Qt Introduction. Topics. C++ Build Process. Ch & Ch 3. 1) What's Qt? 2) How can we make a Qt console program? 3) How can we use dialogs?

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1 Topics Qt Introduction Ch & Ch 3 1) What's Qt? 2) How can we make a Qt console program? 3) How can we use dialogs? Q: How do you pronounce Qt? A: This puppy is... 23/01/12 CMPT 212 Slides #5 Dr. B. Fraser 1 23/01/12 2 Qt C++ Build Process or.obj Qt is: car.cpp Header file Inserted Compiled Features: Strong GUI creation. Extends C++ (object communication) Example Applications: Google Earth K Desktop Environment car.h main.cpp car.h Preprocessor Preprocessor Header file Inserted Compiler Compiled Compiler gcc.lib Linker 23/01/ /01/12 4

2 Qt Build Tools Qt Creator Create a Qt Project File (.pro) > qmake -project Note: For console applications, add this to the.pro file: CONFIG += console Create a Makefile > qmake Build the application > make qmake -project myapp.pro qmake Makefile make Qt Creator IDE in Qt SDK: C++/Qt Coding (context sensitive help, syntax highlighting, code-completion) Designing GUIs Debugging Demo: Creating new project, adding a class, importing code. Changing project settings, editing.pro file. 23/01/12 Build Demo 5 23/01/ Hello Qt World Qt uses.. : for, if, while, class,... Qt has.. string QString Qt Basics and using "cin" & "cout" vector QVector iostream/iostringstream QTextStream ifstream/ofstream QFile & QTextStream Moving to Qt For each STL class, we'll be moving to Qt. We will quickly not need.. 23/01/ /01/12 8

3 cout/cin/cerr Linkage Replacing cout/cin cout/cin/cerr are in the std namespace. Part of the iostream library. C provides i/o file access: stdout, stdin, stderr Linkage refers to 'share-ability' of items across files: Internal Linkage: Identifier = function or variable. Replace cout/cin with QTextStream's: Two.cpp files may independently define the same identifier. External Linkage: Name conflict if two files declare same identifier. One Definition Rule: 23/01/ /01/12 10 External Linkage Example linkage1.cpp linkage2.cpp extern linkage1.cpp linkage2.cpp void foo() cout << "I pity the FOO!" << endl; ; int main() //... void foo() cout << "I pity the FOO!" << endl; ; g_badidea and foo() both... void foo() cout << "I pity the FOO!" << endl; ; Add extern to change a into a Create the variable & function. extern int g_badidea; extern void foo(); Use variable & function defined in other file. void bar() foo(); cout << "0: " << ZERO << endl; cout << "1: " << g_badidea << endl; ; linkage2.obj : error LNK2005: "void cdecl foo(void)" (?foo@@yaxxz) already defined in linkage1.obj linkage2.obj : error LNK2005: "int badidea" (?badidea@@3ha) already defined in linkage1.obj 23/01/12 11 Only one 'instance' created, but other file can use it. 23/01/12 12

4 Static & Linkage Summary Changing External to Internal Add static to a function or variable definition to.. Makes it so 2 files can independently declare variables/functions.. linkage1.cpp void foo() ; //... Linkage Summary: linkage2.cpp static static void foo() ; //... Internal Linkage External Linkage Functions Static Functions Normal Functions Variables Static "Global" Variables Global Variables this g_badidea and foo() have.. Constants 23/01/12 13 Back to Qt vs cout What's wrong with this? main.cpp #include <QTextStream> QTextStream cout(stdout); QTextStream cin(stdin); int main() Cake dinner(); dinner.eat(); cout << "Mmmm Good." << endl; cake.h class Cake public: void eat(); ; cake.cpp #include <QTextStream> QTextStream cout(stdout); QTextStream cin(stdin); void Cake::eat() cout << "Munch Munch" << endl; 23/01/12 14 Solution: std2qt C-Library std2qt.h std2qt.cpp #ifndef STD2QT_H #define STD2QT_H #include <QTextStream> namespace std2qt extern QTextStream cout; extern QTextStream cin; extern QTextStream cerr; ; #endif #include "std2qt.h" QTextStream std2qt::cout(stdout); QTextStream std2qt::cin(stdin); QTextStream std2qt::cerr(stderr); #include "std2qt.h" using namespace std2qt; int main() Cake dinner(); dinner.eat(); cout << "Mmmm Good." << endl; void Cake::eat() cout << "Munch Munch" << endl; 23/01/12 15 cake.cpp cake.h main.cpp class Cake public: void eat(); ; #include "std2qt.h" using namespace std2qt; STD to Qt Replacement Classes 23/01/12 16

5 QString Ch1.8 More on QTextStream Ch1.9 Supports Unicode Richer API, easier to use Interacts well with rest of Qt #include <QString> int main() QString hi("hello"); QString world = "World"; int len = hi.length(); QChar qletter = hi[0]; char ch = qletter.toascii(); QString both = hi + " " + world; if (hi == "Hello") hi = "bye"; Very similar to std::string interface. hi[0] returns a QChar, not a char! 23/01/12 See documentation for more. 17 This slide assumes cin/cout are our custom QTextStream objects! Read a line of text: QString name = Output "flushed" at new line; force with flush: cout << "Your name: " << flush; Some modifiers are different: qsetfieldwidth(10) vs setw() qsetrealnumberprecision() vs setprecision() Ex: cout << left << qsetfieldwidth(10) << "Height: " << qsetrealnumberprecision(2) << ; 23/01/12 See documentation for more. 18 QFile Ch1.10 QFile Handles file management Input/output done through.. #include <QFile> int main() // Data to write QString name = "Dr. Evil"; int favnum = 42; QTextStream constructor takes QFile pointer (&). // Open the file QFile writefile("test.txt"); writefile.open(qiodevice::writeonly); // Write to the file through a QTextStream QTextStream filetxtstream(&writefile); filetxtstream << "Hello " << name << favnum << endl; filetxtstream << "The end!\n"; Ready-Made Qt Dialogs // Close the file writefile.close(); 23/01/ /01/12 20

6 Qt Dialogs Ch1.11 Qt Dialogs Ch1.11 #include <QtGui> const int NO_PARENT = 0; const char *APP_NAME = "Qt Dialog Demo"; int main(int argc, char *argv[]) // Support graphical applications QApplication app(argc, argv); Use Qt's GUI features. Graphical Qt applications need a QApplication. // Continued from previous... // Output QString message = QString("Nice name, %1!").arg(name); QMessageBox::information( message); Can build up QStrings: substitute the %1 %2... // Get a number int favnum = QInputDialog::getInt( "What is your favourite number?"); // Get a string QString name = QInputDialog::getText( "What is your name?"); // Input int answer = QMessageBox::question( "Do you know binary?", QMessageBox::Yes QMessageBox::No); if (answer == QMessageBox::Yes) // Do something here... // More... 23/01/12 21 return 0; 23/01/12 QtDialogDemo & QtDialogFactorial (Refactor?) 22 Summary Qt will largely replace STD library for us. Linkage: External Linkage: Sharable between files. Internal Linkage: Not sharable between files. Use a QTextStream to: Replace cin, cout, cerr Build a string Write to/read from a file Qt has ready-made dialogs which are quick to use. 23/01/12 23