The Scribe Classes

Manipulating Rich Text

Rich text is stored in text documents that can either be created by importing HTML from an external source, or generated using a QTextCursor. The easiest way to use a rich text document is through the QTextEdit class, providing an editable view onto a document. The code below imports HTML into a document, and displays the document using a text edit widget.

     QTextEdit *editor = new QTextEdit(parent);
     editor->setHtml(aStringContainingHTMLtext);
     editor->show();

You can retrieve the document from the text edit using the document() function. The document can then be edited programmatically using the QTextCursor class. This class is modeled after a screen cursor, and editing operations follow the same semantics. The following code changes the first line of the document to a bold font, leaving all other font properties untouched. The editor will be automatically updated to reflect the changes made to the underlying document data.

     QTextDocument *document = edit->document();
     QTextCursor cursor(document);

     cursor.movePosition(QTextCursor::Start);
     cursor.movePosition(QTextCursor::EndOfLine, QTextCursor::KeepAnchor);

     QTextCharFormat format;
     format.setFontWeight(QFont::Bold);

     cursor.mergeCharFormat(format);

Note that the cursor was moved from the start of the first line to the end, but that it retained an anchor at the start of the line. This demonstrates the cursor-based selection facilities of the QTextCursor class.

Rich text can be generated very quickly using the cursor-based approach. The following example shows a simple calendar in a QTextEdit widget with bold headers for the days of the week:

     editor = new QTextEdit(this);

     QTextCursor cursor(editor->textCursor());
     cursor.movePosition(QTextCursor::Start);

     QTextCharFormat format(cursor.charFormat());
     format.setFontFamily("Courier");

     QTextCharFormat boldFormat = format;
     boldFormat.setFontWeight(QFont::Bold);

     cursor.insertBlock();
     cursor.insertText(" ", boldFormat);

     QDate date = QDate::currentDate();
     int year = date.year(), month = date.month();

     for (int weekDay = 1; weekDay <= 7; ++weekDay) {
         cursor.insertText(QString("%1 ").arg(QDate::shortDayName(weekDay), 3),
             boldFormat);
     }

     cursor.insertBlock();
     cursor.insertText(" ", format);

     for (int column = 1; column < QDate(year, month, 1).dayOfWeek(); ++column) {
         cursor.insertText("    ", format);
     }

     for (int day = 1; day <= date.daysInMonth(); ++day) {
         int weekDay = QDate(year, month, day).dayOfWeek();

         if (QDate(year, month, day) == date)
             cursor.insertText(QString("%1 ").arg(day, 3), boldFormat);
         else
             cursor.insertText(QString("%1 ").arg(day, 3), format);

         if (weekDay == 7) {
             cursor.insertBlock();
             cursor.insertText(" ", format);
         }
     }

The above example demonstrates how simple it is to quickly generate new rich text documents using a minimum amount of code. Although we have generated a crude fixed-pitch calendar to avoid quoting too much code, Scribe provides much more sophisticated layout and formatting features.

     QTextLayout textLayout(text, font);
     qreal margin = 10;
     qreal radius = qMin(width()/2.0, height()/2.0) - margin;
     QFontMetrics fm(font);

     qreal lineHeight = fm.height();
     qreal y = 0;

     textLayout.beginLayout();

     while (1) {
         // create a new line
         QTextLine line = textLayout.createLine();
         if (!line.isValid())
             break;

         qreal x1 = qMax(0.0, pow(pow(radius,2)-pow(radius-y,2), 0.5));
         qreal x2 = qMax(0.0, pow(pow(radius,2)-pow(radius-(y+lineHeight),2), 0.5));
         qreal x = qMax(x1, x2) + margin;
         qreal lineWidth = (width() - margin) - x;

         line.setLineWidth(lineWidth);
         line.setPosition(QPointF(x, margin+y));
         y += line.height();
     }

     textLayout.endLayout();

     QPainter painter;
     painter.begin(this);
     painter.setRenderHint(QPainter::Antialiasing);
     painter.fillRect(rect(), Qt::white);
     painter.setBrush(QBrush(Qt::black));
     painter.setPen(QPen(Qt::black));
     textLayout.draw(&painter, QPoint(0,0));

     painter.setBrush(QBrush(QColor("#a6ce39")));
     painter.setPen(QPen(Qt::black));
     painter.drawEllipse(QRectF(-radius, margin, 2*radius, 2*radius));
     painter.end();

     QTextDocument *document = editor->document();
     QPrinter printer;

     QPrintDialog *dlg = new QPrintDialog(&printer, this);
     if (dlg->exec() != QDialog::Accepted)
         return;

     document->print(&printer);

     QString fileName = QFileDialog::getSaveFileName(this, "Export PDF",
                                                     QString(), "*.pdf");
     if (!fileName.isEmpty()) {
         if (QFileInfo(fileName).suffix().isEmpty())
             fileName.append(".pdf");
         QPrinter printer(QPrinter::HighResolution);
         printer.setOutputFormat(QPrinter::PdfFormat);
         printer.setOutputFileName(fileName);
         textEdit->document()->print(&printer);
     }