#height">height</a>() );
477 p.<a href="qpainter.html#translate">translate</a>( 0 , -view.<a href="qrect.html#height">height</a>() );
478 p.<a href="qpainter.html#drawText">drawText</a>( view.<a href="qrect.html#right">right</a>() - p.<a href="qpainter.html#fontMetrics">fontMetrics</a>().width( QString::<a href="qstring.html#number">number</a>( page ) ),
479 view.<a href="qrect.html#bottom">bottom</a>() + p.<a href="qpainter.html#fontMetrics">fontMetrics</a>().ascent() + 5, QString::number( page ) );
480 if ( view.<a href="qrect.html#top">top</a>() - margin &gt;= richText.<a href="qsimplerichtext.html#height">height</a>() )
481 break;
482 printer-&gt;<a href="qprinter.html#newPage">newPage</a>();
483 page++;
484 } while (TRUE);
485
486 <a href="qmainwindow.html#statusBar">statusBar</a>()-&gt;message( "Printing completed", 2000 );
487 } else {
488 <a href="qmainwindow.html#statusBar">statusBar</a>()-&gt;message( "Printing aborted", 2000 );
489 }
490 }
491</pre>
492<p> <em>print()</em> is called by the <em>File|Print</em> menu item and the <em>filePrint</em>
493tool button.
494<p> We present the user with the print setup dialog, and abandon printing
495if they cancel.
496<p> We create a <a href="qsimplerichtext.html">QSimpleRichText</a> object and give it the text. This object
497is able to format the text nicely as one long page. We achieve
498pagination by printing one paper page's worth of text from the
499QSimpleRichText page at a time.
500<p> Now let's see what happens when a user wishes to <em>close()</em>
501an <em>ApplicationWindow</em>.
502<p> <a name="closeEvent"></a>
503<pre> void ApplicationWindow::<a href="qwidget.html#closeEvent">closeEvent</a>( <a href="qcloseevent.html">QCloseEvent</a>* ce )
504 {
505</pre>
506<p> This event gets to process window system close events. A close event is
507subtly different from a hide event: hide often means "iconify" whereas
508close means that the window is going away for good.
509<p> <pre> if ( !e-&gt;<a href="qtextedit.html#isModified">isModified</a>() ) {
510 ce-&gt;<a href="qcloseevent.html#accept">accept</a>();
511 return;
512 }
513</pre>
514<p> If the text hasn't been edited, we just accept the event. The window
515will be closed, and because we used the <em>WDestructiveClose</em> <a href="qt.html#WidgetFlags">widget flag</a> in the <a href="#ApplicationWindow"><i>ApplicationWindow()</i> constructor</a>,
516the widget will be deleted.
517<p> <pre> switch( QMessageBox::<a href="qmessagebox.html#information">information</a>( this, "Qt Application Example",
518 "Do you want to save the changes"
519 " to the document?",
520 "Yes", "No", "Cancel",
521 0, 1 ) ) {
522</pre>
523<p> Otherwise we ask the user: What do you want to do?
524<p> <pre> case 0:
525 save();
526 ce-&gt;<a href="qcloseevent.html#accept">accept</a>();
527 break;
528</pre>
529<p> If they want to save and then exit, we do that.
530<p> <pre> case 1:
531 ce-&gt;<a href="qcloseevent.html#accept">accept</a>();
532 break;
533</pre>
534<p> If the user doesn't want to exit, we ignore the close event (there is
535a chance that we can't block it but we try).
536<p> <pre> case 2:
537 default: // just for sanity
538 ce-&gt;<a href="qcloseevent.html#ignore">ignore</a>();
539 break;
540</pre>
541<p> The last case -- the user wants to abandon the edits and exit -- is very
542simple.
543<p> <pre> }
544 }
545</pre>
546<p> Last but not least we implement the slots used by the help menu entries.
547<p> <pre> void ApplicationWindow::about()
548 {
549 QMessageBox::<a href="qmessagebox.html#about">about</a>( this, "Qt Application Example",
550 "This example demonstrates simple use of "
551 "QMainWindow,\nQMenuBar and QToolBar.");
552 }
553
554 void ApplicationWindow::aboutQt()
555 {
556 QMessageBox::<a href="qmessagebox.html#aboutQt">aboutQt</a>( this, "Qt Application Example" );
557 }
558</pre>
559<p> These two slots use ready-made "about" functions to provide some
560information about this program and the GUI toolkit it uses. (Although you
561don't need to provide an About Qt in your programs, if you use Qt for free
562we would appreciate it if you tell people what you're using.)
563<p> That was all we needed to write a complete, almost useful application with
564nice help-functions, almost as good as the "editors" some computer vendors
565ship with their desktops, and in less than 300 lines of code!
566<p> <p>See also <a href="step-by-step-examples.html">Step-by-step Examples</a>.
567
568<!-- eof -->
569<p><address><hr><div align=center>
570<table width=100% cellspacing=0 border=0><tr>
571<td>Copyright &copy; 2007
572<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
573<td align=right><div align=right>Qt 3.3.8</div>
574</table></div></address></body>
575</html>
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