WPF Graphical Rendering Options
WPF uses a particular flavor of graphical rendering that goes by the term retained-mode graphics.Simply put, this means that as you are using XAML or procedural code to generate graphical renderings, it is the responsibility of WPF to persist these visual items and ensure they are correctly redrawn and refreshed in an optimal manner. Thus, when you render graphical data, it is always present, even when the end user hides the image by resizing or minimizing the window, by covering the window with another, and so forth.
In stark contrast, previous Microsoft graphical rendering APIs (including Windows Form’s GDI+) were immediate-mode graphical systems. In this model, it was up to the programmer to ensure that rendered visuals were correctly “remembered” and updated during the life of the application. For example, in a Windows Forms application, rendering a shape such as a rectangle involved handling the Paintevent (or overriding the virtual OnPaint()method), obtaining a Graphics object to draw the rectangle and, most important, adding the infrastructure to ensure that the image was persisted when the user resized the window (for example, creating member variables to represent the position of the rectangle and calling Invalidate()throughout your program).
In stark contrast, previous Microsoft graphical rendering APIs (including Windows Form’s GDI+) were immediate-mode graphical systems. In this model, it was up to the programmer to ensure that rendered visuals were correctly “remembered” and updated during the life of the application. For example, in a Windows Forms application, rendering a shape such as a rectangle involved handling the Paintevent (or overriding the virtual OnPaint()method), obtaining a Graphics object to draw the rectangle and, most important, adding the infrastructure to ensure that the image was persisted when the user resized the window (for example, creating member variables to represent the position of the rectangle and calling Invalidate()throughout your program).
- Shapes
- WPF provides the System.Windows.Shapes namespace, which defines a small number of classes for rendering 2D geometric objects (rectangles, ellipses, polygons, etc.). While these types are very simple to use, and very powerful, they do come with a fair amount of memory overhead if used with reckless abandon.
- Drawings and Geometries
- The WPF API provides a second way to render graphical data, using descendants from the System.Windows.Media.Drawing abstract class. Using classes such as GeometryDrawing or ImageDrawing(in addition to various geometry objects) you can render graphical data in a more lightweight (but less feature-rich) manner.
- Visuals
- The fastest and most lightweight way to render graphical data under WPF is using the visual layer, which is accessible only through C# code. Using descendants ofSystem.Windows.Media.Visual, you can speak directly to the WPF graphical subsystem.
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