QTextLayout Class Reference
[QtGui module]

Detailed Description

The QTextLayout class is used to lay out and paint a single paragraph of text.

It offers most features expected from a modern text layout engine, including Unicode compliant rendering, line breaking and handling of cursor positioning. It can also produce and render device independent layout, something that is important for WYSIWYG applications.

The class has a rather low level API and unless you intend to implement your own text rendering for some specialized widget, you probably won't need to use it directly.

QTextLayout can currently deal with plain text and rich text paragraphs that are part of a QTextDocument.

QTextLayout can be used to create a sequence of QTextLine's with given widths and can position them independently on the screen. Once the layout is done, these lines can be drawn on a paint device.

Here's some pseudo code that presents the layout phase:

 int leading = fontMetrics.leading();
 qreal height = 0;
 qreal widthUsed = 0;
 textLayout.beginLayout();
 while (1) {
     QTextLine line = textLayout.createLine();
     if (!line.isValid())
         break;

     line.setLineWidth(lineWidth);
     height += leading;
     line.setPosition(QPointF(0, height));
     height += line.height();
     widthUsed = qMax(widthUsed, line.naturalTextWidth());
 }
 textLayout.endLayout();

The text can be drawn by calling the layout's draw() function:

 QPainter painter(this);
 textLayout.draw(&painter, QPoint(0, 0));

The text layout's text is set in the constructor or with setText(). The layout can be seen as a sequence of QTextLine objects; use lineAt() or lineForTextPosition() to get a QTextLine, createLine() to create one. For a given position in the text you can find a valid cursor position with isValidCursorPosition(), nextCursorPosition(), and previousCursorPosition(). The layout itself can be positioned with setPosition(); it has a boundingRect(), and a minimumWidth() and a maximumWidth(). A text layout can be drawn on a painter device using draw().

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