29.1. Understanding WPF's Graphical Rendering Services

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 ...

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