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author | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-11-08 12:31:36 -0600 |
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committer | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-11-08 12:31:36 -0600 |
commit | d796c9dd933ab96ec83b9a634feedd5d32e1ba3f (patch) | |
tree | 6e3dcca4f77e20ec8966c666aac7c35bd4704053 /doc/application-walkthrough.doc | |
download | tqt3-d796c9dd933ab96ec83b9a634feedd5d32e1ba3f.tar.gz tqt3-d796c9dd933ab96ec83b9a634feedd5d32e1ba3f.zip |
Test conversion to TQt3 from Qt3 8c6fc1f8e35fd264dd01c582ca5e7549b32ab731
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diff --git a/doc/application-walkthrough.doc b/doc/application-walkthrough.doc new file mode 100644 index 000000000..e3a5aa6a8 --- /dev/null +++ b/doc/application-walkthrough.doc @@ -0,0 +1,435 @@ +/**************************************************************************** +** +** Application example documentation +** +** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved. +** +** This file is part of the Qt GUI Toolkit. +** +** This file may be used under the terms of the GNU General +** Public License versions 2.0 or 3.0 as published by the Free +** Software Foundation and appearing in the files LICENSE.GPL2 +** and LICENSE.GPL3 included in the packaging of this file. +** Alternatively you may (at your option) use any later version +** of the GNU General Public License if such license has been +** publicly approved by Trolltech ASA (or its successors, if any) +** and the KDE Free Qt Foundation. +** +** Please review the following information to ensure GNU General +** Public Licensing retquirements will be met: +** http://trolltech.com/products/qt/licenses/licensing/opensource/. +** If you are unsure which license is appropriate for your use, please +** review the following information: +** http://trolltech.com/products/qt/licenses/licensing/licensingoverview +** or contact the sales department at sales@trolltech.com. +** +** This file may be used under the terms of the Q Public License as +** defined by Trolltech ASA and appearing in the file LICENSE.QPL +** included in the packaging of this file. Licensees holding valid Qt +** Commercial licenses may use this file in accordance with the Qt +** Commercial License Agreement provided with the Software. +** +** This file is provided "AS IS" with NO WARRANTY OF ANY KIND, +** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR +** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted +** herein. +** +**********************************************************************/ + +/*! +\page simple-application.html + +\ingroup step-by-step-examples + +\title Walkthrough: A Simple Application + +This walkthrough shows simple use of \l QMainWindow, \l QMenuBar, \l +QPopupMenu, \l QToolBar and \l QStatusBar - classes that every +modern application window tends to use. (See also \link tutorial2.html +Tutorial #2\endlink.) + +It also illustrates some aspects of \l QWhatsThis (for simple help) and a +typical \c main() using \l QApplication. + +Finally, it shows a typical print function based on \l QPrinter. + +\section1 The declaration of ApplicationWindow + +Here's the header file in full: + +\include application/application.h + +It declares a class that inherits \l QMainWindow, with slots and private +variables. The class pre-declaration of \l QTextEdit at the beginning +(instead of an include) helps to speed up compilation. With this +trick, \c{make depend} won't insist on recompiling every \c .cpp file that +includes \c application.h when \c qtextedit.h changes. + +\target simplemain +\section1 A simple main() + +Here is \c main.cpp in full: + +\include application/main.cpp + +Now we'll look at \c main.cpp in detail. + +\quotefile application/main.cpp +\skipto argc +\printline argc +\printline QApplication + +With the above line, we create a QApplication object with the usual +constructor and let it +parse \e argc and \e argv. QApplication itself takes care of X11-specific +command-line options like \e -geometry, so the program will automatically +behave the way X clients are expected to. + +\printline ApplicationWindow +\printline setCaption +\printline show + +We create an \e ApplicationWindow as a top-level widget, set its window +system caption to "Document 1", and \e show() it. + +\target close +\printline connect + +When the application's last window is closed, it should tquit. Both +the signal and the slot are predefined members of QApplication. + +\printline exec + +Having completed the application's initialization, we start the main +event loop (the GUI), and eventually return the error code +that QApplication returns when it leaves the event loop. + +\printline } + +\target ApplicationWindow +\section1 The Implementation of ApplicationWindow + +\quotefile application/application.cpp + +Since the implementation is tquite large (almost 300 lines) we +won't list the whole thing. (The source code is included in the +examples/application directory.) Before we start with the constructor +there are three \c{#include}s worth mentioning: + +\skipto "filesave.xpm" +\printuntil "fileprint.xpm" + +The tool buttons in our application wouldn't look good without icons! +These icons can be found in the XPM files included above. If you ever +moved a program to a different location and wondered why icons were +missing afterwards you will probably agree that it is a good idea to +compile them into the binary. This is what we are doing here. + +\skipto ApplicationWindow::ApplicationWindow +\printline ApplicationWindow::ApplicationWindow +\printuntil { + +\e ApplicationWindow inherits QMainWindow, the Qt class that provides +typical application main windows, with menu bars, toolbars, etc. + +\printuntil QPrinter + +The application example can print things, and we chose to have a +QPrinter object lying around so that when the user changes a setting +during one printing, the new setting will be the default next time. + +\printline QPixmap + +For the sake of simplicity, our example only has a few commands in the +toolbar. The above variables are used to hold an icon for each of +them. + +\printline QToolBar + +We create a toolbar in \e this window ... + +\printline "File Operations" + +... and define a title for it. When a user drags the toolbar out of +its location and floats it over the desktop, the toolbar-window will +show "File Operations" as caption. + +\printline fileopen +\printuntil SLOT(choose()) + +Now we create the first tool button for the \e fileTools toolbar +with the appropriate icon and the tool-tip text "Open File". +The \c fileopen.xpm we included at the beginning +contains the definition of a pixmap called \e fileopen. +We use this icon to illustrate our first tool button. + +\printuntil SLOT(print()) + +In a similar way we create two more tool buttons in this toolbar, each with +appropriate icons and tool-tip text. All three buttons are connected +to appropriate slots in this object; for example, the "Print File" button +to \link #printer ApplicationWindow::print()\endlink. + +\printline whatsThisButton + +The fourth button in the toolbar is somewhat peculiar: it's the one that +provides "What's This?" help. This must be set up using a special +function, as its mouse interface is unusual. + +\printuntil fileOpenText ) + +With the above line we add the "What's This?" help-text to the +\e fileOpen button... + +\printline openIcon + +... and tell the rich-text engine that when a help-text (like the one +saved in \e fileOpenText) requests an image named "fileopen", the \e +openIcon pixmap is used. + +\printuntil fileSaveText ) +\printuntil filePrintText ) + +The "What's This?" help of the remaining two buttons doesn't make use +of pixmaps, therefore all we need to do is to add the help-text to the +button. Be careful though: To invoke the rich-text elements in \c +fileSaveText(), the entire string must be surrounded by \<p\> and +\</p\>. In \c filePrintText(), we don't have rich-text elements, so +this is not necessary. + +\printuntil &File + +Next we create a \l QPopupMenu for the \e File menu and +add it to the menu bar. With the ampersand in front of the letter F, +we allow the user to use the shortcut \e Alt+F to pop up this menu. + +\printline &New + +Its first entry is connected to the (yet to be implemented) slot \c +newDoc(). When the user chooses this \e New entry (e.g. by typing the +letter N as marked by the ampersand) or uses the +\e Ctrl+N accelerator, a new editor-window will pop up. + +\printuntil &Open +\printuntil &Save +\printuntil Save &As +\printuntil fileSaveText + +We populate the \e File menu with three more commands (\e Open, \e Save and +\e{Save As}), and set "What's This?" help for them. Note in particular +that "What's This?" help and pixmaps are used in both the toolbar (above) +and the menu bar (here). (See QAction and the \c examples/action +example for a shorter and easier approach.) + +\printline insertSeparator( + +Then we insert a separator, ... + +\printline &Print +\printuntil &Close +\printline &Quit + +... the \e Print command with "What's This?" help, another separator and +two more commands (\e Close and \e Quit) without "What's This?" and pixmaps. +In case of the \e Close command, the signal is connected +to the \e close() slot of the respective \e ApplicationWindow object whilst +the \e Quit command affects the entire application. + +Because \e ApplicationWindow is a QWidget, the \e close() function +triggers a call to \link #closeEvent closeEvent()\endlink which we +will implement later. + +\target common_constructor +\printline insertSeparator + +Now that we have done the File menu we shift our focus back to the +menu bar and insert a separator. From now on further menu bar entries +will be aligned to the right if the windows system style retquires it. + +\printline help +\printuntil whatsThis + +We create a \e Help menu, add it to the menu bar, and insert a few +commands. Depending on the style it will appear on the right hand +side of the menu bar or not. + +\printline QTextEdit +\printline setFocus +\printline setCentralWidget + +Now we create a simple text-editor, set the initial focus to it, +and make it the window's central widget. + +\l QMainWindow::centralWidget() is the heart of the entire application: +It's what menu bar, statusbar and toolbars are all arranged around. Since +the central widget is a text editing widget, we can now reveal that +our simple application is a text editor. :) + +\printline "Ready" + +We make the statusbar say "Ready" for two seconds at startup, just to +tell the user that the window has finished initialization and can be +used. + +\printline resize + +Finally it's time to resize the new window to a a nice default size. + +\printline } + +We have now finished with the constructor. Now we'll deal with the +destructor. + +\printline ::~ +\printuntil } + +The only thing an \e ApplicationWindow widget needs to do in its +destructor is to delete the printer it created. All other objects are +child widgets, which Qt will delete when appropriate. + +Now our task is to implement all the slots mentioned in the header file +and used in the constructor. + +\target newDoc() +\printline ::newDoc +\printuntil } + +This slot, connected to the \e{File|New} menu item, simply creates a +new \e ApplicationWindow and shows it. + +\target choose() +\printline ::choose +\printuntil getOpenFileName +\printuntil } + +The \e choose() slot is connected to the \e Open menu item and +tool button. With a little help from \l QFileDialog::getOpenFileName(), it +asks the user for a file name and then either loads that file or gives an +error message in the statusbar. + +\printline ::load +\printuntil statusBar +\printline } + +This function loads a file into the editor. When it's done, it sets the +window system caption to the file name and displays a success message in +the statusbar for two seconds. With files that exist but are not +readable, nothing happens. + +\target save() +\printline ::save +\printuntil close + +As its name suggests, this function saves the current file. If no +filename has been specified so far, the \link #saveAs() +saveAs()\endlink function is called. Unwritable files cause the \e +ApplicationWindow object to provide an error-message in the statusbar. +Note that there is more than one way to do this: +compare the above \c{statusBar()->message()} line with the equivalent +code in the \c load() function. + +\printline setModified + +Tell the editor that the contents haven't been edited since the last +save. When the user does some further editing and wishes to close the +window without explicit saving, \link #closeEvent +ApplicationWindow::closeEvent()\endlink will ask about it. + +\printline setCaption + +It may be that the document was saved under a different name than the +old caption suggests, so we set the window caption just to be sure. + +\printuntil } + +With a message in the statusbar, we inform the user that the file +was saved successfully. + +\target saveAs() +\printline ::saveAs +\printuntil message +\printline } +\printline } + +This function asks for a new name, saves the document under that name, +and implicitly changes the window system caption to the new name. + +\target printer + +\skipto ::print +\printuntil aborted +\printuntil aborted +\printline } +\printline } + +\e print() is called by the \e{File|Print} menu item and the \e filePrint +tool button. + +We present the user with the print setup dialog, and abandon printing +if they cancel. + +We create a QSimpleRichText object and give it the text. This object +is able to format the text nicely as one long page. We achieve +pagination by printing one paper page's worth of text from the +QSimpleRichText page at a time. + + +Now let's see what happens when a user wishes to \e close() +an \e ApplicationWindow. + +\target closeEvent +\printline ::closeEvent +\printline { + +This event gets to process window system close events. A close event is +subtly different from a hide event: hide often means "iconify" whereas +close means that the window is going away for good. + +\printline isModified +\printline accept +\printline return +\printline } + +If the text hasn't been edited, we just accept the event. The window +will be closed, and because we used the \e WDestructiveClose widget +flag in the \link #ApplicationWindow <i>ApplicationWindow()</i> constructor\endlink, +the widget will be deleted. + +\printline QMessageBox +\printuntil { + +Otherwise we ask the user: What do you want to do? + +\printuntil break + +If they want to save and then exit, we do that. + +\printuntil break + +If the user doesn't want to exit, we ignore the close event (there is +a chance that we can't block it but we try). + +\printuntil break + +The last case -- the user wants to abandon the edits and exit -- is very +simple. + +\printline } +\printline } + +Last but not least we implement the slots used by the help menu entries. + +\printline ::about +\printuntil aboutQt +\printuntil } + +These two slots use ready-made "about" functions to provide some +information about this program and the GUI toolkit it uses. (Although you +don't need to provide an About Qt in your programs, if you use Qt for free +we would appreciate it if you tell people what you're using.) + +That was all we needed to write a complete, almost useful application with +nice help-functions, almost as good as the "editors" some computer vendors +ship with their desktops, and in less than 300 lines of code! + +*/ |