MSDN Magazine - October 2007 - (Page 115)

3D Text in WPF Charles PeTzolD utline font technologies such as TrueType primarily provide us with typographical flexibility and accuracy, but they can also serve as graphical playthings. Programmers can get access to the actual outlines that define each text character and treat them as vector graphics objects. The outlines can be stroked, filled, used for clipping, or subjected to transforms. A popular feature in Microsoft® Word known as WordArt is based on this concept. It’s important to recognize the nature and limitations of these character outlines: they are strictly geometrical and are missing the “hints” that the operating system normally uses to render fonts on the screen. These hints allow the characters to be rasterized intelligently based on the available pixel grid. Consequently, the unhinted character outlines look best in big font sizes or on high-resolution devices. They are usually not adequate for rendering text at normal font sizes on the screen. (However, as printer resolution gets higher and as antialiasing is used more for screen graphics, the value Figure 1 Solid 3D Text of hinting has decreased.) Whenever I encounter a new Windows® API, I make a special effort to locate the provision for getting access to these character outlines. In Windows Forms, it’s part of the GraphicsPath class. Four overloads of an AddString method lets you add character outlines to a path. Chapter 19 of my books Programming Microsoft Windows with C# (Microsoft Press, 2002) and Programming Microsoft Windows with Microsoft Visual Basic® .NET (Microsoft Press, 2003) show how this is done. In Windows Presentation Foundation (WPF), the classes and methods that provide access to character outlines are better hidden, but they do exist. The FormattedText and GlyphRun classes from the System.Windows.Media namespace both have methods named BuildGeometry that return a Geometry object for a particular font and text string. In this article I’ll use FormattedText exclusively because it’s the easier of the two classes. Chapters 28 and 30 of my book Applications = Code + Markup (Microsoft Press, 2006) have some examples of using FormattedText and BuildGeometry with two-dimensional graphics. When I began working with 3D graphics in WPF, I naturally pondered the possibility of turning these character outlines into blocks of three-dimensional text such as seen in printed media and O flying logo effects on television (see the example given in Figure 1). I knew that the job would involve converting a two-dimensional outline into a three-dimensional triangle mesh, but beyond that, I was sure of only one thing: some non-trivial programming was going to be involved. FormattedText and BuildGeometry I suspect that most WPF programmers haven’t had much contact with the FormattedText class. As the documentation indicates, you use this class for “low-level control for drawing text.” The FormattedText constructors require a TypeFace object, which defines the font family, a style (such as italic), possible boldfacing, and any stretching or compression associated with the font. In addition, the FormattedText constructors require an em size (the font height), a brush for coloring the font characters, and the text string itself. Once a FormattedText object is created, you can call various methods to set different fonts, styling, or formatting to subsets of the text string. Properties let you set line spacing and other characteristics of the text. FormattedText objects are used most commonly with the DrawText method of the DrawingContext class. Generally you encounter the DrawingContext class when you override the OnRender method defined by UIElement. This is the lowest level of graphics output your application can do and still be considered a pure WPF application. The DrawText method requires only a FormattedText object and a coordinate point where the text is to begin. In the context of everything else in FormattedText, the BuildGeometry method seems like an oddity. The method has one argument—an origin of type Point—and returns a Geometry object. Geometry is an important class in WPF, and it’s clearly related to the traditional graphics path. A Geometry object is a collection of straight lines and curves specified as coordinate points. Some of these lines and curves might be connected; some connected lines and curves might be closed to describe enclosed areas. No concept of rendering is included in a Geometry object. In two-dimensional graphics programming, you can render a Geometry object by passing it to the handy Path class, which is part of the high-level october2007 115

Table of Contents Feed for the Digital Edition of MSDN Magazine - October 2007

Cover Contents Toolbox CLR Inside Out Basic Instincts Data Points Cutting Edge Pooled Threads WPF Threads Parallel Linq Parallel Performance Mobile Apps Test Run Foundations Windows with C++ Netting C++ .NET Matters { End Bracket } Net Nuptials

MSDN Magazine - October 2007

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