Qt 4.6: Qt Script Tetrix Example

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# Qt Script Tetrix Example

Files:

- script/qstetrix/tetrixboard.cpp
- script/qstetrix/tetrixboard.h
- script/qstetrix/tetrixboard.js
- script/qstetrix/tetrixpiece.js
- script/qstetrix/tetrixwindow.js
- script/qstetrix/tetrixwindow.ui
- script/qstetrix/main.cpp
- script/qstetrix/qstetrix.pro
- script/qstetrix/tetrix.qrc

The QSTetrix example is a Qt Script version of the classic Tetrix game.

## Overview

The program logic in this example is a fairly straight port of the logic in the C++ Tetrix Example. You may find it useful to compare the implementations of the `TetrixBoard`, `TetrixPiece` and `TetrixWindow` classes to see how Qt Script is used to implement methods, call Qt functions, and emit signals.

## Setting up the GUI

The graphical user interface is defined in a UI file, created using Qt Designer, and is set up in the example's C++ `main.cpp` file.

     class TetrixUiLoader : public QUiLoader
     {
     public:
         TetrixUiLoader(QObject *parent = 0)
             : QUiLoader(parent)
             { }
         virtual QWidget *createWidget(const QString &className, QWidget *parent = 0,
                                       const QString &name = QString())
         {
             if (className == QLatin1String("TetrixBoard")) {
                 QWidget *board = new TetrixBoard(parent);
                 board->setObjectName(name);
                 return board;
             }
             return QUiLoader::createWidget(className, parent, name);
         }
     };

We define a custom UI loader that handles our `TetrixBoard` widget; this is the main component of the UI (where the pieces are drawn).

         QApplication app(argc, argv);
         QScriptEngine engine;

         QScriptValue Qt = engine.newQMetaObject(QtMetaObject::get());
         Qt.setProperty("App", engine.newQObject(&app));
         engine.globalObject().setProperty("Qt", Qt);

We initialize the script engine to have the Qt namespace, so that e.g., Qt.Key_Left will be available to script code. We also make the application object available (for the quit() slot).

         evaluateFile(engine, ":/tetrixpiece.js");
         evaluateFile(engine, ":/tetrixboard.js");
         evaluateFile(engine, ":/tetrixwindow.js");

Several scripts are evaluated as part of the engine setup process. The `tetrixpiece.js` file contains the definition of the `TetrixPiece` class, which is used to populate the play field. The `tetrixboard.js` file contains the definition of the `TetrixBoard` class, which contains the main game logic. Finally, `tetrixwindow.js` contains the definition of the `TetrixWindow` class, which wires up the top-level widget.

         TetrixUiLoader loader;
         QFile uiFile(":/tetrixwindow.ui");
         uiFile.open(QIODevice::ReadOnly);
         QWidget *ui = loader.load(&uiFile);
         uiFile.close();

         QScriptValue ctor = engine.evaluate("TetrixWindow");
         QScriptValue scriptUi = engine.newQObject(ui, QScriptEngine::ScriptOwnership);
         QScriptValue tetrix = ctor.construct(QScriptValueList() << scriptUi);

A form is created from the UI file. A new `TetrixWindow` script object is then constructed, passing the form as its argument.

         ui->resize(550, 370);
         ui->show();

         qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));
         return app.exec();

The form is shown, and the event loop is entered.