Simple .NET/ASP.NET PDF document editor web control SDK

QXmlSimpleReader reader; reader.setContentHandler( &handler ); reader.parse( source ); file.close(); return 0; } The declaration of the handler class MyHandler can be seen in Listing 8-17. The class inherits from QXmlDefaultHandler, which is derived from QXmlContentHandler. The benefit of inheriting QXmlDefaultHandler is that the default handler class provides dummy implementations of all the methods that you otherwise would have had to implement as stubs. The methods in the handler class get called by the reader when something is encountered. You want to handle text and tags and know when the parsing process starts and ends, so the methods shown in the class declaration have been implemented. All methods return a bool value, which is used to stop the parsing if an error is encountered. All methods must return true for the reader to continue reading. Listing 8-17. The MyHandler SAX handler class class MyHandler : public QXmlDefaultHandler { public: bool startDocument(); bool endDocument(); bool startElement( const QString &namespaceURI, const QString &localName, const QString &qName, const QXmlAttributes &atts ); bool endElement( const QString &namespaceURI, const QString &localName, const QString &qName ); bool characters( const QString &ch ); }; All methods except startElement look more or less like the method shown in Listing 8-18. A simple text is printed to the debug console, and then true is returned. In the case of endElement (shown in the listing), an argument is printed as well. Listing 8-18. A simple handling class method bool MyHandler::endElement( const QString &namespaceURI, const QString &localName, const QString &qName ) { qDebug() << "End of element" << qName; return true; }

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Arthur Arthur Arthur Arthur Arthur Arthur is is is is is is at at at at at at (0,0) and is pointing at angle 0.00 radians. (0,10) and is pointing at angle 0.00 radians. (0,10) and is pointing at angle 1.57 radians. (-25,10) and is pointing at angle 1.57 radians. (-25,10) and is pointing at angle 0.79 radians. (-27.5,7.5) and is pointing at angle 0.79 radians.

OK, that seems fine for basic operation. But what happens if we change the width of the platform to zero

Turtle arthurTheTurtle = new Turtle { PlatformWidth = 0.0, PlatformHeight = 10.0, MotorSpeed = 5.0 };

The startElement method, shown in Listing 8-19, is slightly more complex. First, the element s name is printed; then the list of attributes passed through an QXmlAttributes object is printed. The QXmlAttributes is not a standard container, so you must iterate through it using an index variable instead of just using the foreach macro. Before the method ends, you return true to tell the reader that everything is working as expected. Listing 8-19. The startElement method lists the attributes of the element. bool MyHandler::startElement( const QString &namespaceURI, const QString &localName, const QString &qName, const QXmlAttributes &atts ) { qDebug() << "Start of element" << qName; for( int i=0; i<atts.length(); ++i ) qDebug() << " " << atts.qName(i) << "=" << atts.value(i); return true; } The reason for printing the qName instead of the namespaceURI or localName is that the qName is the tag name that you expect. Namespaces and local names are beyond the scope of this book. It is not very complicated to build an XML parser by implementing a SAX handler. As soon as you want to convert the XML data into custom data for your application, you should consider using SAX. Because the entire document is not loaded at once, the memory requirements of the application are reduced, which might mean that your application runs more quickly.

Not only does that not make much sense, but the output is not very useful either; clearly we have divide-by-zero problems:

The Atlas wiki application is a reference application that demonstrates what a fully featured ASP.NET 2.0 application looks like and how it can be enhanced using Atlas.

Arthur Arthur Arthur Arthur Arthur Arthur is is is is is is at at at at at at (0,0) and is pointing at angle 0.00 radians. (0,10) and is pointing at angle 0.00 radians. (0,10) and is pointing at angle Infinity radians. (NaN,NaN) and is pointing at angle Infinity radians. (NaN,NaN) and is pointing at angle NaN radians. (NaN,NaN) and is pointing at angle NaN radians.

Clearly, our real-world turtle could go badly wrong if we told it to rotate through an infinite angle. At the very least, we d get bored waiting for it to finish. We should prevent the user from running it if the PlatformWidth is less than or equal to zero. Previously, we used the following code:

You learned in 4 that the setup with a isSafeToClose and the closeEvent method was a good starting point for giving the user the option to save the file when a window with a modified document is closed. Now the time has come to add support for that functionality to the SDI application (the same concept also applies to the MDI application). Starting with Listing 8-20, you can see the changes made to the SdiWindow class declaration. The highlighted lines were added to handle the load and save functionality. The change is made to add the menu items Open, Save, and Save As to the File menu. The changes to the class declaration consist of four parts: actions for handling the menu entries, slots for the actions, the functions loadFile and saveFile for loading and saving the document to an actual file, and the private variable currentFilename for keeping the current file name. All methods that have to do with saving documents return a bool value, telling the caller whether the document was saved. Listing 8-20. Changes made to the SdiWindow class to enable loading and saving documents class SdiWindow : public QMainWindow { Q_OBJECT

// Run the turtle for the specified duration public void RunFor(double duration) {

if (PlatformWidth <= 0.0) { // What to do here } } // ...